Integration of RS, GIS and MIKE 11 Hydrodynamic Modeling for Flood Early Warning: A case study of the Langat river basin Malaysia
The second part of the study involves the compilation of hydrological data to develop a GIS database on ArcVeiw GIS platform. The variously defined hydrological data are as listed in the illustration of figure 2. The GIS provides the essentials for digital elevation model (DEM), river and floodplain surface geometry. It also provides the tools for visual interpretation and evaluation of flood distribution and inundation maps. The MIKE 11 hydrodynamic model combines advance time series simulation and automated water level discharge and rainfall-runoff process. MIKE 11 is calibrated based on expect pre-flood rainfall data compute from the QPF and also historical time series of available hydrological data of rainfall. Rainfall runoff is computed based on the NAM distributed model.
Results and Discussion The NIR and IR channels 3, 4, and 5 of the data were processed for temperature and brightness. In an infrared (IR) image cold clouds are high clouds, so the colors typically highlight the colder regions Mid height clouds with TB below 235k were identified as cumulonimbus cloud with a high probability to precipitate. Lower probabilities were associated to warm but bright stratus cloud and thin cirrus cloud that were cold but dull. Rainfall is estimated based on the assumption that every cloud pixel has a constant unit rain-rate of 3mmh-1, which is appropriate for tropical precipitation over 2.5o x 2.5o areas around the equator. The study area shows warm but bright non-precipitating stratus cloud. Object orient classification technique is use for cloud classification based on cloud type, probability to precipitate and height, figure 3 shows various cloud type identified on the AVHRR data. Although the coarse resolution of 1.1km of AVHRR data did not allow for high-level classification, the object orient classification proved effective for the cloud type identification due to the input of shape, texture and spectral information in the classification process through the multi dimensional input object functions. The processing for QPF is still preliminary and thus results are indicative and were not used for this study’s hydrodynamic simulation.  Fig 3 Cloud Type Identification and Classification The Langat river basin is divided into sub-basins to enable an easy computation of runoff for each watershed. Hydrodynamic simulation is performed for the Denkil sub-basin of Langat for the for the flood record of the monsoon 2000. The simulation period is 12 day from Sept 27 to Oct 8, this period saw high level of water in the Denkil branch of Langat river causing floods. A simulation profile of water level is shown on Fig 4 (a) with water level exceeding river capacity at the left end of the profile. Fig 4 (b) shows the unit time series graph for discharge and water level for this period.  Fig. 4 Dekil river simulation, DEM & Flood inundation Map |