Keuwords: ACRS, Flood Prediction, DEM, SCS TR-55, GIS, Remote Sensing.
Abstract Flooding has been the most life and properties threatening disaster especially in a big
urbanized country like Kuala Lumpur. Changes of land-use pattern have been the major contributing
factor of effect. This paper will discussed on the study of flood problem using the Remote Sensing and
GIS technology for flood prediction in Klang Valley (Kuala Lumpur). Digital elevation Model (DEM)
was produced from interpolation of contour heights at interval of 20 meter from 1:50,000
topographical map. The river basin region was then delineate into smaller subwatershed which later
used in the hydrologic design modelling. Flood inundation are predicted using the Graphical Method
of Soil Conservation Service Technical Release 55 (SCS TR-55) model which defined the peak
discharge and Stage - discharge rating curve are use to correlate the predicted peak discharge with the
height of water level directly measure from the field at the concerned 4 river-gauge stations. The
calculation of peak discharge involves the calculation of Runoff Curve Number (CN) method that
relates to land use pattern of study area. Aspect of landuse pattern are derived from the SPOT-XS
image. Rainfall data are used as the input data.
1.0 Introduction
The Klang river basin is located towards the west coast of Peninsular Malaysia, in the central
part of Selangor State. The basin consist of most urbanized and still rapidly urbanizing regions
including the nation's Capital of Kuala Lumpur. Increase in urbanizing may result in increment of
sedimentation and pollution. Even though there's a lot of mitigation projects have been done, the
problem of flooding still remain as one of the most frequent and devastating natural hazards to this
area.
Flood is among the most common and widespread natural hazard phenomena causing billions
of dollars in damage each year. Changes in land use pattern especially development from the rural area
to the urban area have become one of the major cause. According to JICA(1989), there are two causes
of flooding that is depression-type monsoon storm and thunderstorm. The main focus of study is the
thunderstorm flooding also known as flash flood, that might cause more damages to the civilization.
Because of its high intensity, localized and short duration (3-5 hrs) characteristic flood event, it's study
become more important especially in flood forecasting. The localized occurrence of flooding aspect
makes it easier to locate the flood prone areas.
Remote sensing and GIS are used widely especially in the disaster related assessment because
there is a need for more timely and detail information of the location, area and extent of the damage
from a disaster to aid in response and recovery activities. Remotely sensed data are the most suitable
approach since site investigation become almost impossible to manage during flood event.
This paper will discussed on the use of DEM and the SPOT image data to derived the
parameter used in U.S. Soil Conservation Service Technical Release 55 (SCS TR55) hydrological
model in prediction of floods by determining river stage at the 4 chosen river station.
2.0 Digital Elevation Model
DEM can be created by collecting elevations and referencing them to the corresponding points
in the mapped area. Digital contour lines digitised from the topographic map is the main source of the
DEM generation. Two main steps followed in constructing DEM. The first step is converting contour
data containing elevation attribute into the point data. The second step will generates the surface from
the point data created in the first step. The triangulated irregular network (TIN) are applied in this
process. The topographical map of 1:50 000 scaled (1991) with 20m interval are used.
Information may be extracted in two ways, by visual analysis of graphic representation or by
quantitative analysis of digital elevation data. The DEM will provide automatic layers for perspective
viewing, slope analysis, terrain analysis, hydrography analysis and flood simulation.
3.0 Subwatershed Delineation
For the purpose of hydrologic design modelling, subdividing the watershed is often necessary.
As being described by Mc Cuen (1998), the boundary of a watershed is defined by all points that will
shed water to the outlet. Water will travel perpendicular to the elevation contour, which is the direction
that maximizes the slopes. In this method, DEM are used instead of using contour line.
To qualify the needs of Graphical Peak Discharge Method, the study area is delineated into
small homogenous subwatersheds (Figure1).
Figure 1: This Map Showing The Correspond Subwatershed and River Station in The Study Area.
4.0 Satellite Data Processing
Geometric Correction
The SPOT-XS image (April, 24 1998) was rectified to RSO grid projection using the ground
control point (GCP). The mathematical model used here is polynomial and 20 control points are
chosen from the topographical map of the study area for source of GCP using the user entered method.
Image Classification
The process of image classification was carried out to classify the landuse pattern at the
surrounding area of 4 stated river station. The supervised classification technique was used. The
training areas are localized and identified using the topographic map (1991) of Kuala Lumpur. The
homogenous area defined at the four river station are all the urbanized area with lots of parking lots
and residential areas with CN is 85.
