Guideline: A risk assessment approach to development assessment in coastal hazard areas

Transcription

1 Guideline: A risk assessment approach to development assessment in coastal hazard areas

2 Prepared by: Environment Planning, Department of Environment and Heritage Protection State of Queensland, The Queensland Government supports and encourages the dissemination and exchange of its information. The copyright in this publication is licensed under a Creative Commons Attribution 3.0 Australia (CC BY) licence. Under this licence you are free, without having to seek our permission, to use this publication in accordance with the licence terms. You must keep intact the copyright notice and attribute the State of Queensland as the source of the publication. For more information on this licence, visit Disclaimer This document has been prepared with all due diligence and care, based on the best available information at the time of publication. The department holds no responsibility for any errors or omissions within this document. Any decisions made by other parties based on this document are solely the responsibility of those parties. Information contained in this document is from a number of sources and, as such, does not necessarily represent government or departmental policy. If you need to access this document in a language other than English, please call the Translating and Interpreting Service (TIS National) on and ask them to telephone Library Services on This publication can be made available in an alternative format (e.g. large print or audiotape) on request for people with vision impairment; phone or <library@ehp.qld.gov.au>. April 2013

3 Contents Purpose...1 Background...1 What are coastal hazards?...1 Temporary inundation (storm tides)...1 Permanent inundation...1 What is risk?...2 What is risk mitigation?...2 Risk assessment Identify if the development site is affected by coastal hazards If the site is affected by coastal hazards then determine the nature and extent of the hazard Determine the impact of the inundation on the proposed development Identify potential mitigation measures Assess the viability of mitigation measures both onsite and offsite, taking into account environmental, social and financial factors Select preferred mitigation measures...7 iii

4 Purpose The draft State planning policy sets out the state interest for natural hazards that is, the risk of, and the adverse impacts from natural hazards are avoided, minimised or mitigated to protect people and property and enhance the community's resilience to natural hazards. This guideline has been prepared to assist local government in assessing development applications to addresses the coastal hazard(s) and associated risks to people, property, economic activity, social wellbeing and the environment. Background A high proportion of Queensland s urban development is located in the coastal zone, with some development located in areas vulnerable to coastal hazards. Coastal hazard areas are those areas that are at risk from coastal erosion or storm tide inundation. Coastal hazard risks are not new; however projected sea level rise will increase the risk from coastal hazards and cause the permanent inundation of low lying land. This increasing coastal hazard risk will occur over a long timeframe and significant changes are generally not projected to be experienced until 2030 or later. However, development decisions can have long-term implications and most urban development cannot easily be relocated. History has demonstrated that the conversion of land use from a lower to high intensity use is considered permanent and development is generally defended from hazard impacts. Projected sea level rise will challenge the financial and physical capacity of communities to continue to defend people and property. What are coastal hazards? Coastal hazards consist of temporary inundation from storm tides and permanent inundation as a result of shoreline erosion or sea level rise. Temporary inundation (storm tides) While storm tide inundation is an infrequent event, it is not rare in Queensland and the effects on life and property can be dramatic. Unlike coastal erosion and permanent loss of land from sea level rise, storm tides do not permanently inundate areas and inundation occurs over a period of hours or days. The frequency, depth and longevity of inundation changes with elevation above the highest astronomical tide level (HAT) in simple terms HAT is the highest point a tide reaches during a year. People and development located on land that is flooded to a depth of a metre or more during a defined storm-tide event are at significant risk. This is due to the water depth being sufficient to generate damaging waves and the strength of the tidal flows. Permanent inundation Permanent inundation as a result of sea level rise will be experienced as shoreline erosion events in which the original extent of the foreshore never recovers from an erosion event. While sea level rise is projected to accelerate over the next 100 years as a consequence of climate change, the permanent loss of land from a rise in sea level will become apparent as accelerated coastal erosion. Sea levels will not rise evenly. Without climate change, sea levels constantly vary as a result of processes such as slight changes in the orbit of the earth, associated tide changes and climate variability. Rising sea levels will be most noticeable during extreme sea level events such as king tides. This is because existing extreme events in sea level variability will be exacerbated by rising sea levels. Further information about the methodology used to determine coastal hazard areas, and guidance about determining areas at risk from coastal hazards can be found in the Coastal Hazards Technical Guide, available on the EHP website 1

5 What is risk? Risk can be described as the frequency of a hazardous event occurring relative to the consequences of the event. A risk assessment is the means used to evaluate risks associated with a specific hazard for a particular development in terms of the probability or likely frequency of occurrence, severity, exposure of an event and the consequences for the development. Risk = Frequency X Consequence To implement effective risk mitigation measures, the potential impact on a development as a result of being affected by a defined coastal hazard must first be appraised through identifying: Hazard identifying the nature, extent and likely frequency of the coastal hazard(s) Asset determining the nature and scale of the development that is at risk from the coastal hazard(s) Vulnerability evaluating the consequence of coastal hazard impacts on people, property and the operation of the development over its functioning life. What is risk mitigation? Coastal hazard risk mitigation is any sustained action taken to avoid the long-term risk generated by hazards to people, property, economic activity, social wellbeing and the environment. Risk mitigation actions can take many forms, including siting of structures, building design, protective works (erosion control structures), land use regulation and retention or enhancement of natural buffers. Image 1: Hurricane Floyd (1999) brought a 4.5m storm surge that damaged or destroyed hundreds of houses along Long Beach on Oak Island, NC (USA). Here is a prime example of mitigation working the elevated house on the right was still standing after the hurricane. The older, ground-level block foundation of the home on the left was crushed. Image credit: Dave Gately/FEMA News Photo. Risk assessment A coastal hazard risk assessment can be undertaken to evaluate the risk to a proposed development from coastal hazards. This can assist in determining the most appropriate mitigation measures for the development site. In accordance with the draft State Planning Policy, a coastal hazard risk assessment can be undertaken to evaluate whether: the development is compatible with the level of risk associated with the hazard(s) the development siting, layout and access responds to a potential coastal hazard and minimises risk to personal safety 2

6 the development is resilient to coastal hazard events by ensuring siting and design accounts for the potential risks of coastal hazards to property the development directly, indirectly and cumulatively avoids an unacceptable increase in the severity of the coastal hazard and does not significantly increase the potential for damage on the site or to other properties the development avoids the release of hazardous materials as a result of a coastal hazard event natural processes and the protective function of landforms and/or vegetation are maintained in coastal hazard areas. 1 A risk assessment can demonstrate that adverse coastal hazard impacts from the defined storm tide event and projected sea level rise that would otherwise affect the operational and structural integrity of the development are avoided, minimised or mitigated. This includes ensuring the development is able to continue to function and maintain its design lifespan without maintenance or repair beyond the normal requirements for a development of its type. The risk assessment can describe how these impacts are avoided through location, design, construction and operating standards including any existing coastal protection works. The detail included in a risk assessment will vary depending on the scale and complexity of development proposed. However this guideline recommends that a risk assessment be developed using the following steps: 1. Identify if the development site is affected by coastal hazards 2. If the site is affected by coastal hazards then determine the nature and extent of the hazard 3. Determine the impact of the inundation on the proposed development 4. Identify potential mitigation measures 5. Asses the viability of mitigation measures both onsite and offsite, taking into account environmental, social and financial factors 6. Select preferred mitigation measures. This process aligns with the Australian and New Zealand Risk Management Standards (AS/NZS ISO 31000). 1. Identify if the development site is affected by coastal hazards Establish whether the site is affected by coastal hazards. Local governments are encouraged to undertake local-scale coastal hazard assessment studies for urban and periurban areas. With respect to coastal erosion, EHP has declared erosion prone areas along the coast and this is generally suitable for consideration in assessment processes. Where local studies have not been undertaken, a development proponent or local government should use the Queensland Government coastal hazard area mapping as a basis to establish whether the site is likely to be affected by coastal hazards (refer to the example in Figure 1). The Queensland Government maps are indicative of the extent of Queensland s coastal areas projected to be at risk from coastal hazards at the year Each map shows: areas to be permanently inundated a result of either shoreline erosion or sea-level rise a defined storm-tide inundation area medium hazard and high hazard temporary inundation areas. In these maps storm tide inundation is based on default values of 1.5m above highest astronomical tide (HAT) for southeast Queensland and 2.0m above HAT for the remainder of the State. 1 In addition, for development in a coastal hazard area, erosion prone areas in a coastal management district are to be maintained as development-free buffers or where permanent buildings or structures exist, coastal erosion risks are avoided or mitigated. 3

7 Figure 1: Example of Queensland s coastal hazard area maps The coastal hazard area maps are available on the Department of Environment and Heritage Protection's (EHP) website at: Declared erosion prone area plans available on the EHP website at The digital data for coastal hazards can be obtained from the Queensland Government Information Service (QGIS) website Direction on undertaking local scale hazard studies is provided in the 'Coastal Hazards Technical Guide' available at 2. If the site is affected by coastal hazards then determine the nature and extent of the hazard Determine the nature of the hazard (temporary or permanent inundation) and the extent of inundation (depth and area) on the site. A survey of the site should be undertaken to create a property scale plan. The survey should be undertaken by a registered surveyor to determine the depths of inundation across the development site. The plan should include relevant contours showing the topography of the site at a scale necessary to identify potential inundation depths. This will assist in determining whether the development is compatible with the level of risk associated with the hazard. 3. Determine the impact of the inundation on the proposed development Consider the impact of the coastal hazard on the proposed development (its operation and structural integrity) and to people living or working onsite. The nature and extent of a coastal hazard is measured assuming no mitigation measures are employed. The measure of impact of the hazard on the development must consider its structural integrity over the life of the development, the safety and wellbeing of people, effect on short and long term operations and whether the development is an essential community service. In many cases, an event will expose the development to multiple hazards (e.g. inundation and erosion). The risk assessment should account for all the potential coastal hazards for a given event in order to accurately determine vulnerability. The vulnerability of a development to the impact of a coastal hazard will largely relate to the type, nature and extent of the development proposed. For example, a nursing home or hospital will be more vulnerable to coastal hazard impacts due to its occupants and services it provides when compared with an industrial area. Conversely, the inundation of industrial areas might result in inherent risks such as the escape of toxic or hazardous materials. For commercial development, the loss of stock or productive capacity should also be considered. 4

8 4. Identify potential mitigation measures Identify potential measures for the development (including its operation) that addresses the coastal hazard and associated risks to people, property, economic activity, social wellbeing and the environment for the life of the use of the site. There may be different responses should the hazard be permanent inundation compared to temporary inundation. This may include siting, design and response options such as: filling land above the inundation level (or partial filling combined with other actions) habitable rooms 2 of the built structure being located above the assessed inundation level a safe refuge available for people within the development site (appropriate for a temporary inundation event) a safe evacuation route above the inundation level essential operational services (electricity switchboards; pumps; hot water systems) that are located so they are not inundated during a hazard event associated infrastructure such as roads are located or constructed so they are not permanently inundated. Table 1 summarises factors and possible mitigation measures that should be considered for addressing the coastal hazard and associated risks to people, property, economic activity, social wellbeing and the environment. Examples of mitigation measures are also provided in figures 2 and 3. Table 1: Summary of factors to consider for addressing coastal hazards and possible mitigation measures Possible factors to consider Possible mitigation measures Permanent inundation due to sea level rise. The impact of a defined storm tide inundation event on associated infrastructure such as roads, transport networks, educational or recreational facilities. More frequent overflows from stormwater networks. Rising groundwater in response to sea level rise. Increased erosion along foreshores which results in asset losses and damage. High demands on emergency relief agencies and the need for clear evacuation routes should the need arise. Losing beaches in front of coastal protection works. On-going maintenance costs for coastal protection works or beach nourishment. Capacity for coastal ecosystems to migrate landward as sea level rises. Location Design Construction Locate habitable buildings outside of, or as far landward of the coastal hazard area as possible (e.g. see Figure 2). Minimise the footprint of the development on that part of the site within the coastal hazard area. Allow for natural barriers or buffers on or adjacent to the site. Fill land above defined temporary or permanent inundation level. Design habitable buildings so that habitable rooms remain above the temporary inundation level (see e.g. Figure 3). Design the development so that operational components remain above the level of temporary or permanent inundation or waterproof components if located below temporary inundation level. Use landscaping to prevent water intruding into parts of the development that may be more vulnerable to inundation or guide water into areas where there are no vulnerable structures. This may include the use of natural vegetation barriers that can reduce the effect of a storm tide. Buildings or structures to be decommissioned, disassembled or relocated either on the site or to another site. Install and maintain on-site erosion control 2 Under the Building Code of Australia, 'habitable room' is a room used for normal domestic activities, and: a) includes a bedroom, living room, lounge room, music room, television room, kitchen, dining room, sewing room, study, playroom, family room, home theatre and sunroom; but b) excludes a bathroom, laundry, water closet, pantry, walk-in wardrobe, corridor, hallway, lobby, photographic darkroom, clothes drying room, and other spaces of a specialised nature occupied neither frequently nor for extended periods. 5

9 Possible factors to consider Possible mitigation measures structures. 3 Operating standards Identify or design evacuation routes above inundation level. Locate a safe refuge for people within the development site. Built structures to be operational during and after a coastal hazard event. The building assessment provisions under the Building Act 1975 provide the construction requirements for buildings and structures in Queensland. Under the Building Code of Australia, a building or structure must withstand the combination of loads and other actions to which it may reasonably be subjected. It is recommended that homeowners check with building certifiers or other buildings professionals for the building requirements applicable in coastal hazard areas. The document 'Rebuilding in storm tide prone areas: Tully Heads and Hull Heads' provides further information on housing construction and rebuilding in storm tide areas, available at Before After Townhouses are located outside the hazard area on the site Common garden and/or parking area is located in the hazard area on the site Figure 2: Example of built structures for accommodation or employment purposes being located outside of a coastal hazard area. 3 Under the State Planning Policy, development in a coastal hazard area ensures that coastal protection work is undertaken only as a last resort where erosion presents an imminent threat to public safety or property, and (i) the property cannot be reasonably be relocated or abandoned; (ii) the coastal protection work is located on private land to the maximum extent reasonable; (iii) the coastal protection work does not increase coastal hazard risk for adjacent areas. 6

10 Before After Habitable rooms are elevated above the temporary storm-tide inundation level (shown in red as the level of DSTE (defined storm tide event). Relevant outdoor utilities are elevated above the temporary inundation level (e.g. air conditioning units, electrical boxes, hot water systems). Figure 3: Example of habitable rooms in built structures for accommodation or employment purposes being located above the defined storm tide event level. 5. Assess the viability of mitigation measures both onsite and offsite, taking into account environmental, social and financial factors Assessing the viability of potential mitigation measures includes considering the impact of the options on the development itself, associated infrastructure, neighbouring land use and development and public amenity taking into account long-term environmental, social and financial considerations. For example, the environmental costs of protection works should be taken into account, particularly considering the effects of climate change and the preference to maintain natural coastal processes. In comparison, natural environmental features can protect and buffer communities and infrastructure from sea level rise and coastal inundation. Assessing the viability of potential mitigation measures should also consider the most cost-effective manner in which to mitigate the risk. Locating the development outside of a coastal hazard area may be the most costeffective mitigation measure. However this does not consider that many urban areas along the Queensland coast are already built up and already occur in coastal hazard areas. In this context, the cost of setting back the development, fill the development site, constructing coastal protection structures or building design measures should be weighed against the value, use and vulnerability of the development. Consideration must also be made to minimising any increase of shoreline erosion on areas adjacent to the development site and maintaining physical coastal processes outside the development area where erosion control structures are proposed. 6. Select preferred mitigation measures After assessing the viability of potential mitigation measures, the preferred option(s) are to be identified and described in the development application in order to avoid, minimise or mitigate coastal hazard risks to protect people and property and enhance the community s resilience to coastal hazards. 7