An Assessment of the Coastal Dynamics of the North Coast of Trinidad

Transcription

1 An Assessment of the Coastal Dynamics of the North Coast of Trinidad Charmaine O Brien-Delpesh Institute of Marine Affairs, Hilltop Lane, Chaguaramas

2 Background of IMA s Coastal Conservation Project Since the early eighties, the IMA has been monitoring the beaches of Trinidad and Tobago to determine Stability trends Erosion/Accretion rates and To assess the effects of coastal development on the shorelines of Trinidad and Tobago 70 Beach Monitoring Stations have been established in Trinidad and 42 in Tobago Beach Profiles and Littoral Processes data were collected monthly from 1990 to 1995 and quarterly from 1996 to present. Sediment data are also collected annually. A database has been developed for the Coastal Conservation Project

3 Map Showing IMA Stations around Trinidad

4 Data Collected Beach Profiles, from which beach sediment volume, beach width and intercept of the beach with Mean Sea Level / Low Water are determined Wind Speed and Direction, Breaking Wave Height, Wave Period, Wave Approach, Type of Breaker, Longshore Current (Speed & Direction) and Beach Sediment

5 Uses of the Data Data is used to advise Town and Country Planning Division of the Ministry of Planning and Development on required building setbacks for coastal development projects. To provide advice to the Environmental Management Authority and Lands & Surveys Division and other Government agencies on coastal development / activities Data is provided to students for research projects and It is sold to the private and public sectors

6 Coastal Classification for Trinidad PORT OF SPAIN COASTS ROCKY CLIFFS LOW CLIFFS PLAINS DUNES WET LANDS SHORES BEACHES MUD FLATS BUILT UP AREAS COASTAL OTHER GULF OF PARIA ATLANTIC OCEAN SAN FERNANDO COLUMBUS CHANNEL

7 East Coast Cocos Bay Eroding shoreline Fallen trees Fallen coconut trees Fallen trees at Northern Mayaro Bay The coastal area of Cocos Bay between the Nariva and Ortoire Rivers is eroding. Along some sections of the Manzanilla-Mayaro Road the High Water Line is approximately 8 metres from the road. During swell events uprush reaches the road, which is being threatened. Some type of coastal protection is needed to arrest erosion and protect the road. IMA Vehicle parked on the road, Cocos Bay

8 South Coast On the south coast, the geological outcrops consist mainly of unconsolidated silts, clays and sandstones, which provide little resistance to oncoming waves. The entire coastline of Guayaguayare Bay except for the areas of the Wetland at the eastern part of the bay has been eroding for the last century. From 1996 to present the western part of the bay has been altered due to the laying of gas pipelines. The coastline at the central section of Guayaguayare Bay receded 3.9 metres during the period IMA Station 3 Punta Del Arenal One of the few coastal areas where accretion is taking place, is at Punta del Arenal. Within the last 14 years the beach has accreted vertically and migrated approximately 28 metres seaward. Eroding shoreline Guayaguayare Bay

9 West Coast Height= 1.3 m Fallen trees at Columbus Bay Clifton Hill Seawall, Guapo Bay The shoreline of the west coast of Trinidad has been experiencing erosion over decades even though this is the most sheltered coastline of Trinidad. During the last 20 years this shoreline has changed significantly as a result of erosion, coastal development, reclamation and coastal structures. Reclamation at Westmoorings

10 Beaches along the North Coast of Trinidad monitored by IMA PORT OF SPAIN ARIMA m m Turtle Nesting Sites Coastline Roads

11 Macqueripe Bay

12 Macqueripe Bay Characteristics & Uses Sheltered bay bounded by densely vegetated headlands Small pocket beach, 117 m long and 16 m wide. Low moderate waves from the west with a weak longshore current Water usually clear and generally calm but occasionally rough from Nov April Uneven seabed with fringing reef offshore Beach is in dynamic equilibrium Good for swimming, snorkeling & SCUBA diving Fishing takes place off the concrete jetty Hiking trails in the mountains bounding the bay Parking & Change rooms available No lifeguards on duty

13 Macqueripe Bay Coastal Management Issues Concrete platform is in the active beach zone thereby affecting beach processes Concrete steps leading to beach can be hazardous when wet Security and safety needs to addressed i.e. lifeguards and proper lighting Limited land space for development

14 Concrete platform 16m Macqueripe Bay

15 h Maracas Bay

16 Maracas Bay Characteristics & Uses Bay is bounded by two prominent headlands Three rivers enter the bay Small swamp located south of the road Fairly wide beach (30 m) with flat backshore Strong offshore winds Large waves (avg 0.77m) and rough waters most of the year Rip currents create an uneven sea floor Moderate Strong longshore current Beach is in dynamic equilibrium Swimming, sun bathing, body surfing & camping Ball games in backshore area (e.g. volleyball, football) Vending (food & craft) Parking and change rooms Life guards Hotel Fishing Depot

17 h Maracas Bay Coastal Management Issues Not an ideal bathing beach because of the risk to bathers due to strong currents and effluent discharge Loss of beach sand in the absence of sediment traps Wind blown sand is a hazard to vendors and visitors Seasonal erosion at eastern end of the beach due to winter swells Flooding of inland area due to reclaimed swamp land and inadequate drainage Discharge of effluent into river creates health issues Lack of enforcement of no parking zones Absence of zoning for water craft (jet skis) Crossing the road can be a hazard to pedestrians

18 Las Cuevas Bay

19 Characteristics & Uses Las Cuevas Bay Bay protected by prominent headlands Fairly wide (34 m) gently sloping beach Western half of the bay is backed by low lying plains Eastern half backed by low steep cliffs River enters the bay at western end Very little coastal development except at eastern end (beach and fishing facilities) Large waves (> 0.8m) and weak longshore current mostly at the eastern end. Rip currents present Parking and change facilities Lifeguards at eastern end only Fishing depot Beach is in dynamic equilibrium Swimming, sun bathing & fishing

20 1.8 Winter Months Summer Months 1.6 BREAKER HEIGHT (m ARTHUR WINTER STORM WINTER STORM BRET LENNY YEAR Breaker Heights Las Cuevas Bay

21 Las Cuevas Bay after Hurricane Lenny December 1999

22 Las Cuevas Bay Coastal Management Issues Susceptible to damage from hurricanes Erosion of the cliffs at the eastern end Inadequate parking facilities Safety a problem at the western end: no lifeguards and the area is remote Limited access to the western end of the bay Beach access (walkway) at the beach facilities, can be hazardous for visitors

23 Blanchisseuse Bay

24 Blanchisseuse Bay Characteristics & Uses Absence of prominent headlands offers little protection to the bay Very narrow beach (10m) Sea is generally rough (1.1m breaking height) with strong longshore and rip currents River enters at the eastern end Small offshore rock reef at the eastern end Plunge point present (0.45m in depth) Beach is eroding Swimming, fishing, surfing, snorkeling, vending and camping

25 m Mar 1989 May 1994 Aug 1999 Mar 2004 ELEVATION (m) Benchmark MEAN SEA LEVEL (M.S.L.) DISTANCE FROM BENCHMARK (m) Selected Profiles for IMA's Beach Monitoring Station 2, Blanchisseuse Bay

26 Blanchisseuse Bay Coastal Management Issues Erosion of shoreline in the vicinity of coastal development Large waves, strong currents and a plunge point can be hazardous to swimmers Unapproved coastal development Access to the beach and parking are on private property Absence of beach facilities, public car park and lifeguards

27 Grande Riviere Bay

28 Swimming, fishing, turtle watching, camping, surfing Grande Riviere Bay Characteristics & Uses Large, densely vegetated headlands offer protection to the bay River enters the bay at eastern end (shifting river mouth) Very dynamic beach, 1.2 km long Rough sea (waves > 1.0m in height) with moderate longshore current Hotels and Guest houses Beach is in dynamic equilibrium Plunge point present ( x m in depth)

29 Grande Riviere Bay Coastal Management Issues Bathing unsafe from Nov Apr when waves reach 2.0m in height Inland flooding Limited access to the beach Coastal developers need to be aware of the sensitivity of the beach as a turtle nesting site

30 Salybia Bay

31 Salybia Bay Characteristics & Uses Small bay (700m long), with narrow (10m wide), white sandy beach Fringing Reef offers some protection to the beach River enters at the eastern end Large, flat backshore area with coconut palm trees Very strong westerly longshore current (up to 1.0 m/s) in the area of the reef Western part of the bay is deep Beach is in dynamic equilibrium Swimming, snorkeling, picnicking & camping

32 Salybia Bay Coastal Management Issues Lack of a designated parking area Beach facilities are absent No lifeguards present No lighting Insufficient disposable system for solid waste Reef walking Safety at sea is a concern because of the strong currents Camping takes place in the absence of adequate facilities & amenities (toilets, parking)

33 Coastal Stability of Trinidad

34 Coastal Issues that should be addressed Effluent discharge into rivers Inadequate drainage Posting of hazard signs e.g. showing unsafe bathing areas Education programmes about hazards at sea (rip currents & harmful marine life) Lifeguards needed on other popular beaches Beach security beach police to address issues such as illegal parking and unlawful behaviour, and to assist lifeguards with security issues that may affect the general safety of visitors to the beaches Zoning of coastal activities such as camping, water craft (jet skis), vending, etc

35 Recommendations based on IMA s Coastal Monitoring Programme Enforcement of setback distances recommended by TCPD to developers Conduct coastal research on water and sediment quality, ecology, oceanography and beach and sediment dynamics

36 Acknowledgements Institute of Marine Affairs Jonathan Gomez - Photography Kevin Khan Data Collection, Photography, Presentation Steve Lalbeharry Data Collection, Photography Lori Lee Lum - Photography Sunil Ramnath Data Collection, Photography Gregory Pantin Preparation of Maps

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38 3.0 Apr 1988 Old Benchmark Jun New Concrete Platform Seawall Jul 1999 May Benchmark 0.6 m 0.0 MEAN S EA LEVEL (M.S.L.) DISTANCE FROM BENCHMARK (m) Selected Beach Profiles for IMA's Beach Monitoring Station at Macqueripe Bay April 1988, June 1993, July 1999 & May 2004

39 Selected Beach Profiles for IMA's Beach Monitoring Station 2, Maracas Bay March 1985, July 1991, April 1998 & April 2004

40 Selected Beach Profiles for IMA's Beach Monitoring Station at Las Cuevas Bay March 1985, June 1991, July 1998 & March 2004

41 Selected Profiles for IMA's Beach Monitoring Station 2, Grande Riviere Bay May 1999, June 2001 & August 2003

42 Selected Profiles for IMA's Beach Monitoring Station at Salybia Bay April 1989, March 1994, July 1999 & March 2004