Capacity Building in Applications ofGeoinformatics in Flood Hazard Mapping

byManzul Hazarika Ph.D.
Geoinformatics Center (GIC)
Asian Institute of Technology (AIT), Bangkok
E-mail: manzul@ait.ac.thCapacity Building Projects in Disasters
Capacity building projects are being sponsored by the Japan Aerospace
Exploration Agency (JAXA) in developing countries.

Projects:
 Flood– 5 Projects (Bangladesh, Cambodia, China, Laos & Nepal)

 Landside – 3 Projects (Philippines, Sri Lanka & Vietnam)
 Drought – 1 Project (Philippines)

Activities:
1. Workshop and Training in AIT– Aug/Sep, 2006
2. Field Visit – Nov/Dec, 2006
3. Data Analysis and Report Writing in AIT– Jan/Feb, 2007

Flood Projects
Sl.
No.

Country

1

Bangladesh Flood Forecasting & Warning Center (FFWC)

Organizations

Local Government Engineering Dept. (LGED)
Bangladesh Disaster Preparedness Center (BDPC)
2

Cambodia

Geography Department, Ministry of Land Administration
Urban, Planning and Construction (MLUPC)
Hydrology and Water River Works Dept., Ministry of Water Res.
and Meteorology (MOWRAM)

3

China PR

Beijing Normal University

4

Lao PDR

Environmental Research Institute (ERI), Science Technology andEnvironment Agency
Department of Meteorology and Hydrology (DMH)

5NepalDepartment of Water Induced Disaster Prevention (DWIDP)
Survey Department
Department of Hydrology and Meteorology (DHM)Bangladesh: Flood Mapping by Integrating RS Data& MIKE 11 Model

Munshiganj

China: Flood Risk Assessment using RS andHydrologic model in the Xiang Jiang River

Laos: Application of RS-GIS for Flood Extent
Study in Savannakhet ProvinceCambodia
A Detail Example for Flood
Hazard MappingStudy Area

Study area covers 3 provinces (Kompong Cham, Prey
Veng, Kandal and Phnom Penh), 26 districts, 305
communes with population 245,086 persons.

Problem StatementA number of settlements usually in both banks of the Mekong
river are flooded during the rainy season (August-November)Major Floods in Recent Years
Year 2000••••

On 28 Aug., 2000
1139 dead, 6,574,000 displaced
208200 sq. km area flooded
Property Damage 78.2 Million US$Year 2006•••

From 10 Aug. to 1 Nov., 2006 (84 days)
68 dead, 33,000 displaced
143,300 sq. km area flooded

2000 Flood (Dartmouth Flood Observatory)

http://www.dartmouth.edu/~floods/Archives

2006 Flood (Dartmouth Flood Observatory)

Main Objectives of the Study• To integrate a flood simulation model and remotely sensed
data with the available topographic and socio economic data
in a GIS environment• To validate the model by comparing the flood inundation areaand depth with the available flood maps and remote sensing
image.
• Preparing hazard maps using depth map and the socioeconomic dataAvailable Satellite Data of Study Area

Landsat 03-Jan-2005

Aster 06-Jan-2003

Available Satellite Data of Study Area

ALOS Sensor AVNIR-2
Level-1B2 Date:27 Aug, 06

Radarsat 23 & 25 Sep. and 05 Oct.
2000, Band-C Source :LIDER Project,MRC Secretariat

Available hydrological data for study• Daily average river discharge data (m³/s) (KampongCham and Chroui Changvar) (from 1991 to 2002)• Water surface heights (MSL) (Kampong Cham andChroui Changvar) (1991 to 2002)• Manning’s co-efficient of Roughness for the River bed
and the flood plain derived from the landuse map.

Available ancillary data for study• Census data
• Socio-Economic data (CELA Program, UNDP)• Spot heights of the flood plain/river bed• Topographic maps (1:50,000) (Geography Department)• Administrative and other vector mapsHydrological stations

Hydrological Data: Peak Discharge
Available data From (1991 to 2002)

Source: Dept. of hydrology andriver works, Ministry Of Water
Resources and Meteorology,Cambodia

Landuse Map
Class

Manning’s ValueAgricultural Lands



Forest Covers
Grasslands
Shrub Lands
Soils and Rocks
Urban Built Up area
Water Features

0.04
0.05
0.03
0.035
0.038
0.160
0.025






Methodology
Fieldwork and Data
Acquisition Phase

Spatial Data

Spot heights
GPS observed Heights
Topographic maps
Landuse maps
Landsat ETM
Aster Data

Hydrological Data

Discharge data
Rainfall Data
Cross sectional data
Manning’s Coefficient

Physical environment andlandscape preparation

Modelling Phase
DEM created
From spatial data

Geometric
data creation

HEC-RAS
ModelDischarge
Manning’sCoefficientRiver Cross-section

Hydrological
Data Creation

HEC-RAS
Model

Editinggeometric data
And model
Performing

Modelvisualization inGIS
environment

Methodology contd.
Validation evaluation and hazard assessment phase
Comparison of model
result with flood map
from a reliable source
Like Dartmouth flood
observatory report Ora Base Map

Model result
From HEC-RAS

Model result
From Mike-11

Accuracy checkFlood Model result
HEC-RAS
Reclassification+Landuse map
From Landsat
ETM,
Reclassification+Population Density
Map
Reclassification

Weighted Map Calculation
Final Hazard Map

Field Survey
Right Bank: 95.15Km
Left Bank: 43.62 Km
PP-Kg.Cham:

During Field Survey

2000 Flood – RADARSAT Image

2000 Flood – Overlaying Mike-11 Model
Results

2000 Flood – Overlaying HEC-RAS Model
Results

Cross Section at Kampong Cham

Cross section
AtKampong Cham
Max. Depth=30 m

Overflowing Banks (Left)

Overflowing Banks (Right)

Capital Phnom Penh Was Not Flooded

Highway No.-5
Acts as a DykeShown in thecross sections

Flood Affected Villages
Village Affected by flood and non-flood

No. village

2000

1693

1500
1076
1000
500
0FloodedNon flooded

Population and household
affected and no affected
1,500,000

1214067 1211019

1,000,000
500,000
0267842244626

Total Both Sexes

Total Households

flooded1214067267842

non-flooded

1211019244626

Area For Flood Hazard MappingWeighted Population Map+Population per commune X Weighted Landuse
Total Weight

Weighted Population per pixel=Enlarged Weighted Population Map

Flood Depth From HEC-RAS ModelReclassified Landuse Map

Flood Depth Map

Final Hazard Map

Summary for CambodiaHazard

Population % of total
3Rank
Agriculture Build Up Agriculture Build Up affected (10 ) population
Low
305
396
0.09
0.65
104
4.31
Medium
2387
3400
0.70
6.62
394
16.25
High/V.High
High
12646
12734
3.70
21.03
720
29.71
Land Affected, ha% of total land

• The Extent of the flood depth from HEC-RAS is comparablewith the flood map derived from RADRASAT data
• The water depth in the river from the model is comparablewith the recorded water depth at the two locations atKampong Cham and Chroy Changvar.
• The flood depth from the model is comparable with theobserved depth in the flood plain.

Nepal: Flood forecasting and early warning
system in Bagmati flood plain
26º30'-28º00' N,
85º30'-86 º 00' E

Methodology
Satellite image

Rainfall data

(1. TRMM & 2. Rain gauge data)

1. DEM
2. Flood map
3. Landuse map

Hydrologicalmodel(1. HEC HMS and 2. Statistical)

Topographical
Data

Flood hydrographHydraulic model(HEC RAS)

Flood maps

Comparison &Improvement

Community
surveyRating curve
Flood maps forDiff. Return periods

Flood hazard
Direct flood
Flood maps formaps
damage assessment Diff. Water levels
Populationdata

Flood risk maps

Flood Early
War ning System

Data Available• Satellite imagery• Hydrological data

– Aster– Landsat– Rainfall data
– Discharge data

• Vector data

• Ancillary data

– Topographic data
– DEM
– Landuse data

– Socio-economic data
– Census data

Regression Analysis Approach of Peak
Discharge Prediction
Assumption and Steps for discharge prediction• TRMM rainfall data is used
• Time of Concentration = max. 24 hours• Partially or fully covered 3B42RT grids = 15
• Contributing Grids at Gauging Station = 11

TRMM Grids in the Study Area

Regression Analysis Approach of Extreme
Discharge Prediction (Contd.)• Grid rainfall data are weighted according to theiraerial coverage• Grids having equal time of concentration are grouped
together (called Block)• Discharge (Q) = f (weighted time series of 3-hourlyrainfall)Regression Analysis Approach of Extreme
Discharge Prediction (Contd.)
Test Datasets• TRMM 3-hourly rainfall data covering June to September 2004
• Daily discharge data of the same period (Dependent Variable)
Validation Data
• 2005 Monsoon (June to September)• Predicted Variable is daily discharge data of Monsoon 2005

Flood maps
Input Discharge
Return Period

Discharge

2 year3750

5 year6150

10 year7750

20 year9250

50 year11250

100 year

12700

Inundated area
Return period

Area inundated% area inundated

2 year

363.4

36.9

5 year403.9

41

10 year

422.9

42.9

20 year

437.7

44.5

50 year

454.8

46.2

100 year

465.6

47.3

Damage function analysis - 1

Depth vs. Damage: Flood duration (B.M)

Depth vs. Damage: Building Age (B.M)

Depth vs. Damage: Crop Damage

Summary for Nepal•
••

•

•

Diurnal variability of TRMM rainfall field is well captured
TRMM rainfall field is more associated with the average
rainfall field rather than a point rainfall
Weighted time series 3-hourly TRMM data is well predictthe peak discharge which can be directly used for flood
forecasting.
The flood maps prepared for six return periods of 2, 5,
10, 20, 50 & 100yrs showed inundation area ranged from363 – 465 sq. km. (37-47% of the total area of the twodistricts)
Flood loss functions were generated for structural
damage of residential and commercial buildings

Acknowledgements
Cambodia
1. Yin Savuth
2. Ro Narith
3. Noun Kunthea

Ministry of Water Resources and Meteorology
Ministry of Land Management, Urban,
Planning and Construction
RFMMC, Mekong River Commission

Nepal
Sudarshan Karki

Survey Department

Rishi Ram Sharma Dept of Hydro. and Met.
Rajan Shrestha

Dept of Water Induced Disaster Prevention

Geoinformatics Center/AIT
Mr. Tanka KafleThank you for your kind attention