Development of a GIS-based Landslide and Flood Risk Model for the Caribbean

1. Development of a GIS-based Landslide and Flood Risk Model for the Caribbean By Jacob Opadeyi PhD, Gabrielle Thongs MSc, Leah Fouchong BSc, Roxann Smith BSc, Desiree Joseph Bsc, Shelly Bradshaw BSc Department of Geomatics Engineering and Land Management The University of the West Indies St. Augustine Trinidad

2. Background • The location of the Trinidad in the extreme south of the Caribbean means the country experiences a tropical marine climate. • Floods and landslides are annual events associated with the rainy season in Trinidad and Tobago. • Flooding and landslides are the most common and significant localized hazard.

3. To the end of William Road, El Socorro South, yesterday (May 27th 2010). Around 6.30 am the Caroni River, which runs to the back of El Socorro South burst its bank due to heavy rainfall. As a result hundreds of acres of crops were submerged in water. Trinidad Guardian 28 May 2010

4. Two people are dead and one family is hoping that five of its members who are in critical condition live, after a landslide struck the village of Delaford on Tobago's west end. Caribbean Net News  Tuesday, November 16, 2004 Geraldo Greene, a 76-year old pensioner suffered a cruel death on Friday when a landslide destroyed part of his Santa Cruz home killing him in the process. Trinidad Express - Aug 6, 2001

5. Background • Trinidad and Tobago faces a number of natural disaster issues • Vulnerability assessment and risk mapping are the important first steps for any initiative for disaster reduction. • A risk assessment is not only to find out where risk related problems are located, but also to quantitatively or qualitatively determine the significance of risks (Smith 2001, Greiving et al 2006)

6. Landslide and Flood Risk Mapping Objective To evaluate and rank the risk level to landslide of the resident population and the physical assets (buildings) of Trinidad. Input data • Landslide susceptibility maps • Population spatial distribution • Building spatial distribution

7. Conceptual Design Risk = Susceptibility + vulnerability (Population, Buildings) Landslide Susceptibility Inputs Areal Buildings Density Areal Population Density Buildings Risk to Landslide Population Risk to Landslide Results Buildings & Population Risk to Landslide

8. Landslide Susceptibility

9. Instability Factors • Tectonic Features • Lithological Formation • Slope Angle • Road Network • Drainage Network • Land Use • Rainfall

10. Cartographic Model - Landslide Ranking Weighting

11. Landslide Factor Ranking

12. Landslide Factor Weighting: Scenario E

14. Landslide Susceptibility MapSummation of land areas in each susceptibility class

18. Population Density Classification Scheme

23. Building Density Classification Scheme

24. Vulnerability

26. Results: Landslide Risk Maps Single-Risk (Population) Map Single-Risk (Buildings) Map Multi-Risk (Buildings and population) Map

27. Landslide Population Risk Assessment

28. Single Risk Classification Scheme

31. Landslide Building Risk Assessment

34. Landslide Multi-Risk Assessment: Building and Population

35. Multi-Risk Classification Scheme

39. Flood Risk Mapping Objective To evaluate and rank the risk level to flooding of the resident population and the physical assets (buildings) of Trinidad Input data • Flood susceptibility Map • Population spatial distribution • Building spatial distribution

40. Conceptual Design Risk = Hazard Susceptibility + Vulnerability (Population, Buildings) Flood Susceptibility Inputs Areal Buildings Density Areal Population Density Buildings Risk to Flooding Population Risk to Flooding Results Buildings & Population Risk to Flooding

41. Factor Modelling - Flooding

42. Flood Factors • Rainfall  (mm) • Slope (%) • Land Use • Drainage density • Road  (% each watershed) • Elevation (m)

43. Cartographic Model - Flood Weighting Ranking

45. Flood Susceptibility MapSummation of land areas in each susceptibility class

47. Population Vulnerability Classification Scheme

49. Building Vulnerability Classification Scheme