cover image: Quick-Scan Runup Reduction through Coral Reef Restoration in the Seychelles

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Quick-Scan Runup Reduction through Coral Reef Restoration in the Seychelles

20 Nov 2020

Being a small island nation, Seychelles is highly exposed to natural hazards, especially coastal erosion, coastal flooding, flash flooding, and rock fall. In an effort to improve this understanding and explore potential sites for nature-based solutions – in the form coral reef restoration in particular – to reduce coastal flood risk, the World Bank and the GFDRR have financed a quick-scan analysis for three islands of the Seychelles (Mahé, La Digue, and Praslin) to identify candidate sites which have a high potential for the reduction of wave runup through coral reef restoration. This report, performed by Deltares, uses remote sensing and existing datasets to estimate key site parameters such as reef width, depth, roughness, and beach slope. Hydrodynamic forcing is assessed using wave and water level conditions. The reef morphology and hydrodynamic forcing is then used in the BEWARE system to estimate runup under a range of different scenarios, including reef roughness as a proxy for coral health. The report presents spatial maps of relative and absolute runup change for the three islands for various water levels and wave conditions, together with the digital data of the computed runup values. Intermediate data on the reef input parameters (reef width, reef slope, beach slope, and reef roughness) are also included.
environment disaster risk reduction sea level rise climate risk seychelles data quality hydrology industry natural disasters remote sensing water level water resources natural hazard open data standard deviation satellite imagery risk financing tropical cyclone linear regression probability distribution storm surge expected value independent variable regime shift quantitative data nature-based solutions health care services industry land and water financial impact data availability international agency climate analysis government institution wave breaker africa east financial response vulnerable countries recipient countries transportation,water, sanitation and waste management,public administration visual inspection flash flood document control new idea unique identifier local partner reasonable effort small island field measurements absolute reduction bathymetric survey time sery model result deep water recovery activity noncommercial purposes return period several steps coral reef restoration tidal water southern hemisphere calibration factor coral restoration steep gradient parameter value fish community supervised classification central government (central agencies),other water supply, sanitation and waste m wave condition coral health beach width surface elevation water depth total water lag effect coral reef conservation offshore islands end products estimation technique personal communication wave period uniform distribution wave length tropical area significant wave height train network fringing reef live coral bathymetric chart network construction disaster-prone country colour change prevailing wind coral rubble coral cover coastal site flood potential wave direction satellite image interpretation base case coastal flood risk incident wave

Authors

Deltares,Jongman,Brenden [WB editor],Van Zanten,Boris Ton [WB editor]

Disclosure Status
Disclosed
Doc Name
Quick-Scan Runup Reduction through Coral Reef Restoration in the Seychelles
Document Date
2020-11-01
Published in
United States of America
Rel Proj ID
SC-Disaster Risk Management Development Policy Loan With Cat Ddo -- P148861
Total Volume(s)
1
Unit Owning
N/A
Version Type
Final
Volume No
1

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