- 16th June 2017
- Posted by: Sabina Gubbin
- Category: Projects
Information about flood hazard and associated damages developed through the Strategic Flood Risk Assessment was deemed by the World Bank to provide a deeper understanding of the coastal management challenges faced by the Government of Suriname. The Coastal Resilience Assessment was developed to consider the effectiveness of natural, artificial, non-structural and hybrid interventions to mitigate natural hazards of erosion and coastal flooding.
A focus of the study was to develop a greater understanding of the role played by mangroves to provide coastal protection, and how their ecological benefits contributed to the social well-being of Suriname.
To consider holistic management of coastal hazards for the city of Paramaribo, including erosion and coastal flooding. This assessment has involved detailed collation and evaluation of in-country knowledge, to synthesise a strategic pathway for future coastal management.
The study aimed to investigate:
- Coastal flooding and erosion risks to Paramaribo
- The role that mangroves can play as part of a sustainable solution
- The wider benefits that mangrove solutions can provide
- The influence of human and natural processes on coastal resilience
Key objectives were to:
- Inform the development of a program of interventions, associated policies, and the investment plan required to address flood and erosion risks
- Provide tools necessary to investigate the cost-benefit of different coastal resilience options
Coastal flooding risk was quantified through combining in-country flood observations with regional high resolution data sets and global altimetry. Limitations of existing tidal predictions were highlighted, and the sensitivity to mean sea level rise was confirmed, with 0.2m sea level rise estimated to increase the incidence of flooding by a factor of 10x. The spatial extent of coastal flooding was characterised by hydrodynamic modelling.
The coastal change record was examined to assess evidence of a range of contributing factors. The most substantial factor identified was the naturally-occurring migration of massive mud-banks that move westward along the coast of Suriname. These cause cycles of shoreline erosion and accretion, with movement of about a kilometre over 30 years. In this setting, mangroves provide partial resistance during the erosive phase, and substantially contribute to sediment capture during the accretive phase. Consequently, the presence of a coastal fringe of mangroves is essential to coastal stability, while providing more moderate mitigation of coastal flood hazard.
Evaluation of coastal hazard mitigations highlighted that no single approach is expected to provide a solution for both erosion and inundation hazards. Economic analysis of capital cost, maintenance cost, land productivity, relocation costs and coastal degradation demonstrated the cost-benefit effect of spatially varying the position of flood mitigation works. The considerable uncertainty associated with economic analysis, including potential study bias, was recognised.
The Coastal Resilience Assessment highlighted that Suriname lies within a unique oceanographic, ecological and geomorphic setting. Understanding these processes is important because they drive the risk of flooding and erosion which in turn influence the practicality of possible interventions measures.
In particular, the muddy coastline of Suriname is highly dynamic and transient and any intervention implemented needs to consider the mechanics of the coastline and the fact that there are long-term cycles of coastal change in operation. Based on the influence of these cycles, the study has highlighted that a seawall at the coast is not a sustainable solution for Suriname.
What the Greater Paramaribo area requires is an integrated flood risk management strategy. This is likely to require some form of flood barrier, set back from the coastline by at least 1.5km, combined with a mix of natural, structural and non-structural interventions. Revision of land planning policies is required to economically support the use of flood defences, and institutional changes need to be introduced to enforce planning policy.
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