FLOOD MODELLING OF KALU-GANGA RIVER BASIN H. K. Nandalal Department of Civil Engineering University of Peradeniya Peradeniya Sri Lanka.

FLOOD MODELLING OF KALU-GANGA RIVER BASIN

H. K. NandalalDepartment of Civil Engineering

University of PeradeniyaPeradeniyaSri Lanka

2

Introduction

Problems related to flooding have greatly increased over recent decades because of

population growth development of extensive infrastructures in close proximity to rivers

It is importance to find solutions byutilizing modern technology like Geographic Information Systems (GIS), Remote Sensing (RS) and flood modeling

3

Outline of the Presentation

Study areaData usedSoftware usedApplication of Software

HEC-HMSHEC-RASENVI

4

Study Area

Kalu-Ganga river basin in Sri Lanka

Total catchment area is 2719 km2 Entire basin lies within the wet

zone. Average annual runoff is around

7600 MCM. Catchment experiences average

annual rainfall of 4000 mm.

5

Study Area

Study concentrates on the lower reaches of the river Area of interest is nearly 500 km2 This includes 5 Divisional Administrative Divisions (DSD)

6

Data Used

LIDAR DATAContour Data

TIN Model of the Study area

Data used

8

Data used

Locations of rainfall and discharge gauging stations

Raw Images (Dry Date, 03 March,2008) ALOS – PALSAR (HH)

Raw Images (Wet Date, 03 June,2008) ALOS – PALSAR(HH)

Data used

Satellite images

Data Collection and Data-basing…

Data used

Rainfall –Runoff Modeling

Application of HEC-HMS

Basin model developed using HEC-GeoHMS

Application of HEC-HMS

Results of the verification runs to compare the simulated flows and the observed flows of the calibrated HEC-HMS model

Application of HEC-HMS

Flood Modeling

Application of HEC-RAS

Geometric Data: HEC-GeoRAS export

Stream C/L River banks Flow paths

Application of HEC-RAS

Discharge data obtained from HEC-HMS

Elagawa

Mawakoya

Kuda GangaJunction Kuda Ganga/Kalu Ganga

Junction Mawakoya/Kalu Ganga

Flow (m3/s) data at\Return Period 10yr 20yr 50yr 100yr

Elagawa 1062.6 1319.7 1798.1 2605.5

Junction KudaGanga/ Kalu Ganga 1455.7 1836.9 2524.4 3743.3

Mawak Oya 97.5 122.2 174.4 245.5

Junction Mawak Oya/Kalu Ganga 1079.5 1340.5 1828.5 2647.7

Kuda Ganga 414.4 555.3 817.1 1260.7

Application of HEC-RAS

HEC-RAS output

Application of HEC-RAS

HEC-RAS output

Application of HEC-RAS

Flood Hazard Maps from HEC-RAS

Application of HEC-RAS

Raw Images (Dry Date, 03 March,2008) ALOS – PALSAR (HH)

Raw Images (Wet Date, 03 June,2008) ALOS – PALSAR(HH)

Verification of model result by satellite data

Mask(Difference dB image Wet - Dry)

Band Math Image (WET-DRY)

22

Flood extent resulted by satellite data

Comparison of the Flood extent derived from HEC-RAS model and Satellite image

Final Flood Hazard Maps

Thank you for your patience.Questions?