Detailed Island Risk Assessment in Maldives

Transcription

1 Detailed Island Risk Assessment in Maldives Volume III: Detailed Island Reports Dh. Kudahuvadhoo Part 1 DIRAM team Disaster Risk Management Programme UNDP Maldives December 2007

2 Table of contents 1. Geographic background 1.1 Location 1.2 Physical Environment 2. Natural hazards 2.1 Historic events 2.2 Major hazards 2.3 Event Scenarios 2.4 Hazard zones 2.5 Recommendation for future study 3. Environment Vulnerabilities and Impacts 3.1 General environmental conditions 3.2 Environmental mitigation against historical hazard events 3.3 Environmental vulnerabilities to natural hazards 3.4 Environmental assets to hazard mitigation 3.5 Predicted environmental impacts from natural hazards 3.6 Findings and recommendations for safe island development 3.7 Recommendations for further study 4. Structural vulnerability and impacts 4.1 House vulnerability 4.2 Houses at risk 4.3 Critical facilities at risk 4.4 Functioning impacts 4.5 Recommendations for risk reduction

3 1. Geographic background 1.1 Location Kudahuvadhoo is located on the southern end of South Nilandhe Atoll (Dhaalu Atoll), next to the Kudahuvadhoo Kanduolhi (reef pass) at approximately 73 39' 3"E and 4 22' 28" N (Figure 1.1). It is located at about 181 km from the nation s capital Male and about 113 km from the nearest Airport Laamu Atoll, Kadhoo. Kudahuvadhoo is the Atoll Capital of Dhaalu Atoll, amongst a group of 7 inhabited islands. It s nearest inhabited islands are Maaenboodhoo (8 km), and Vaanee (13 km). Dhaalu atoll is located along the western line of atolls. 3 00' N Meedhoo Ban'didhoo Rin'budhoo Hulhudheli South Nilandhe Atoll (Dhaalu Atoll) 2 45' N N Kudahuvadhoo Vaanee Maaen'boodhoo 73 00' E Location Map of Kudahuvadhoo 0 5 kilometers 10 Figure 1.1 Location map of Kudahuvadhoo. 1.2 Physical Environment Kudahuvadhoo is a fairly large island with a length of 1040m and a width of 880 m at its widest point. The total surface area of the island is 69.7 Ha (0.69 km 2 ). The reef of Kudahuvadhoo is one of largest in Maldives with a surface area of 5601 Ha (56.01 km 2 ). The reef also hosts 3 other uninhabited islands.

4 Kudahuvadhoo is located at the southern tip of the reef system, approximately 450m from the southern wave break zone and 320m from the eastern reef edge. The depth of the reef flat is quite shallow averaging less than -1m MSL. The island has an elevation ranging from to +1.5m MSL along the island topographic profile survey line. The island could be describes as located on an east west orientation and appears to be growing towards west. Kudahuvadhoo has a natural harbour due the extensive lagoon on the western side of the island. The lagoon extends to about 12km within the reef. The growth of the island towards west has meant that sand is constantly deposited within the deep lagoon creating a steep underwater slope on its western end and allowing vessels to approach close to the shoreline. The island had large areas of undeveloped land allowing the presence of strong vegetation cover on its southern side. Much of this new land is now being developed for Tsunami related resettlement schemes, agriculture, recreation and is predicted to be depleted in the near future. The existing natural environment of the island has been modified, especially in the northern side, although the extent of coastal modifications is small compared to most other inhabited islands. Major modifications include development of a harbour, land reclamation from the excess dredge material during harbour development and clearing of vegetation.

5 2. Natural hazards This section provides the assessment of natural hazard exposure in Feydhoo Island. A severe event history is reconstructed and the main natural hazards are discussed in detail. The final two sections provide the hazard scenarios and hazard zone maps which are used by the other components of this study as a major input. 2.1 Historic events The island of Kudahuvadhoo has been exposed to multiple hazards in the past although its exposure has been limited. A natural hazard event history was reconstructed for the island based on known historical events. As highlighted in methodology section, this was achieved using field interviews and historical records review. Table 2.1 below lists the known events and a summary of their impacts on the island. Table 2.1 Known historic hazard events of Kudahuvadhoo. Metrological Dates of the Impacts hazard recorded events Flooding caused by Heavy rainfall Flooding caused by swells or surges Flooding caused by monsoonal wind waves or Udha Frequent events commonly occurring during SW monsoon. No records of major incidents Annually Flooding limited to a few topographic low areas on the island. The magnitudes and impacts of these floods are small with water levels barely exceeding 0.3m. However, disruptions to socio-economic activities have occurred in the past with schools and shops being closed for over 24 hours. - Impact limited to 10 m from shoreline. In intensity is very low and rarely effects property or human well-being Windstorms 24 June Windstorms are common on the island Dec These events affect housing structures, 1 All dates in italics are adopted from MANIKU, H. A. (1990) Changes in the Topography of Maldives, Male', Forum of Writers on Environment of Maldives. and news paper reports. 2 Unnamed tropical depression passing over Dhaalu atoll between December Source: UNISYS & JTWC (2004) Tropical Cyclone Best Track Data ( ). Accessed 15 April 2005, Unisys Corporation and Joint Typhoon Warning Center.

6 5 other major events since 1980 s (dates unknown). vegetation and crops. The island is generally protected from thick coastal vegetation but even before the settlements expanded, there were reports of windstorm related damages. The effect of wind storm is spread across the entire island. Droughts Earthquake No major event have been reported No major event have been reported Tsunami 26 th Dec 2004 The effect of tsunami 2004 was limited on this island. Flooding occurred on the southern and parts of eastern side. There were no major structures in this area and as a result lost was very little. The flood itself came only about 150m on the southern side and up to a 300m on the eastern side. All these areas were uninhabited. Tsunami floods destroyed a number of agricultural fields, however. One farmer reported a loss of MRF 30,000 worth of crops. The repercussions for the damage were far reaching. He supplied vegetables to a number of islands within the atoll and employs 12 staff seasonally. The staff and the farmer therefore endured loss of income. Apart from the agricultural fields; the only notable damage to the island was to its Harbour. The outer harbour walls collapsed and part of the quay wall was damaged beyond repair. It is still in use but appears unstable. The historic hazardous events for Kudahuvadhoo showed that the island faced the following hazards: 1) windstorms, 2) flooding caused by heavy rainfall, and 3) tsunami. Impacts and frequency of these events vary significantly. Windstorms are the most commonly occurring events followed by flooding due to heavy rainfall. The occurrence of windstorms is usually limited to SW monsoon although occasional localised freak storms due to low pressure systems forming above Maldives effects the island during NE monsoon. It is noteworthy that in spite of the exposure to southern Indian Ocean swell waves, flooding from swell waves or storm surges are almost non-existent in the historical records. The absence of historical records on swell related flood events in

7 nearby islands with similar geographic settings such as Nilandhoo and Magoodhoo, further enhances this finding. The tsunami of 2004 is by far the most significant hazard event in Kudahuvadhoo with substantial economic damage. However, despite its location in a high tsunami hazard zone, the scale of impacts in Kudahuvadhoo is small compared to the other nearby islands such as Vilufushi, Kolhufushi, and Vaanee. The reasons behind the lack of impacts will be explored in latter sections. 2.2 Major hazards Based on the historical records, meteorological records, field assessment and Risk Assessment Report of Maldives (UNDP, 2006) the following meteorological, oceanic and geological hazards have been identified for Kudahuvadhoo. Windstorms Heavy rainfall (flooding) Tsunami Long distance swell waves and local wind waves Earthquakes Climate Change Swell Waves and Wind Waves Long distance swell waves Kudahuvadhoo Island is exposed to effects of swell waves approaching from the Southern Indian Ocean. No site specific wave studies have been undertaken for Kudahuvadhoo but studies undertaken around the country reports a predominantly southwest to a southerly direction for swell waves (Kench et. al (2006), Young (1999), DHI(1999) and Binnie Black & Veatch (2000)). As a result the island is directly in the path of these long distance waves which occasionally reaches abnormal levels capable of flooding (see Figure 2.1).

8 Meemu Atoll Dhaalu Atoll Kudahuvadhoo SW monsoon Wind waves Thaa Atoll NE Monsoon Wind waves Abonormal Abonormal SE SE SE swell swell waves waves SW SW SW Swell Swell Swell Waves Waves Laamu Atoll Estimated wave propogation patterns around Kudahuvadhoo 0 25 kilometers 50 Figure 2.1 Estimated (predominant) wave propagation patterns around Kudahuvadhoo. The shape of the reef and island, and location of the island within the reef system appears to control the flow of wave energy reaching its shoreline (Figure 2.2). Hence, unlike islands located on the western rim of the island (for example G.Dh. Thinadhoo), Kudahuvadhoo enjoys more protection due to its location on the southern rim. Based on an estimation of wave behaviour around Kudahuvadhoo, it is highly likely that waves approach the reef system at an angle and refract along the reef slopes before they dissipate their energy on the reef edge and reef flat. The wider reef flat is also likely to play a major role in energy dissipation before they reach the shoreline. Kench and Brander (2006) reported a relationship between wave energy propagation across a reef flat and, reef width and depth. Using

9 their proposed Reef Energy Window Index, the percentage of occurrence of gravity wave energy on Kudahuvadhoo reef flat is approximately 30%. May 2007 Flood Extent Reef Flat Kudahvadhoo Wave defraction on reef system edge Reduced wave rays on reef flat Wave Refraction and breaking on reef slopes and edge Direction of Swell Waves 0 Wave Crests Figure 2.2 Estimated behaviour of swell waves around Kudahuvadhoo. Udha 500 1,000 meters Flooding is also known to be caused in Kudahuvadhoo by a gravity wave phenomenon known as Udha. These events are common throughout Maldives and especially the southern atolls of Maldives during the SW monsoon. The intensity and impacts of udha waves are usually very low with flooding occurring within 10m of coastline at less than 0.3m height above the ground. It is not expected to be a major hazard in the short-term. The origins of the udha waves as yet remain scientifically untested. No specific research has been published on the phenomenon and has locally been accepted as resulting from local wind waves generated during the onset of southwest monsoon season. The

10 relationship has probably been derived due to the annual occurrence of the events during the months of May or June. It is highly probable that waves originate as swell waves from the Southern Indian Ocean and is further fuelled by the onset of southwest monsoon during May. The timing of these events coincides as May marks the beginning of southern winter and the onset of southwest monsoon. The concurrent existence of these two forms of gravity waves during the southwest monsoon is confirmed by Kench et. al (2006) and DHI(1999). It is also questionable whether the southwest monsoon winds waves alone could cause flooding in islands since the peak tide levels on average are low during May, June and July. Furthermore the strongest mean wind speeds in Male has been observed for November and is more consistent during October to November than during May and June period (Naseer, 2003). This issue needs to be further explored based on long term wave and climatological data of the Indian Ocean before any specific conclusions can be made. However if the relationship does exists, this phenomena could prove to be a major hazard in the face of climate change since the intensity of southern Indian Ocean winter storms is expected to increase. Storm Surges The Disaster Risk Assessment report of 2006 (UNDP, 2006), reported that Kudahuvadhoo was located in a moderate storm surge hazard zone with probable maximum event reaching 0.6m above MSL or 1.53m with a storm tide. The combined historical records of nearby islands in Meemu, Thaa and Laamu Atoll does not show any flooding caused by a storm surge. The occurrence of any abnormal swell waves or surge on Kudahuvadhoo reef flat is dependent on a number of factors such as the wave height, location of the original storm event within the Indian Ocean, tide levels and reef geometry. Future swell event prediction Due to its location, swell related flooding should be considered a serious hazard for Kudahuvadhoo. The island is expected to be exposed to storm waves mainly from south and west south west as shown in the map (Figure 2.3). Events beyond this arch may not influence the island due to the protection offered by Laamu and Thaa Atoll.

11 Possible range of swell wave direction in Dh.Kudahuvadhoo: SE to S Historic storm events Figure 2.3 Historical storm tracks ( ) and possible direction of swell waves for Kudahuvadhoo Island. At present, it is very difficult to forecast the exact probability of swell hazard event and their intensities due to the unpredictability of swell events and lack of research into their impacts on Maldives. Assessment in Kudahuvadhoo is further limited by the lack of historical events. However, since the hazard exposure scenario is critical for this study a tentative exposure scenario has been estimated for the island. There is a probability of major swell events occurring every 20 years with probable water heights above 0.5 m and every 5 years with probable water heights of m. Events with water heights less than 0.2 m are likely to occur annually especially as Udha. The timing of swell events is expected to be predominantly between November and June, based on historic events and storm event patterns (see Table 2.2). Table 2.2 Variation of Severe storm events in South Indian Ocean between 1999 & 2003 (source: (Buckley and Leslie (2004)).

12 Severe wind event variation Longitude band Winter Summer 30 E to 39 E E to 49 E E to 59 E E to 69 E E to 79 E E to 89 E E to 99 E E to 109 E E to 119 E E to 130 E The reclamation plans for Kudahuvadhoo were incomplete at the time of this study. The existing drafts show land reclamation for an airstrip on the southern half of the island. After this development the reef flat width will be reduced to approximately 250m. This reduction in the reef flat width will increase the percentage of occurrence of gravity wave energy on this reef flat to approximately 40% and therefore increasing the probability of flooding caused by surges by 20%. Similarly the impact of flooding will increase relative to encroachment of settlement to coastal areas, even if the probability of flood events remains constant. Potential increase in frequency and intensity of flood events are also probable with climate change and is addressed in a latter section Heavy Rainfall The rainfall pattern in the Maldives is largely controlled by the Indian Ocean monsoons. Generally the NE monsoon is dryer than the SW monsoon. Rainfall data from the three main meteorological stations, HDh Hanimaadhoo, K. Hulhule and S Gan shows an increasing average rainfall from the northern regions to the southern regions of the country (Figure 2.4). The average rainfall at S Gan is approximately 481mm more than that at HDh Hanimadhoo.

13 Mean annual rainfall (mm) Year Gan Hulhule Hanimadhoo Figure 2.4 Map showing the mean annual rainfall across the Maldives archipelago. The closest meteorological station to Kudahuvadhoo is Kadhoo airport which became operational in Unfortunately this study does not have access to Kadhoo data. Moreover, Kadhoo data may be limited for long term trend observation due smaller number of detailed observation years. Hence, to resolve the issue, data from Hulhule has been used. It is recommended that further assessment be made once Kadhoo data becomes available. The mean annual rainfall of Hulhule is mm with a Standard Deviation of 316.4mm and the mean monthly rainfall is 191.6mm. Rainfall varies throughout the year with mean highest rainfall during October, December and May and lowest between February and April (See Figure 2.5).

14 Figure 2.5 Mean Monthly Rainfall in Hulhule ( ). Historic records of rainfall related flooding on the island of Kudahuvadhoo indicates that this island is often flooded and its intensity is high in certain areas. Records for all incidents have not been kept but interviews with locals and research into newspaper reports show that localised levels of flooding within sections of the island. These areas usually correspond to topographic lows within the island. Moreover, substantial topographic variations exist within the island, as is common on larger islands of Maldives. Settlement expansion into and along the edges of these low lying areas have exposed them to flood impact. Heavy rainfall related flooding has been reported to reach up to 0.3 m above the ground level in central areas of the island. The impacts of flooding so far reported has not been disastrous, but has had continued impacts on the community such as disruptions to socio-economic functions such as temporary school and business closures, occasional damage to personal property and crops. It would be possible to identify threshold levels for heavy rainfall for a single day that could cause flooding in Kudahuvadhoo, through observation of historic daily rainfall data. Unfortunately, the nearest weather station, Kadhoo, is 113 km south of the island reducing its applicability to local level analysis. Moreover, we were unable to acquire daily historical data of Kadhoo itself. Available limited severe weather reports shows that Kadhoo received a maximum precipitation of 110.8mm for a 24 hour period on 21 th November 2004 and the island of Meemu Atoll Muli, 82 km NE of Kudahuvadhoo, received a maximum of 193mm on 15 November 2003 (DoM, 2005). Based on interviews with locals, the 2004 event did not have an impact on the island but the 2003 event caused moderate levels of flooding for 2 days. The interviewees were unable to recall a single event with significant impact, suggesting a low intensity of flood events. The probable maximum precipitations predicted for Hulhule and S.Gan by UNDP (2006) are as follows as shown in Table 2.3: Table 2.3 Probable Maximum Precipitation for various Return periods in Hulhule and Gan. Station Return Period 50 year 100 year 200 year 500 year Hulhule Gan

15 Given the high variations in rainfall in Kadhoo, these figures may vary. Based on the field observations and correlations with severe weather reports from Department of Meteorology ((DoM, 2005) the following threshold levels were identified for flooding (Table 2.4). These figures must be revised once historical daily rainfall data becomes available. Table 2.4 Threshold levels for rainfall related flooding in Kudahuvadhoo. Threshold level Impact (daily rainfall) 50mm Puddles on road, flooding in low houses, occasional minor damage to household goods in most vulnerable locations, disruption to businesses and primary school in low areas. 100mm Moderate flooding in low houses; all low lying roads flooded; minor damage to household items, temporary (minor to Moderate) disruptions to socio-economic functions for less than 24 hours 150mm Widespread flooding on roads and low lying areas. Moderate damage to household goods, disruptions to socio-economic functions for more than 24 hours. 200mm Widespread flooding on roads, low areas and houses. Moderate damage to household goods, sewerage network, backyard crops, disruption to socio economic functions for more than 24 hours, gullies created along shoreline, possible damage to road infrastructure. 230+mm Widespread flooding around the island. Major damages to household goods and housing structure, socio economic functions disrupted for more than 48 hours, businesses closed, damage to crops, damage to road infrastructure, sewerage network and quay wall. Quite often heavy rainfall is associated with multiple hazards especially strong winds and possible swell waves. It is therefore likely that a major rainfall event could inflict far more damages those identified in the table Wind storms and cyclones

16 Maldives being located within the equatorial region of the Indian Ocean is generally free from cyclonic activity. There have only been a few cyclonic strength depressions that have tracked through the Maldives, all which occurred in the northern and north central regions. According to the hazard risk assessment report (UNDP, 2006), Kudahuvadhoo falls within the second least hazardous zone for cyclone related hazards and has a maximum predicted cyclonic wind speeds of 56 Kts (see Figure 2.6). There are no such records for the southern region, although a number of gale force winds have been recorded due to low depressions in the region. Winds exceeding 35 knots (gale to strong gale winds) were reported as individual events in Kadhoo weather station annually between 2002 and 2006, all caused by known low pressure systems near Maldives rather than the monsoon (DoM, 2005). The maximum wind speed in Kadhoo during this period was approximately 46 kts. Kulhudhufushi Fonadhoo Thulusdhoo Kudahuvadhoo Thinadhoo Hithadhoo Vilufushi Gan Villingili Feydhoo Hazard Zones probable maximum cyclone wind speed (kts) Figure 2.6 Cyclone hazard zones of the Maldives as defined by UNDP (2006). Interviews with the locals have indicated that the island has been affected by numerous wind storms. Unfortunately records have not been kept for these events, especially their

17 dates or its impacts. However two events have been identified that had moderate impact on the island: June 1987 and December 1992 events. The event of June 1987 affected a number of islands across of Maldives causing damage to crops, vegetation and housing structures. The December 1992 event reached wind speeds over 25 knots and caused moderate damage to crops and vegetation. Damage to properties was mostly caused by falling trees, especially breadfruit trees (Artocarpus altilis). Hence, wind speeds close to near gale winds (see Table 2.5) have caused moderate damage to property and trees on the island. Kudahuvadhoo does have lush vegetation on the southern side dominated by larger trees species, which acts to minimise the direct exposure of properties when winds approach from a south to south westerly direction. Much of this vegetation is now being cleared for development activities, especially for the new stadium and tsunami resettlement housing. In order to perform a probability analysis of strong wind and threshold levels for damage, daily wind data is crucial. However, such data was unavailable for this study. Table 2.5 Beaufort scale and the categorisation of wind speeds. Beau- fort No Description Cyclone category Average wind Average wind speed speed (Knots) (kilometres per hour) Specifications for estimating speed over land 0 Calm Less than 1 less than 1 Calm, smoke rises vertically. 1 Light Air Direction of wind shown by smoke drift, but not by wind vanes. 2 Light breeze Wind felt on face; leaves rustle; ordinary wind vane moved by wind. 3 Gentle breeze Leaves and small twigs in constant motion; wind extends light flag. 4 Moderate breeze Raises dust and loose paper; small branches moved. 5 Fresh breeze Small trees in leaf begin to sway; crested wavelets form on inland waters. 6 Strong breeze Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty. 7 Near gale Whole trees in motion; inconvenience felt when walking against the wind. 8 Gale Category Breaks twigs off trees; generally impedes progress. 9 Strong gale Category Slight structural damage occurs (chimney pots and slates removed). 10 Storm Category Seldom experienced inland; trees uprooted; considerable structural damage occurs. 11 Violent storm Category Very rarely experienced; accompanied by widespread damage. 12 Hurricane Category 3,4,5 64 and over 118 and over Severe and extensive damage. The threshold levels for damage are predicted based on interviews with locals and housing structural assessments provided by risk assessment report (UNDP, 2006), as shown in Table 2.6.

18 Table 2.6 Threshold levels for wind damage based on interviews with locals and available meteorological data. Wind speeds Impact 1-10 knots No Damage knots No Damage knots Light damage to trees and crops knots Breaking branches and minor damage to open crops, some weak roofs damaged knots Minor damage to open crops, minor to moderate damage to vegetation, probability of damage to property due to falling trees knots Minor to Moderate to major damage to houses, crops and trees 40+ Knots Moderate to Major damage to houses, trees falling, crops damaged Tsunami UNDP (2006) reported the region where Kudahuvadhoo is geographically located to be a very high tsunami hazard zone. Kudahuvadhoo Island was considered lucky to escape without substantial damage to properties or infrastructure. This is perhaps due to the fact that other nearby islands such as Kohufushi and Vilufushi were almost completely devastated. Island within Dhaalu Atoll itself, especially the neighbouring Vaanee also experienced extensive damage. According to official reports 20% of the island was flooded. Field surveys and aerial photographs immediately after the event revealed that approximately 30% of the island was flooded. Flooding occurred on the southern and parts of eastern coastline. There were no major structures in this area and as a result impact was minimal. The flood itself came only about m on the southern side and up to a 300 m on the eastern side. All these areas were uninhabited. The main damage occurred to the agricultural fields, however. One farmer reported a loss of MRF 30,000 worth of crops. Apart from the agricultural fields; the only notable damage to the island was to its Harbour. The outer harbour walls collapsed and part of the quay wall was damaged beyond repair. The tsunami run-up height at the eastern shoreline of the island was reported to be approximately 0.8m above MSL reducing to 0.1 m, 300 m inland. Run-up height on the southern shoreline was estimated at 0.9m. It is difficult to identify the local tsunami induced tide level due to the absence of a nearby tide station. Tsunami induced tide level within the lagoon predicted using the tide data from the nearest tide station at

19 Hulhule shows that the island experienced water heights higher than 0.2 above the average northern coastline (Figure 2.7). The small levels of flooding from the northern side, most likely reflects this rise. Figure 2.7 Water level recordings from the tide gauge at Hulhule indicating the wave height of tsunami 2004 (source: University of Hawai i SeaLevel Centre, Comparatively higher exposure of the southern half of Dhaalu Atoll may be partially due to the refraction of the wave caused by the Indian Ocean bathymetry as it travelled westwards Maldives (Ali, 2005). The Indian Ocean bathymetry (Figure 2.8) shows shallower water depths extended far offshore at around the central region of the Maldives (at around the atolls of Laamu Meemu). This shallower area caused the wave to bend away from the southern atolls and became focused towards the central region of the country. It is likely that a similar pattern may persist in any future event if the waves originate from the northern Sundra trench.

20 Fig 2.8 Submarine topography around Maldives archipelago and modelled wave refraction for the December 2004 tsunami (source: Ali (2005)). The predicted probable maximum tsunami wave height for the area where Kudahuvadhoo is located is m (UNDP, 2006). Examination of the flooding that will be caused by a wave run-up of 4.5m for the island of Kudahuvadhoo indicates that such a magnitude wave will flood much of the island. The first m from the shoreline will be a severely destructive zone (Figure 2.9). The theoretical tsunami flood decay curve was plotted for a wave that is applied only for the direct wave from the south eastern oceanward side of the island. It s also is well understood that the tsunami wave will also travel into the atoll lagoon which will cause the water level in the atoll lagoon to rise. This could cause flooding of the island from the lagoonward side of the island, if the water level rises above the height of the island. The maximum tsunami wave induced water level height predicted for the atoll lagoon near Kudahuvadhoo is 1.8m. This could flood the island from the lagoonward side.

21 Height rel MSL (m) Extent of most destructive zone Threshold level of flooding for severe structural damage Distance from oceanward shoreline (m) Figure 2.9 Tsunami related flooding predicted for Kudahuvadhoo based upon theoretical flood decay curve and the maximum probable tsunami wave height at Kudahuvadhoo. Despite the prediction of a m tsunami in Kudahuvadhoo (UNDP, 2006), it is important to note the geophysical settings of Kudahuvadhoo which could make it comparatively less exposed to severe intensity of such events. Characteristics such as island orientation, reef orientation, vegetation cover and presence of multiple coastal ridges could help controlling the intensity and even height of water run-up on the island. Furthermore, the lack of intensity may have been attributed to the lack of development on the south eastern and eastern half of the island. Unlike most islands devastated in the region, Kudahuvadhoo had a 380 m vegetated buffer zone, between the settlement and the coastline. In effect, only a handful of people witnessed flood waters on the southern side while majority of the population witnessed rising waters near the harbour. This tends to suggest the remoteness of the southern areas. With increasing development in the area, especially the tsunami resettlement, an event of similar magnitude will cause more significant damage today Earthquakes

22 There hasn t been any major earthquake related incident recorded in the history of Kudahuvadhoo or even Maldives. However, there have been a number of anecdotally reported tremors around the country. The Disaster Risk Assessment Report (UNDP 2006) highlighted that Thaa Atoll is geographically located in the lowest seismic hazard zone of the entire country. According to the report the rate of decay of peak ground acceleration (PGA) for the zone 1 in which Kudahuvadhoo is located has a value less than 0.04 for a 475 years return period (see Table 2.7). PGA values provided in the report have been converted to Modified Mercalli Intensity (MMI) scale (see column MMI in Table 2.7). The MMI is a measure of the local damage potential of the earthquake. See Table 2.8 for the range of damages for specific MMI values. Limited studies have been performed to determine the correlation between structural damage and ground motion in the region. The conversion used here is based on United States Geological Survey findings. No attempt has been made to individually model the exposure of Kudahuvadhoo Island as time was limited for such a detailed assessment. Instead, the findings of UNDP (2006) were used. Table 2.7 Probable maximum PGA values in each seismic hazard zone of Maldives (modified from UNDP, 2006). Seismic PGA values for MMI 3 hazard zone 475yrs return period 1 < 0.04 I I I I-II II-III Table 2.8 Modified Mercalli Intensity description (Richter, 1958). MMI Shaking Description of Damage Value Severity I Low Not felt. Marginal and long period effects of large earthquakes. II Low Felt by persons at rest, on upper floors, or favourably placed. III Low Felt indoors. Hanging objects swing. Vibration like passing of light trucks. Duration estimated. May not be recognized as an earthquake. IV Low Hanging objects swing. Vibration like passing of heavy trucks; or sensation of a jolt like a heavy ball striking the walls. Standing motor cars rock. Windows, dishes, doors rattle. Glasses clink. Crockery clashes. In the 3 Based on KATZFEY, J. J. & MCINNES, K. L. (1996) GCM simulation of eastern Australian cutoff lows. Journal of Climate,

23 upper range of IV, wooden walls and frame creak. V Low Felt outdoors; direction estimated. Sleepers wakened. Liquids disturbed, some spilled. Small unstable objects displaced or upset. Doors swing, close, open. Shutters, pictures move. Pendulum clocks stop, start, change rate. VI-XII Light - Catastrophe Light to total destruction According to these findings it is unlikely that Kudahuvadhoo will receive an earthquake capable of causing destruction. It should however be noted that the actual damage may be different in Maldives since the masonry and structural stability factors have not been considered at local level for the MMI values presented here. Usually such adjustments can only be accurately made using historical events, which is almost nonexistent in Maldives Climate Change The debate on climate change, especially Sea Level Rise (SLR) is far from complete. Questions have been raised about SLR itself (Morner et al., 2004, Morner, 2004) and the potential for coral island environments to naturally adapt (Kench et al., 2005, Woodroffe, 1993). However the majority view of the scientific community is that climate is changing and that these changes are more likely to have far reaching consequences for Maldives. For a country like Maldives, who are most at risk from any climate change impacts, it is important to consider a cautious approach in planning by considering worst case scenarios. The findings presented in this section are based on existing literature. No attempt has been made to undertake detailed modelling of climate change impacts specifically on the island due to time limitations. Hence, the projection could change with new findings and should be constantly reviewed. The most critical driver for future hazard exposure in Maldives is the predicted sea level rise and Sea Surface Temperature (SST) rise. Khan et al. (2002, Woodroffe, 1993) analysis of tidal data for Gan, Addu Atoll shows the overall trend of Mean Tidal Level (MTL) is increasing in the southern atolls of Maldives. Their analysis shows an increasing annual MTL at Gan of 3.9 mm/year. These findings have also been backed by a slightly higher increase reported for Diego Garcia south of Addu Atoll (Sheppard, 2002). These calculations are higher than the average annual rate of 5.0 mm forecasted

24 by IPCC (2001), but IPCC does predict a likely acceleration as time passes. Hence, this indicates that the MTL at Gan by 2100 will be nearly 0.4m above the present day MTL. Similarly, Khan et al. (2002) reported air temperature at Addu Atoll is expected to rise at a rate of 0.4C per year, while the rate of rise in SST is 0.3C. Although no specific studies have been done for Thaa Atoll, the findings from Addu Atoll could be used as a guide to predicted changes. Predicted changes in extreme wind gusts related to climate change assumes that maximum wind gusts will increase by 2.5, 5 and 10 per cent per degree of global warming (Hay, 2006). Application of the rate of rise of SST to the best case assumption indicates a 15% increase in the maximum wind gusts by the year 2010 in southern Atolls. The global circulation models predict an enhanced hydrological cycle and an increase in the mean rainfall over most of the Asia. It is therefore evident that the probability of occurrence and intensity of rainfall related flood hazards for the island of Gan will be increased in the future. It has also been reported that a warmer future climate as predicted by the climate change scenarios will cause a greater variability in the Indian monsoon, thus increasing the chances of extreme dry and wet monsoon seasons (Giorgi and Francisco, 2000). Global circulation models have predicted average precipitation in tropical south Asia, where the Maldives archipelago lies, to increase at a rate of 0.14% per year (Figure 2.10). Increase of precipitation (%) Rate of increase = 0.135% per year Year

25 Figure 2.10 Graph showing the rate of increase of averaged annual mean precipitation in tropical south Asia (Adger et al., 2004). There are no conclusive agreements over the increase in frequency and intensity of Southern Indian Ocean Storms. However, some researchers have reported a possible increase in intensity and even a northward migration of the southern hemisphere storm belt (Kitoh et al., 1997) due rise in Sea Surface Temperatures (SST) and Sea Level Rise. If this is to happen in the Southern Indian Ocean, the frequency of and intensity of storms reaching Kudahuvadhoo Island coastline will increase and thereby exposing the island more frequent damages from swell waves. The increase in sea level rise will also cause the storms to be more intense with higher flood heights. The above discussed predicted climate changes for Kudahuvadhoo and surrounding region is summarised in Table 2.9. It should be cautioned that the values are estimates based on most recent available literature on Maldives which themselves have a number of uncertainties and possible errors. Hence, the values should only be taken as guide as it existed in 2006 and should be constantly reviewed. The first three elements are based climate change drivers while the bottom three is climatological consequences. Table 2.9 Summary of climate change related parameters for various hazards. Element Predicted Predicted change (overall rise) Possible impacts on rate of Hazards in Gan Best Case Worst Case change SLR mm /yr Yr 2050: +0.2m Yr 2100: +0.4m Yr 2050: +0.4m Yr 2100: +0.88m Tidal flooding, increase in swell wave flooding, reef drowning Air Temp 0.4 C / decade Yr 2050: Yr 2100: SST 0.3 C / decade Yr 2050: Yr 2100: Increase in storm surges and swell wave related flooding, Coral bleaching & reduction in coral defences Rainfall +0.14% / yr (or +32mm/yr) Yr 2050: +1384mm Yr 2100: Increased flooding, Could effect coral reef growth

26 +2993mm Wind gusts 5% and 10% / degree of warming Yr 2050: +3.8 Knots Yr 2100: +8.3 Knots Yr 2050: +7.7Knots Yr 2100: Knots Increased windstorms, Increase in swell wave related flooding. Swell Waves Frequency expected to change. Increase in swell wave related flooding. Wave height in reef expected to be high 3.3 Event Scenarios Based on the discussion provided in section 2.2 above, the following event scenarios have been estimated for Kudahuvadhoo Island (Tables 2.10, 2.11, and 2.12). Table 2.10 Rapid onset flooding hazards Hazard Max Prediction Impact thresholds Probability of Occurrence Swell Waves (wave heights on reef flat Average Island ridge height +1.9m above reef flat) Tsunami (wave heights on reef flat) SW monsoon high seas Heavy Rainfall (For a 24 hour period) Low Moderat e Sever e Low Impact Moderate Impact Severe Impact NA < 2.3m > 2.3m > 3.0m High Moderate Low 3.7m < 2.3m > 2.3m > 3.0m Modera te 1.5m < 2.3m mm <60m m Low Very low > 2.3m > 3.0m High Very low Unlikely > 60mm >175m m High Moderate Low

27 Table 2.11 Slow onset flooding hazards (medium term scenario year 2050). Hazard Impact thresholds Probability of Occurrence Low Moderate Severe Low Moderate Severe SLR: Flooding SLR: Waves Tidal Swell < 2.3m > 2.3m > 3.0m Moderate Very Low Very Low < 2.3m > 2.3m > 3.0m Very high Moderate Low SLR: Rainfall Heavy <60mm >60mm >175mm Very High Table 2.12 Other rapid onset events. Hazard Max Impact thresholds Prediction Moderate Low Probability of Occurrence Low Moderate Severe Low Moderate Severe Wind storm NA <30 knts Earthquake (MMI value 4 ) > 30 knts > 45Knts Very High I < IV > IV > VI Very Low High Unlikely Moderate none 2.4 Hazard zones Hazard zones have been developed using a hazard intensity index. The index is based on a number of variables, namely historical records, topography, reef geomorphology, vegetation characteristics, existing mitigation measures (such as breakwaters) and hazard impact threshold levels. The index ranges from 0 to 5 where 0 is considered as no impact and 5 is considered as very severe. In order to standardise the hazard zone for use in other components of this study only events above the severe threshold were considered. Hence, the hazard zones should be interpreted with reference to the hazard scenarios identified above Swell waves and SW monsoon high Waves The intensity of swell waves and SW monsoon udha is predicted to be highest 50m from the coastline on the ocean ward side (see Figure 2.11) and 30 m from the lagoonward side. Swell waves higher than 3.0 m on reef flat are predicted to penetrate inner island 4 Refer to earthquake section above

28 up to or beyond 200m from the coastline. The longest run-up would be from the oceanward coastline where it could penetrate 250 m inland. The run-up on the island is controlled by topography as the flood waters decay below 0.4 m. The presence of multiple ridges on the oceanward side helps prevent flood run-up beyond 250 m. The lagoonward side is relatively safe form swell related flooding due to the protection provided by the atoll rim. However, waves could refract around the reef system and the island causing flooding close to the shoreline. Such impacts are predicted to be limited to m from the lagoonward coastline and their intensity is expected to remain low. SW monsoon high waves (udha) are not expected to have an impact beyond 50m of the coastline and are more likely to influence the coastline right around the island. Hazrad Zoning Map Swell Waves, Udha & Storm Surges Intensity Index Low High Contour lines represent intensity index based on a severe event scenarios metres Figure 2.11 Hazard zoning map for swell wave, storm surges and southwest monsoon high seas Tsunamis

29 When a severe threshold of tsunami hazard (>3.0 m on reef flat) is considered, 70% of the island is expected to be directly affected (Figure 2.12). If the waves reach beyond 4.0 m MSL 90% of the island is likely to be flooded due the prevalent tide levels. High intensity waves will flush through the island from the eastern and southern side while tide related surges will occur within the atoll, flooding the northern coastline. The intensity of flood waters will be highest m from the shoreline. The water run-up is expected to be controlled on the southern and south eastern side by the presence of second relic ridge 250 m from the coastline. Similar high areas exist around the island which could control the flood waters as the wave decays. Wave height around the island will vary based on the original tsunami wave height, but the areas marked as low intensity is predicted to have proportionally lower heights compared to the coastline. Hazrad Zoning Map Tsunami Intensity Index Low Contour lines represent intensity index based on a severe event scenario (wave heights +3.0m MSL) High metres 300

30 Figure 2.12 Hazard zoning map for tsunami flooding Heavy Rainfall Heavy rainfall above the severe threshold is expected to flood parts of the settlement (Figure 2.14). The areas predicted for severe intensity are the topographic lows in the southern and central parts of the island. These areas act as drainage basins for the surrounding higher areas and due the large size of the island the catchments area is considerable for surface runoff during heavy rainfall. The intensity is generally expected to be low in most locations. The hazard zone presented in the map below is based on the topographic surveys done on the island. Due to the large size of the island it was impossible to assess the topographic variation across the entire island during this project. Hence the hazard zones shown below should be considered as the most prominent zones only. More detailed assessment is required once high resolution topographic data becomes available. Hazrad Zoning Map Heavy Rainfall Intensity Index Low High Contour lines represent intensity index based on a severe event scenario (+175mm in 24 hours) Note: White areas represent areas with no data metres 300 Figure 2.14 Hazard zoning map for heavy rainfall related flooding.

31 2.4.4 Strong Wind The intensity of the strong wind across the island is expected to remain fairly constant. Smaller variations may exist between the west and east side where by the west side receives higher intensity due to the predominant westerly direction of abnormally strong winds. The entire island has been assigned an intensity index of 4 for strong winds during a severe event Earthquakes The entire island is a hazard zone with equal intensity. An intensity index of 1 has been assigned Climate Change Establishing hazard zones specifically for climate change is impractical at this stage due to the lack of topographic and bathymetric data. However, the predicted impact patterns and hazard zones described above are expected to be prevalent with climate change as well, although the intensity is likely to slightly increase Composite Hazard Zones A composite hazard zone map was produced using a GIS based on the above hazard zoning and intensity index (Figure 2.15). The coastal zone approximately 200m from the oceanward coastline and the topographically low areas within the island are predicted to be the most intense regions for multiple hazards. The eastern side is particularly identified as a hazard zone due to the exposure to swell waves, storm surges, udha and tsunamis. The overall composite increase in intensity for hazard zones have resulted from high exposure to intense windstorms across the island.

32 Hazard Zoning Map Multiple Hazards Intensity Index Low Contour lines represent intensity index based on severe event scenarios High metres 300 Figure 2.15 Composite hazard zone map.

33 2.5 Limitations and recommendation for future study The main limitation for this study is the incompleteness of the historic data for different hazardous events. The island authorities do not collect and record the impacts and dates of these events in a systematic manner. There is no systematic and consistent format for keeping the records. In addition to the lack of complete historic records there is no monitoring of coastal and environmental changes caused by anthropogenic activities such as road maintenance, beach replenishment, causeway building and reclamation works. It was noted that the island offices do not have the technical capacity to carryout such monitoring and record keeping exercises. It is therefore evident that there is an urgent need to increase the capacity of the island offices to collect and maintain records of hazardous events in a systematic manner. The second major limitation was the inaccessibility to long-term meteorological data from the region. Historical meteorological datasets atleast as daily records are critical in predicting trends and calculating the return periods of events specific to the site. The inaccessibility was caused by lack of resources to access them after the Department of Meteorology levied a substantial charge for acquiring the data. The lack of data has been compensated by borrowing data from alternate internet based resources such as University of Hawaii Tidal data. A more comprehensive assessment is thus recommended especially for wind storms and heavy rainfall once high resolution meteorological data is available. The future development plans for the island are not finalised. Furthermore the existing drafts do not have proper documentations explaining the rationale and design criteria s and prevailing environmental factors based on which the plan should have been drawn up. It was hence, impractical to access the future hazard exposure of the island based on a draft concept plan. It is recommended that this study be extended to include the impacts of new developments, especially land reclamations, once the plans are finalised. The meteorological records in Maldives are based on 5 major stations and not at atoll level or island level. Hence all hazard predictions for Gan are based on regional data rather than localised data. Often the datasets available are short for accurate long term prediction. Hence, it should be noted that there would be a high degree of estimation and the actual hazard events could vary from what is described in this report. However, the findings are the closest approximation possible based on available data and time,

34 and does represent a detailed although not a comprehensive picture of hazard exposure in Gan.

35 References ALI, S. (2005) December Tsunami Impact Assessment and a Tsunami Risk Assessment of the Maldives. School of Civil Engineering and the Envrionment. Southampton, United Kingdom, University of Southampton,. BINNIE BLACK & VEATCH (2000) Enviromental / Technical study for dredging / reclamation works under Hulhumale' Project - Final Report. Male', Ministry of Construction and Public Works. BUCKLEY, B. W. & LESLIE, L. M. (2004) Preliminary climatology and improved modelling of South Indian Ocean and southern ocean mid-latitude cyclones. International Journal of Climatology, 24, DEPARTMENT OF METEOROLOGY (DOM) (2005) Severe weather events in and Accessed 1 November 2005, < Department of Meteorology, Male', Maldives. DHI (1999) Physical modelling on wave disturbance and breakwater stability, Fuvahmulah Port Project. Denmark, Port Consult. GIORGI, F. & FRANCISCO, R. (2000) Uncertainties in regional climate change prediction: a regional analysis of ensemble simulations with HadCM2 coupled AOGCM. Climate Dynamics, 16, HAY, J. E. (2006) Climate Risk Profile for the Maldives. Male', Ministry of Envrionment Energy and Water, Maldives. IPCC (2001) Climate Change 2001: The Scientific Basis, New York, Cambridge, United Kingdom and New York, NY, USA. KATZFEY, J. J. & MCINNES, K. L. (1996) GCM simulation of eastern Australian cutoff lows. Journal of Climate, KENCH, P. S. & BRANDER, R. W. (2006) Wave processes on coral reef flats: Implications for Geomorphology using Australian Case Studies. Journal of Coastal Research, 22, KENCH, P. S., MCLEAN, R. F. & NICHOL, S. L. (2005) New model of reef-island evolution: Maldives, Indian Ocean. Geology, 33, KHAN, T. M. A., QUADIR, D. A., MURTY, T. S., KABIR, A., AKTAR, F. & SARKAR, M. A. (2002) Relative Sea Level Changes in Maldives and Vulnerability of Land Due to abnormal Coastal Inundation. Marine Geodesy, 25, KITOH, A., YUKIMOTO, S., NODA, A. & MOTOI, T. (1997) Simulated changes in the Asian summer monsoon at times of increased atmospheric CO2. Journal of Meteorological Society of Japan, 75, MANIKU, H. A. (1990) Changes in the Topography of Maldives, Male', Forum of Writers on Environment of Maldives. MORNER, N.-A. (2004) The Maldives project: a future free from sea-level flooding. Contemporary South Asia, 13, MORNER, N.-A., TOOLEY, M. & POSSNERT, G. (2004) New perspectives for the future of the Maldives. Global and Planetary Change, 40,

36 NASEER, A. (2003) The integrated growth response of coral reefs to environmental forcing: morphometric analysis of coral reefs of the Maldives. Halifax, Nova Scotia, Dalhousie University. RICHTER, C. F. (1958) Elementary Seismology, San Francisco, W.H. Freeman and Company. SHEPPARD, C. R. C. (2002) Island Elevations, Reef Condition and Sea Level Rise in Atolls of Chagos, British Indian Ocean Territory. IN LINDEN, O., D. SOUTER, D. WILHELMSSON, AND D. OBURA (Ed.) Coral degradation in the Indian Ocean: Status Report Kalmar, Sweden, CORDIO, Department of Biology and Environmental Science, University of Kalmar. UNISYS & JTWC (2004) Tropical Cyclone Best Track Data ( ). Accessed 15 April 2005, Unisys Corporation and Joint Typhoon Warning Center. WOODROFFE, C. D. (1993) Morphology and evolution of reef islands in the Maldives. Proceedings of the 7th International Coral Reef Symposium, Guam, University of Guam Marine Laboratory. YOUNG, I. R. (1999) Seasonal variability of the global ocean wind and wave climate. International Journal of Climatology, 19,

37 3. Environment Vulnerabilities and Impacts 3.1 Environment Settings Terrestrial Environment Topography The topography of Kudahuvadhoo was assessed using three topographic profiles (see Figure 3.1). Given below are the general findings from this assessment N Topographic Profiles Location of w ells P3 Profile Number N P3 P N P1 Topographic Survey Locations E E metres 300 Figure 3.1 Topography field survey locations The island is generally low lying with an average elevation of m MSL along the surveyed island profiles. This finding was reconfirmed from the shallow depths of ground water table around the island (on average approximately 1 m at median tide). As characteristic of large islands, considerable variations in topography were observed in Kudahuvadhoo.

38 The main topographic features along Profile 1 (P1) are the coastal ridge on the oceanward side (+1.5 m), a 75m wide low area (+0.45m) and higher ridge like feature approximately 300 m from coastline (see Figure 3.2). The settlement area is generally low at about +0.8 m MSL. The high ridge like feature may perhaps represent an old shoreline during the evolution of the island. The adjacent low area and the present ridge system are reminiscent of an island undergoing a long period of accretion and subsequent stabilisation. The area nonetheless appears to be a major natural asset of the island against flooding events due to the double ridge and low drainage zone. The low areas were reported to be regular flood zone during heavy rainfall. At present no developments have been made in the area, except agricultural plots, which appears to be thriving in the area. Future housing developments have been planned within the low area and may have implications during major flooding events. These issues will be discussed in a latter section. Low areas were identified in the existing settlements which corresponded with reported rainfall related flood zone. Most notable of these were the areas around the Atoll Education Centre and Pre-school. G G Profile P1 Harbour Quay Wall Extent of reclaimed land Extent of Existing Settlement High point (+1.2m) Possibly and old ridge Low Area (+0.475) Oceanward Ridge (+1.5m) G G 1m Existing settlement 0 Approximate Mean Sea Level Lagoonward Side Oceanward Side * o No clear sight. Deviation of 5. The length does not reflect the island width but accurately represents depth variations * 900 Figure 3.2 Topographic profile P1. The main topographic features along Profile 2 (P2) are the consistent low elevation (less than 1.0 m MSL and the presence of a ridge like feature approximately 250 m inland (see figure 3.3). This high area could be part of the old ridge system described above for

39 P1since it has a similar heights and distance from coastline. It may be possible that this ridge extends around the south and east sides of the island. The oceanward ridge along the survey line has been considerably cleared and modified during the construction of a waste management centre. Hence, the height of 1.3m may not represent the actual ridge height. However, observations of coastline further south and north of the area showed no significant changes in height. If ridge height is a crude indicator of wave power, the area is considerably less exposed to strong wave action compared to the coastline facing the southern reef edge. In general the coastline topography and geomorphology around the island is reminiscent of islands in low energy settings around Maldives. Hence, it is very likely that Kudahuvadhoo has low exposure to strong wave action. Some possible reasons for lack of exposure include island location within the reef, atoll and the archipelago, which on initial observation appears to protect the island from high energy events and seasonal wave action. Relatively young Low area (+0.5m) G G Profile P2 New Settlement Low area (+0.8m) High Point (+1.2m) Low area (+0.8m) Oceanward Ridge (+1.3m) Area modified for waste site construction G G 1m 0 Lagoonward Side Approximate Mean Sea Level Oceanward Side Figure 3.3 Topographic Profile P2. Based on the topographic profiles, a crude estimate of the island topography was developed. Figure 3.4 shows the predicted main high and low areas of the island.

40 High areas Low areas Topographic Survey Locations metres Figure 3.4 Predicted high and low areas of Kudahuvadhoo. Vegetation Despite being a large island, the vegetation of Kudahuvadhoo is rapidly being depleted. At present 50% of the island comprises of moderate to dense vegetation. However, approximately half of the vegetated area is currently being utilised for agriculture and various human activities. Hence, much of the vegetation cover is low and the amount of dense vegetation cover is limited to 20% (see Figure 3.5). Much of the undeveloped areas on the southern half of the island have been cleared for agricultural activities. New housing developments in the areas have also resulted in vegetation cover to be reduced. The coastal vegetation on the island is dense but narrow in most locations, especially along the southern coastline. This has been a result of agricultural plots encroaching coastal vegetation. Coastal erosion has further narrowed the vegetation strip in the southern coastline. There is a strong presence of vegetation in both the southeast and

41 southwest corner of the island, crucial for keeping the erosion prone areas stable. The planned new developments would remove much of this vegetation, however. Major vegetation patches Agricultural land and recreational areas Settlement in 2004 Reclaimed land Current Tsunami housing project Planned expansion of settlement Vegetation Distribution metres 300 Figure 3.5 Distribution of Vegetation. Ground Water and Soil Kudahuvadhoo is expected to have a substantial layer of fresh water. Water lens depth varies across the island based on topography. Generally the water table could be reached with less than 1m at median tide. This could decrease to 0.5m during spring high tides or more during heavy rainfall. There are no areas above water table or wetland areas within Kudahuvadhoo. Kudahuvadhoo s ground water was reported to be in generally in good quality (MPND, 2005). The inhabitants reported no shortages of drinking water in the past due to the good quality of ground water. However, the settlement were reported be experiencing gradual decline in quality due to contamination and over extraction. The Friday Mosque,

42 located away for the settlement is still used as a source of ground water during periods of low rainfall. Rainwater is the main source of drinking water in 2004 (MPND, 2005). The soil conditions varied from north to south. The main observation was that the southern half of the island had a large humus layer while the northern parts had comparatively small humus layer. This finding may generally be explained by the presence of settlement in the north and agricultural or undeveloped land in the south Coastal Environment Beach and Beach Erosion Kudahuvadhoo island beach environment has remained relatively stable over the past 45 years. Currently the islands western and southern shorelines are very active while the northern and eastern shorelines have undergone a reduction in mobility due to coastal developments. The western shoreline appears to be growing despite the coastal development in the north. This may be related to the constant sediment supply from the south, especially during the northeast monsoon, which is considered the most dominant supply route. It is also highly likely that the major island building processes takes place during northeast monsoon. Beach rock was found along an 800m stretch of the southern shoreline (see Figure 3.6). Part of the beachrock was covered with accretion, indicating seasonal variation in beachrock exposure. The beachrock areas were located 2-5m away from the present shoreline further indicating the seasonal nature of erosion. There are areas of accretion on the west and east sides and areas of erosion on north, south and east sides. Erosion on north side may not cease in the short-term, as it could be related to the stabilisation process after land reclamation. The islanders did not identify erosion as a major problem.

43 Accretion Erosion Exposed Beach Rock 1969 Vegetation Line 1969 Beach Line 2004 Island Area 2000 New ly Reclaimed Land Figure 3.6 Erosion and accretion in Kudahuvadhoo Marine environment General Reef Conditions General historical changes to reef conditions were assessed anecdotally, though interviews with a number of fishermen and young snorkelers. The general agreement amongst the interviewees were that the quality of reef areas on the southern reef line had declined considerably over the past 50 years with a lowering of coral cover and reduction in fish numbers. Reef conditions on the northern reef line were reported to be in relatively good condition as is the areas of the reef away from Kudahuvadhoo. Patches of seagrass can be found on the eastern and southern side of the island and could soon spread to the western side of the island. Overgrowth of seagrass may become a major nuisance in the future due to the low currents observed in the region.

44 3.1.4 Modifications to Natural Environment Coastal Modifications Piled Jetty Land Reclamation Harbour and entrance dredging Piled Jetty Breakwaters Dredged area (boat landing area) Coastal Developments metres 300 Figure 3.7 Coastal modifications in Kudahuvadhoo. As in most inhabited islands of Maldives, access infrastructure has been developed in Kudahuvadhoo Island. These include a harbour, harbour entrance channel, breakwaters, dredged areas for boat landing and land reclamation as a method of dredge material disposal. Two piled jetties were also developed on the western side of the island prior to the development of harbour. Almost all the development activities have been located in the northern half of the island. No coastal developments were undertaken on the southern side of the island As a result of these modifications, coastal processes in the northern part of the island appear to have altered considerably.

45 Terrestrial Modifications As presented earlier, substantial changes to the vegetation was necessitated due to the expanding human settlement. Vegetation cover comprising larger trees have been reduced by almost 50% within the last 45 years and are predicted to decline further due to the planned settlement expansion and lack of re-vegetation policies. Coastal vegetation has been considerably reduced over the past 10 years and may continue to do so with the planned expansion. The modification to topography, especially from road maintenance activities is minimal. Parts of the eastern coastline have had considerable modifications along the ridge areas close to shoreline due to past and current waste management activities. Saltwater intrusion in the water lens was not reported as an issue on the island. 3.2 Environmental mitigation against historical hazard events Natural Adaptation There is little evidence that Kudahuvadhoo was in the past exposed to severe storm events or intense wave activity. The presence of multiple ridges on the southern part of the island does indicate abrupt changes to coastline in response to changing wave conditions, however. The height of these ridges is quite low and material quite fine, indicating a possible lack of intense storm activity or strong wave action. It is apparent from Kudahuvadhoo s observation that the island adapts to the limited long-term hazards it experiences and mitigates them naturally but is still exposed to infrequent high impact hazards. In this sense the southern coastline is critical zone for future natural adaptation of the island Human Adaptation Kudahuvadhoo has no major mitigation measures undertaken to prevent exposure to natural hazards. The main activities include construction of breakwaters to protect the harbour and the use of coastal protection measures to prevent erosion in the reclaimed area. Additionally some roads works have been undertaken in the past to mitigate rainfall related flooding, but there is no continuous road maintenance programme. The

46 lack of both natural and human adaptation measures could be taken as crude indicator of the historical exposure of the island to natural hazards, specifically climate related hazards. 3.3 Environmental vulnerabilities to natural hazards Natural Vulnerabilities Island is generally low lying and therefore exposed to flooding from the southern and north eastern side of the island. Topographic variations within the island exposes certain areas to heavy rainfall associated flooding and creates condition for flood run-up during ocean induced flooding events. Currently the low areas experience heavy rainfall related flooding almost regularly, effecting island functions such as schools and economic activities. There are major low areas in the present uninhabited areas of the island and could become a major issue due to settlement expansion. Analysis of flood extents during tsunami shows that the effects of topographic lows were prominent in the wave run up. The ridges around the island and more importantly on the southern side are not high enough to prevent the or +2.30m storm surges predicted in the hazard scenarios. Its location facing the Veymandoo Channel and bathymetric features off the eastern coastline of Maldives exposes the island to effects of tsunamis Human induced vulnerabilities The lack of coastal vegetation in certain parts of the coastline is a major concern in terms of exposure to natural hazards. Coastal vegetation including the undergrowth acts as natural barrier against tsunami s, other ocean induced flooding events and wind storms. A wider coastal vegetation belt would absorb wave energy from a tsunami or a flooding event reducing the impact on infrastructure and human settlement. This has been proven from findings across the nine islands studied under this project. In Kudahuvadhoo Island itself, coastal vegetation is predicted to have played a major role in preventing the wave run-up on land due to the vegetation belt and agricultural crops. Stronger coastal

47 vegetation also reduces wind energy during wind storms and protects settlement areas near the coastline. Coastal vegetation also plays a critical role in stabilising the beach areas and assists in controlling erosion. Hence consistent decline in coastal vegetation along the southern and western shoreline exposes these areas to above mentioned hazards. Similar to the lack of coastal vegetation, the removal of vegetation from the settlement area exposes the structures to the direct effects of strong wind. The effects of climate change and global warming could be felt more strongly due to the apparent increase in temperature within the settlement area. The northern coastline of the island has been modified to develop a harbour. Since its development, it was observed that considerable erosion was experienced by the newly reclaimed land, probably in search of equilibrium in coastal processes of the region. It was also observed that the southern half of the island remains more exposed during both monsoons. Developments in northern coastline would have implications for the stability of southern coastline if enough sediment is not transported to the southern side during SW monsoon. It may be a long time before the coastline adapts to the new modifications, by which time it is highly likely that mitigation measures for coastal erosion will be put in place, further changing the coastal processes. Reefs form the first line of defence in coral islands against waves and predicted sea level rise. A functioning and healthy reef is essential for a number of geomorphologic functions such as sediment production and reef adaptation to rising sea levels. The natural history of Maldives bears evidence of the role reefs played in natural adaptation to varying sea levels. The fact that the southern side of the reef of Kudahuvadhoo is in good condition is an asset. However, the past inappropriate human activities in the reef such as coral mining and the gradual decline of reef condition on the eastern and northern ends probably would increase the sea level rise hazard in Kudahuvadhoo. 3.4 Environmental assets to hazard mitigation The relatively large size of Kudahuvadhoo is its main asset against natural hazards. During ocean induced flooding events, the extent of impact on the settlement may be considerably reduced due the limited extent of inundation, as

48 has been demonstrated by the tsunami of 2004 and other flooding events (see Natural Hazards Section). The location of the island on the western line of atolls and on the southern end of Dhaalu Atoll has meant that the island is relatively less exposed to major ocean induced hazards. It is relatively protected from the long distant swell waves coming from the east and the monsoon driven waves coming from the west. Evidence from the ridge heights also shows that the island has not been exposed to strong wave action or storm activity in the past. Location within the archipelago has also meant that Kudahuvadhoo is less exposed to storm surges and strong winds. However, the island is exposed to tsunami due to the ocean topography off the eastern rim of Maldives towards Kudahuvadhoo (Shifaz, 2004). The east-west orientation of the island can generally be regarded as an asset in terms of exposure to ocean induced hazards and strong wind related hazards. It has been found that islands on an east west orientation experienced far less impacts during the tsunami of 2004 and in previous flooding events. Strong coastal vegetation along the majority of the island s coastline act as a strong defence line against ocean induced floods and strong winds. The present agricultural land acts as a buffer between the settlement and oceanward coastline, protecting the settlement from sea induced floods. The protection however comes at an expense to the agricultural crops. The tsunami of 2004 failed to affect the settlement area due the presence of this wide vegetation belt, but also destroyed much of the agricultural crops. Kudahuvadhoo appears to have two major routes for sediment supply due to its location on the reef system. This has allowed the island to grow westward consistently in spite of the presence of a deep lagoon. This also has probably meant a reduced but a consistent supply of sediments from the southern route (see existing environment section) even after the construction of the harbour. More detailed studies are required to confirm this finding. Kudahuvadhoo Island s coastal environment has remained predominantly stable over the past 50 years (based on historical information and field evidence). Perhaps this stability is largely due to a consistent sediment supply and due the location of the island within the archipelago and reef system. Changes after the

49 construction of the harbour have not been monitored well, but thus far does not seem to have led to major net erosion in the original island. The topographic lows on the southern half of the island may act as a drain during flooding events, preventing wave run-up further inland. Reef width appears to play an important role increasing or decreasing the impacts of ocean induced wave activity. The impact of gravity waves such as tsunami s for example has its impacts reduced based on the length of reef. As has been discussed in the natural hazards chapter, these findings are preliminary and needs further inquiry using detailed empirical research. 3.5 Predicted environmental impacts from natural hazards The natural environment of Kudahuvadhoo and islands in Maldives archipelago in general appear to be resilient to most natural hazards. The impacts on island environments from major hazard events are usually short-term and insignificant in terms of the natural or geological timeframe. Natural timeframes are measured in 100 s of years which provides ample time for an island to recover from major events such as tsunamis. The recovery of island environments, especially vegetation, ground water and geomorphologic features in tsunami effected islands like Laamu Gan provides evidence of such rapid recovery. Different aspects of the natural environment may differ in their recovery. Impacts on marine environment and coastal processes may take longer to recover as their natural development processes are slow. In comparison, impacts on terrestrial environment, such as vegetation and groundwater may be more rapid. However, the speed of recovery of all these aspects will be dependent on the prevailing climatic conditions. The resilience of coral islands to impacts from long-term events, especially predicted sea level rise is more difficult to predict. On the one hand it is generally argued that the outlook for low lying coral island is catastrophic under the predicted worst case scenarios of sea level rise (IPCC 1990; IPCC 2001), with the entire Maldives predicted to disappear in years. On the other hand new research in Maldives suggests that contrary to most established commentaries on the precarious nature of atoll islands Maldivian islands have existed for 5000 yr, are morphologically resilient rather than fragile systems, and are expected to persist under current scenarios of future climate change and sea-level rise (Kench, McLean et al. 2005). A number of prominent

50 scientists have similar views to the latter (for example, Woodroffe (1993), Morner (1994)). In this respect, it is plausible that Kudahuvadhoo may continue to naturally adapt to rising sea level. There are two scenarios for geological impacts on Kudahuvadhoo. First, if the sea level continues to rise as projected and the coral reef system keep up with the rising sea level and survive the rise in Sea Surface Temperatures, then the negative geological impacts are expected to be negligible, based on the natural history of Maldives (based on findings by Kench et. al (2005), Woodroffe (1993)). Second, if the sea level continues to rise as projected and the coral reefs fail to keep-up, then their could be substantial changes to the land and beaches of Kudahuvadhoo (based on (Yamano 2000)). The question whether the coral islands could adjust to the latter scenario may not be answered convincingly based on current research. However, it is clear that the highly, environments of Kudahuvadhoo, especially the northern coastline, stands to undergo substantial change or damage (even during the potential long term geological adjustments), due to potential loss of land through erosion, increased inundations, and salt water intrusion into water lens (based on Pernetta and Sestini (1989), Woodroffe (1989), Kench and Cowell (2002)). As noted earlier, environmental impacts from natural hazards will be apparent in the short-term and will appear as a major problem in inhabited islands due to a mismatch in assessment timeframes for natural and socio-economic impacts. The following table presents the short-term impacts from hazard event scenarios predicted for Kudahuvadhoo. Hazard Scenario Probability Potential Major Environmental Impacts at Location Tsunami (maximum scenario) 3.2m Low Widespread damage to coastal vegetation (Short-term) Long term or permanent damage to selected inland vegetation especially common backyard species such as mango and breadfruit trees. Contamination of ground water if the sewerage systems are damaged or if liquid contaminants such as diesel and chemicals in the boat yard are leaked. Salinisation of ground water lens to a considerable period of time causing ground water shortage. If the rainwater collection

51 Hazard Scenario Probability at Location Storm Surge (based on UNDP, (2005)) 0.60m (1.53m Very Low storm tide) Potential Major Environmental Impacts facilities are destroyed, potable water shortage would be critical. Widespread damage to crops Moderate to major damage to coastal protection and island access infrastructure such as breakwaters and quay walls. Short-medium term loss of soil productivity (southern agricultural zone) Minor damage to coral reefs (based on UNEP (2005)) Minor damage to coastal vegetation Minor loss of crops Minor damage to coastal protection infrastructure Minor geomorphologic changes in the southern oceanward shoreline and lagoon Strong Wind Knots Very High Minor damage to very old and young fruit trees Debris dispersion near waste sites. Minor damage to open field crops Knots Low Moderate damage to vegetation with falling branches and occasionally whole trees Debris dispersion near waste sites. Moderate-high damage to open field crops Minor changes to coastal ridges 65+ Knots Very Low Widespread damage to inland vegetation Debris dispersion near waste sites. Minor changes to coastal ridges Heavy rainfall 187mm Moderate Minor to moderate flooding in low areas, including roads and houses. 242mm Low Widespread flooding but restricted to low areas of the island. Drought Low Minor damage to backyard fruit trees and crops Earthquake Low Minor geomorphologic changes to land and reef system. Sea Level Rise by year 2100 (effects of single flood event) Medium (0.41m) Moderate Widespread flooding during high tides and surges. Loss of land due to erosion. Loss of coastal vegetation Major changes to coastal geomorphology. Saltwater intrusion into water lens and salinisation of ground water leading to water

52 Hazard Scenario Probability at Location Potential Major Environmental Impacts shortage and loss of flora and fauna. Minor to moderate expansion of wetland areas 3.6 Findings and Recommendations for safe island development plan A coral islands main defensive ability against frequent natural hazards is perhaps its robust natural adaptive capacity. In order to retain this ability against ocean induced hazards, a proper and functioning coastal environment is essential. It takes a number of years in term of geological time for an island to stabilise and achieve equilibrium in processes around the island. Once established the island evolves and adapts to the prevailing conditions. The natural history of Maldives bears evidence to such natural adaptation, including the survival through a 2.5m rise in sea level (Kench et.al, 2004). It is perhaps the foremost reason why the coral islands of Maldives have survived thus far. The proposed safe island development in Kudahuvadhoo proposes to change a functioning coastal environment into a more artificial environment. The implications of this change are numerous especially in the short term. The proposed modifications may require considerable time for the island to achieve equilibrium in different forces controlling coastal processes. During this period considerable changes to the existing coastal environment may be imminent. In the absence of coastal protection, these changes would be more noticeable. There is a high probability that the proposed coastal modifications would expose Kudahuvadhoo to the following ocean induced hazards. There could be a rapid onset of erosion in specific areas of the island in the short-term until the coastal environment achieves an equilibrium. The present shape of the coastline is a result of the prevailing condition within the reef. Considerable changes to unaltered zones of the island are highly probable. Hence, coastal erosion hazards may in general be increased. Island topography and resulting drainage systems are critical features of an island in relation to exposure to natural hazards. Safe island development plan of Kudahuvadhoo should consider the existing topography and implications of

53 modifying the topography on the rainfall related flooding. Such activities include reclamation activities proposed in the southern end of the island. Kudahuvadhoo has considerable topographic variations. The proposed new settlement expansion areas fall into significant low areas of the island which in the future may be exposed to rainfall related flooding. Similarly, the function of the low drainage areas in the Environment Protection Zone (EPZ) needs to be reviewed. Given the topographic variations within Kudahuvadhoo, the proposed 0.1m variation in the drainage area may not have the desired effects on flood control. In the southern areas where there are multiple ridges, the proposed drainage area simply may have no function while in the western areas it may lead to rainfall related flooding unless siltation-proof drainage systems are installed. Based on the 9 islands studies in this project, it has been observed that strong coastal vegetation is amongst most reliable natural defences of an island at times of ocean induced flooding, strong winds and against coastal erosion. The design of EPZ zone needs to be reviewed to consider the important characteristics of coastal vegetation system that is required to be replicated in the safe island design. The width of the vegetation belt, the composition and layering of plant species and vegetation density needs to be specifically looked into, if the desired outcome from the EPZ is to replicate the coastal vegetation function of a natural system. Based on our observations, the proposed width of coastal vegetation in the standard Safe Island Design may not be appropriate for reducing certain ocean induced hazard exposures. The timing of vegetation establishment also needs to be clearly identified in the safe island development plan. 3.7 Limitations and recommendations for further study The main limitation of this study is the lack of time to undertake more empirical and detailed assessments of the island. The consequence of the short time limit is the semi-empirical mode of assessment and the generalised nature of findings. The lack of existing survey data on critical characteristics of the island and reef, such as topography and bathymetry data, and the lack of long term survey data such as that of wave on current data, limits the amount of empirical assessments that could be done within the short timeframe.

54 The topographic data used in this study shows the variations along two main roads of the island. Such a limited survey will not capture all the low and high areas of the island. Hence, the hazard zones identified may be incomplete due to this limitation. This study however is a major contribution to the risk assessment of safe islands. It has highlighted several leads in risk assessment and areas to concentrate on future more detailed assessment of safe islands. This study has also highlighted some of the limitations in existing safe island concept and possible ways to go about finding solutions to enhance the concept. In this sense, this study is the foundation for further detailed risk assessment of safe islands. There is a time scale mismatch between environmental changes and socioeconomic developments. While we project environmental changes for the next 100 years, the longest period that a detailed socio-economic scenario is credible is about 10 years. Uncertainties in climatic predictions, especially those related Sea Level Rise and Sea Surface Temperature increases. It is predicted that intensity and frequency of storms will increase in the India Ocean with the predicted climate change, but the extent is unclear. The predictions that can be used in this study are based on specific assumptions which may or may not be realized. The following data and assessments need to be included in future detailed environmental risk assessment of safe islands. A topographic and bathymetric survey for all assessment islands prior to the risk assessment. The survey should be at least at 0.5m resolution for land and 1.0m in water. Coral reef conditions data of the house reef including live coral cover, fish abundance and coral growth rates. At least a years data on island coastal processes in selected locations of Maldives including sediment movement patterns, shoreline changes, current data and wave data. Detailed GIS basemaps for the assessment islands. Coastal change, flood risk and climate change risk modeling using GIS.

55 Quantitative hydrological impact assessment. Coral reef surveys Wave run-up modelling on reef flats and on land for gravity waves and surges. References UNDP (2006), Disaster risk profile of Maldives IDPA report IPCC (1990). Strategies for Adaptation to Sea-Level Rise: Report of the Coastal Management Subgroup. Strategies for Adaptation to Sea-Level Rise: Report of the Coastal Management Subgroup. IPCC Response Strategies Working Group. Cambridge, University of Cambridge. IPCC (2001). Climate Change 2001: Impacts, Adaptation, and Vulnerability. Cambridge, United Kingdom and New York, NY, USA, Cambridge University Press. Kench, P. S. and P. J. Cowell (2002). "Erosion of low- lying reef islands." Tiempo 46: Kench, P. S., R. F. McLean, et al. (2005). "New model of reef-island evolution: Maldives, Indian Ocean." Geology 33(2): Ministry of Planning and National Development (MPND) (2005). Infrastructure Development for Poverty Alleviation, Volume II - L.Gan. Male', Maldives, Ministry of Planning and National Development. Pernetta, J. and G. Sestini (1989). The Maldives and the impact of expected climatic changes. UNEP Regional Seas Reports and Studies No Nairobi, UNEP. UNEP (2005). Maldives: Post-Tsunami Environmental Assessment, United Nations Environment Programme. United Nations Development Programme (UNDP) (2005). Disaster Risk Profile for Maldives. Male', UNDP and Government of Maldives. Woodroffe, C. D. (1989). Maldives and Sea Level Rise: An Environmental Perspective. Male', Ministry of Planning and Environment: 63.

56 Woodroffe, C. D. (1993). Morphology and evolution of reef islands in the Maldives. Proceedings of the 7th International Coral Reef Symposium, Guam, University of Guam Marine Laboratory. 2: Yamano, H. (2000). Sensitivity of reef flats and reef islands to sea level change. Bali, Indonesia.

57 4. Structural vulnerability and impacts 4.1 House vulnerability Not surveyed. 4.2 Houses at risk As shown in Fig. 4.1 and Fig. 4.2, no houses are exposed to flooding for the time being. However, the situation will be subjected to a small change in the further after the establishment of new settlements in the eastern side of the island, according to a new land use plan updated most recently. Even if it is the case, the exposure of houses to major flood hazards is very limited. Still no houses are located in the swell wave / surge flood-prone area and only about 19 houses, accounting for less than 1% of the total houses, are exposed to tsunami floods. More houses (more than 20%) are affected by rainfall floods, but damage is very limited due to the low intensity of rainfall floods (Table 4.1). only the contents of exposed houses may be subjected to some degree affected. In all, houses on Kudahuvadhoo Island are at very low risk. Table 4.1 Houses at risk on Dh. Kudahuvadhoo. Exposed Vulnerable Potential Damage Hazard houses houses Serious Moderate Slight Content type # % # % # % # % # % # % TS 19 8 Flood W/S RF Earthquake Wind Erosion

58 Fig. 4.1 Houses at risk associated with Tsunami floods.

59 Fig. 4.2 Houses at risk associated with rainfall floods (left) and wave / surge floods (right).

60 4.3 Critical facilities at risk As shown in Fig. 4.3 and 4.4, critical facilities that are exposed to floods are 2 schools, a mosque, a power house, and a proposed waste disposal site and waster water treatment plant. Located in the low-lying center of the island, 2 schools and a mosque may be subjected to rainfall floods of very low intensity, but no physical damage is expected, given the physical conditions at present. Located in the eastern coast, power house is exposed to ocean-originated floods. Although no physical damage is expected, its contents may be subjected to flooding. In addition, two waster processing facilities, proposed to be located in the southern side of the island, will be subjected to ocean-originated flooding as well. Flooding of these two facilities may cause secondary contamination to groundwater system and sewerage system. In all, critical facilities on Kudahuvadhoo Island are at low risk, although located in hazard-prone areas. However, some mitigation measures are necessary to retrofit power house and waste sites or reconsider the location of waste sites. Table 4.2 Critical facilities at risk on Kudahuvadhoo Island. Critical facilities Potential damage/loss Flood Hazard type Tsunami Wave/Surge Exposed Vulnerable Physical damage Monetary value Power house, waste none Content-affected N/A site, boat repair Power house, waste none Content-affected N/A site, boat repair Rainfall 2 schools, 1 mosque none No N/A Earthquake Wind Erosion

61 Fig. 4.3 Critical facilities at risk associated with rainfall floods.

62 Fig. 4.4 Critical facilities at risk associated with swell wave/surge and tsunami floods.

63 4.4 Functioning impacts Although causing no physical damage to most critical facility buildings, major flooding events may impact the functioning of critical facilities (Table 5.3). For example, power house and associated distribution network may fail to operate for days wave/surge and tsunami flooding; Inundation of the waste disposal site can cause a secondary contamination to the sensitive groundwater system of the island, which further affect the supply of potable water supply.school activities may be interrupted for days by rainfall floods as well. Table 4.3 Potential functioning impacts Function Flood Tsunami Wave/surge Rainfall Earthquake Wind Administration 1) Health care Education days Religion Housing Sanitation 3) Secondary contamination Water supply Power supply A day Transportation Communication 2) Note: 1) Administration including routine community management, police, court, fire fighting; 2) Communication refers to telecommunication and TV; 3) Sanitation issues caused by failure of sewerage system and waste disposal.

64 4.5 Recommendations for risk reduction According to the physical vulnerability and impacts in the previous sections, the following options are recommended for risk reduction of Kudahuvadhoo: Avoid locating proposed waste disposal site and waste water plant in the flood-prone area; Retrofit the power house on the northeastern coast.

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