development of a gis-based landslide and flood risk model for the caribbean
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
Development of a GIS-based Landslide and Flood Risk Model for the Caribbean
ByJacob 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 IndiesSt. Augustine
Trinidad
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.
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
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
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)
Landslide and Flood Risk MappingObjective
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
Conceptual Design
Areal Population Density
Landslide Susceptibility
Population Risk to Landslide
Risk = Susceptibility + vulnerability (Population, Buildings)
Areal Buildings Density
Buildings Risk to Landslide
Buildings & Population Risk to Landslide
Inputs
Results
Landslide Susceptibility
Instability Factors
• Tectonic Features • Lithological Formation• Slope Angle • Road Network • Drainage Network • Land Use • Rainfall
Cartographic Model - Landslide
Ranking Weighting
Landslide Factor RankingInstability Factors
Classification Susceptibility Level
Rank
Road Network Proximity (m)
0-100m Very High 5
101-200m High 4
201-300m High 3
301-400m Moderate 3
401-500m Low 2
501-600m Low 2
>600m Very Low 1
Landslide Factor Weighting: Scenario E
Instability FactorsScenario E
%
Tectonic Features 2 0.20
Lithological Formation 2 0.20
Slope Angle 2 0.20
Land Use 1 0.10
Drainage Network 1 0.10
Road Network 1 0.10
Rainfall 1 0.10Total 10 1
Landslide Susceptibility MapSummation of land areas in each susceptibility class
Classes COUNT Area by cell Area (ha) % of total
Very Low 6159,360 615936,000
61,594 12.93
Low 15534,674 1553467,400
155,347 32.62
Moderate 14014,869 1401486,900
140,149 29.42
High 8397,885 839788,500
83,979 17.63
Very High 3522,375 352237,500
35,224 7.40
Total 4762916,300
476,292 100.00
Population Density Classification Scheme
Population Density by ED per hectares Vulnerability level0 - 19 Very Low19 - 76 Low76 - 191 Moderate191 - 1,032 High1,032 - 4,874 Very High
Building Density Classification Scheme
Building Density By ED per hectares Vulnerability level0 - 8 Very Low8.0 - 20 Low20 - 51 Moderate51 - 135 High135 - 441 Very High
Vulnerability
Population Vulnerability Class
Building Vulnerability Class
Very Low Low Moderate High Very High
1 2 3 4 5
Very low 1 2 3 4 5 6
Low 2 3 4 5 6 7
Moderate 3 4 5 6 7 8
High 4 5 6 7 8 9
Very High 5 6 7 8 9 10Risk Level Risk Value
Very low <3
Low 3-5
Moderate 6
High 7
Very High > 7
Single-Risk (Population) MapSingle-Risk (Buildings) MapMulti-Risk (Buildings and population) Map
Results: Landslide Risk Maps
Landslide Population Risk Assessment
Single Risk Classification Scheme
Vulnerability Class
Susceptibility Class
Very Low Low Moderate High Very High
1 2 3 4 5
Very low 1 2 3 4 5 6
Low 2 3 4 5 6 7
Moderate 3 4 5 6 7 8
High 4 5 6 7 8 9
Very High 5 6 7 8 9 10Risk Level Risk Value
Very low < 3
Low 3-5
Moderate 6
High 7
Very High > 7
Landslide Population Risk (Sum of Land Area under each risk level)
Risk Level Number of cells Area (m2) Area (HA) % of Trinidad
urban land mass
Very Low 32,352 3,235,200 323.52 0.61%
Low 523,056 52,305,600 5,230.56 9.84%
Moderate 1,188,482 118,848,200 11,884.82 22.36%
High 1,485,898 148,589,800 14,858.98 27.96%
Very High 2,084,492 208,449,200 20,844.92 39.22%
Landslide Building Risk Assessment
Landslide Building Risk Assessment(Sum of Built-up Area under each risk level)
Risk Level Number of cells Area (m2) Area (HA) % of Trinidad urban
land mass
Very Low 648,679 64,867,900 6,486 12.2%
Low 1,271,283 127,128,300 12,712 23.9%
Moderate 1,513,640 151,364,000 15,136 28.5%
High 1,249,585 124,958,500 12,495 23.5%
Very High 631,093 63,109,300 6,310 11.9%
Landslide Multi-Risk Assessment: Building and Population
Multi-Risk Classification Scheme
Vulnerability Class
Susceptibility Class
Very Low
Low Moderate High Very High
1 2 3 4 5
Very low 1 3 4 5 6 7 1
Low 2 5 6 7 8 9 2
Moderate 3 7 8 9 10 11 3
High 4 9 10 11 12 13 4
Very High 5 11 12 13 14 15 5Multi-Risk Level Risk Value
Very low < 6
Low 6-7
Moderate 8-9
High 10-11
Very High > 12
Landslide Multi (Building & Population) Risk Assessment(Sum of Land Area under each risk level)
Risk Level Number of cells Area (m2) Area (HA) % of Trinidad
urban land mass
Very Low 505,088 50,508,800 5,050.88 9.50%
Low 919,685 91,968,500 9,196.85 17.31%
Moderate 1,197,265 119,726,500 11,972.65 22.53%
High 1,201,305 120,130,500 12,013.05 22.61%
Very High 1,490,937 149,093,700 14,909.37 28.06%
Flood Risk MappingObjective
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
Conceptual Design
Areal Population Density
Flood Susceptibility
Population Risk to Flooding
Risk = Hazard Susceptibility + Vulnerability (Population, Buildings)
Areal Buildings Density
Buildings Risk to Flooding
Buildings & Population Risk to Flooding
Inputs
Results
Factor Modelling - Flooding
Flood Factors• Rainfall (mm) • Slope (%) • Land Use • Drainage density • Road (% each watershed) • Elevation (m)
Cartographic Model - FloodRanking Weighting
Flood Susceptibility MapSummation of land areas in each susceptibility class
Classes COUNT Area by cell Area (ha) % of total
Very Low 2,327,910 232,791,000
23,279 4.86
Low 9,959,195 995,919,500
99,592 20.79
Moderate 16,847,280
1,684,728,000
168,473 35.16
High 13,471,559
1,347,155,900
134,716 28.12
Very High 5,304,962 530,496,200
53,050 11.07
Total
4,791,090,600
479,109 100.00
Population Vulnerability Classification Scheme
Population Density By ED per hectares Vulnerability level0 - 19 Very Low19 - 76 Low76 - 191 Moderate191 - 1,032 High1,032 - 4,874 Very High
Building Vulnerability Classification Scheme
Building Density By ED per hectares Vulnerability level0 - 8 Very Low8.0 - 20 Low20 - 51 Moderate51 - 135 High135 - 441 Very High
Single-Risk (Population) MapSingle-Risk (Buildings) MapMulti-Risk (Buildings and population) Map
Results: flood risk maps
Flood Population Risk Assessment
Single Risk Classification Scheme
Population Vulnerability Class
Susceptibility Class
Very Low Low Moderate High Very High
1 2 3 4 5
Very low 1 2 3 4 5 6
Low 2 3 4 5 6 7
Moderate 3 4 5 6 7 8
High 4 5 6 7 8 9
Very High 5 6 7 8 9 10Risk Level Risk Class
Very low < 4
Low 4-5
Moderate 6
High 7
Very High > 7
Flood Population Risk (Sum of Land Area under each risk level)
Risk Level Number of cells Area (m2) Area (HA) % of Trinidad urban
land mass
Very Low 1,194,834
119,483,400
11,948 22.48%
Low 1,687,858
168,785,800
16,878 31.76%
Moderate 1,644,578
164,457,800
16,445 30.95%
High 696,494
69,649,400
6,965 13.11%
Very High 125,510
12,551,000
1,255 2.36%
Flood Building Risk Assessment
Flood Building Risk Assessment(Sum of Land Area under each risk level)
Risk Level Number of cells Area (m2) Area (HA) % of Trinidad
urban land mass
Very Low
1,405,680
140,568,000
14,057 26.45%
Low
1,716,196
171,619,600
17,162 32.29%
Moderate
1,496,094
149,609,400
14,961 28.15%
High
625,967
62,596,700
6,260 11.78%
Very High
105,337
10,533,700
1,053 1.98%
Flood Multi-Risk Assessment: Building and Population
Multi-Risk Classification Scheme
Vulnerability Class
Susceptibility Class
Very Low
Low Moderate High Very High
1 2 3 4 5
Very low 1 3 4 5 6 7 1
Low 2 5 6 7 8 9 2
Moderate 3 7 8 9 10 11 3
High 4 9 10 11 12 13 4
Very High 5 11 12 13 14 15 5Multi-Risk Level Risk Value
Very low < 6
Low 6-7
Moderate 8-9
High 10-11
Very High > 12
Flood Multi (Building & Population) Risk Assessment(Sum of Land Area under each risk level)
Risk Level Number of cells Area (m2) Area (HA) % of Trinidad
urban land mass
Very Low
925,747
92,574,700
9,257 17.42%
Low
1,467,641
146,764,100
14,676 27.62%
Moderate
1,334,220
133,422,000
13,342 25.11%
High
1,402,912
140,291,200
14,029 26.40%
Very High
218,754
21,875,400
2,188 4.12%
Uses• Development control and planning • Disaster mitigation planning • Disaster management • Policy formulation • Law reforms • Site analysis • Review of insurance premium
Users• Physical Planning Offices • Non-Governmental Organizations • Environmental Agencies • Works Departments • Utility Companies • Insurance Agencies • National Disaster Offices • Security and Protective Services • Lending Agencies • Meteorology and Hydrology Departments • Educational Institutions • Land Developers • General Public • Foreign Investors
Questions &Comments