Wednesday, 30 May 2012

Assessing the Risk of Sea Level Rise: The Way Forward for Sri Lanka

By S.S.L.Hettiarachchi and S.P.Samarawickrama
Department of Civil Engineering, University of Moratuwa

Climate Change and Sea Level Rise  
Climate change will have significant impacts on the oceans and on the coastal zone on a global scale. It will introduce new hazards and increase existing hazard potential, both with respect to magnitude and frequency of occurrence, in coastal regions. The hazards would be both chronic (e.g., sea level rise) and episodic (e.g., storm events). Sea level rise is one of the more certain responses to global warming and presents a major challenge in the administration and management of coastal zones, including that of Sri Lanka. A large percentage of Sri Lanka’s population is located in coastal regions and these regions play a vital role in the economic growth of the country.

Sri Lanka is one of the few countries which have a fully operational National Coastal Zone Management Plan, and the Government’s Coast Conservation Department has  full responsibility for its implementation. In Sri Lanka, the Coast Conservation Act has defined the coastal zone on geo-physical considerations using linear dimensions. This narrow and geographically defined coastal zone does not recognize the interconnections within coastal ecosystems, its resources, and the human interactions. This limitation in the definition of the coastal zone could become a critical constraint when implementing action plans to respond to sea level rise in the country.

Analyzing the Impacts of Sea Level Rise 
Investigations conducted in Sri Lanka have revealed that climate change will result in changes to critical forcing parameters of the coastal zone which would affect the physical condition of the shoreline. Rising sea levels, change in wave patterns arising from changes in wind pattern and water depth, increased rainfall and the occurrence of extreme events more frequently, are some of these. Sea level rise on its own would lead to several issues:      

        (i)  Inundation and displacement of low lying coastal areas and wetlands
       (ii)  Coastal erosion and degradation of shorelines
       (iii) Salinisation of estuaries and freshwater aquifers, and
       (iv) Changes to and migration of coastal eco-systems and habitats.

Assessing Risk for Sea Level Rise in the Coastal Zone
In order to develop a strategic approach towards planning and management of the impacts of this sea level rise, it is necessary to conduct a detailed risk assessment. This assessment should be done within a broad framework for multi-hazard coastal risk assessment framework. The risk assessment will comprise hazard, vulnerability, and capacity assessments. The superimposition of these components will lead to an overall risk assessment.
 

Hazard Assessment
For the hazard assessment component of the risk assessment, the impact on the coastal zone for three credible scenarios should be assessed. These scenarios will cover low, medium, and high states of sea level rise which can be developed with due consideration to existing sea level data along the coast and global predictions for the region. The primary impacts to be assessed are inundation and forecasts on increases in coastal erosion.

In the longer term, an assessment should also be done on the impact of global climate change on the wind patterns and the resulting impact on coastal erosion. The analysis could also accommodate the projected sea level rise. This assessment has to be achieved by using numerical models.

Vulnerability Assessment
Vulnerability represents the proneness of society, infrastructure, and natural resources to the impact of hazards. Critical parameters to be incorporated are identified under the six broad categories of human, physical, environment, socio-economic, functional and administrative.  In this context, it is necessary to prepare a Vulnerability Database for the coastal zone, which will enable an assessment of vulnerability to sea level rise along the coastal area of the country and estimate the economic cost for different scenarios.

Capacity Assessment
Capacity assessment is carried out to assess the ability of society to respond to the impacts of sea level rises and to also assess whether critical infrastructure would be able to withstand potential impacts. The ability of those engaged in low lying agriculture to move into other types of agriculture or trade in the event that their land cannot be protected, is a typical example. Another example is the relocation of fresh water intakes of heavily populated urban cities which are highly vulnerable to sea level rise.

Risk Assessment
Risk assessment can be achieved by the superimposition of the hazard, vulnerability, and capacity assessments and  can be achieved through a number of methods. Scenario-based approaches for hazards are frequently used, together with weighted methods for vulnerability. Of course, such methods must be developed in consultation with all stakeholders.

Modelling and Geo-information
The success of assessing risk will depend heavily on the use of reliable mathematical models for simulating the physical processes and the availability of geo-information. Good quality bathymetric and topographical data are essential for successful implementation of a risk assessment study. The vulnerability data base will comprise a wide range of relevant information. It is important that risk assessment is a dynamic process which has to be regularly upgraded. Therefore, data acquisition, storage, and management are of vital importance.

Proposed Actions and Investigation for the Coastal Zone
Based on risk assessment, it is possible to identify a series of measures to mitigate the impact of sea level rise. Arising from preliminary investigative studies undertaken along the coastal zone of Sri Lanka, some of the actions identified are listed below. These actions would be refined after the completion of risk assessment studies.

Inundation 
  • Incorporate climate change concerns in town and country planning and wetland conservation programmes.
Salt water intrusion 
  • Assess the increase in salt water intrusion in important water bodies. 
  • Evaluate engineering interventions needed to counter threat based on the potential impact on agriculture.
Fresh water intakes
  • Review the performance of existing intakes taking sea level rise into account.
  • Design new water intakes giving due consideration to climate change impacts.
Groundwater
  • Prepare groundwater extraction regulation policy. 
  • Introduce monitoring systems for groundwater extraction and water quality assessment in vulnerable areas.
Irrigation and Low lying Agriculture
  • Study impact on existing irrigation structures.
  • Introduce salinity tolerant varieties of crops, alternative land use or engineering interventions to maintain the existing regime.
Fishery Industry
  • Conduct sectoral assessment on climate change impacts on fishery development including fishery harbours, fishery settlements and sustainable use of fishery resource as a basis for long term planning.

Sea defence structure, near-shore infrastructure and land reclamation

  • Assess vulnerability and prepare plans for improvement as well as plans for emergency response/contingency.
  • Accommodate sea level rise in the design of new coastal structures.
  • Screen near-shore reclamation against sea level rise impact.

Incorporating Sea Level Rise and Coastal Zone Management
Coastal zone management involves management and decision-making regarding activities of the coastal zone including physical measures for coastal and flood protection and development works.  It has been identified that the three principal objectives of coastal zone management related to sea level rise are to:

              1. Avoid development in areas that are vulnerable to inundation.
              2. Ensure the continued function of critical natural systems.
              3. Protect human lives, essential properties, and economic activities against the adverse impacts of the sea.
In this respect, the following recommendations are made with respect to the management of the coastal zone:
  • Prepare set back limits to take account of sea level rise.
  • Delineate critical areas and prepare special area management plans.
  • Formulate coastal database incorporating information on hazards and vulnerability for implementing integrated coastal area management.
  • Incorporate greater consideration of climate change impacts in the next revision of the Coastal Zone Management Plan (CZMP).


Conclusion

Almost all the possible responses to sea level rise are best addressed within a broader context of coastal zone planning and management. Responses to climate change must be seen as a part of a broader coastal management policy which incorporates non-climatic issues.  If considered in isolation, the effectiveness of such responses would be reduced mainly due to incompatible policies and/or actions taken by other coastal sectors. Many responses to sea level rise are very similar to those required to address existing coastal zone management problems, therefore, there is a clear need for integrating the planning of sea level rise with coastal zone management practices. 

   Prof. S.S.L.Hettiarachchi

  Prof.  S. P. Samarawickrama
                                                    
                                                                          
Professor S.S.L.Hettiarachchi and Professor S.P.Samarawickrama are Professors of Civil Engineering at the University of Moratuwa, Sri Lanka. They both obtained their PhDs from Imperial College, London. Professor Hettiarachchi specialized in Coastal Structures and Professor Samarawickrama in Modeling of Coastal Waters. Both of them have jointly conducted research on impacts of episodic and chronic hazards in coastal regions, including the impact of sea level rise. They have contributed to national documents submitted to the UNFCC by the Sri Lankan government.

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