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The flood maps generated for the city of Phnom Penh were prepared as part of my MSc research to assess the applicability of using simple flood modelling techniques in the South East Asian cities with a range of available topography data (DEM). While the simulation of the 2-dimensional flood model was carefully carried out, and maps were carefully processed, no verification of the resulting inundation extents was made so far. These maps should be considered part of the demonstration of this interactive visualisation tool and the flood mapping methodology.
Note: Screen capture of map used the below settings on July 12, 2012. Website links to the live map.
- You will be able to pan and zoom around and use a range of background map layers.
- You can also switch between predicted flood extents generated using a range of DEM inputs (30m SRTM, 90m ASTER, 100m DTM and 7m DTM which produces much better results).
- You can also view the depicted flood areas resulted from different rainfall events.
The flood extents were generated using ISIS-FAST. It is an innovative flood inundation modelling tool designed to allow quick assessment of flooding using simplified hydraulics. It provides results in seconds or minutes as opposed to hours or days, which is up to 1,000 times faster than traditional two-dimensional models.
Click on the following link for a detailed information about ISIS-FAST.
The accuracy of the model results depends mainly on the degree of accuracy of the topography (DEM) data that were used in the flood simulation. It should also be noted that method employed is very simple and has not been calibrated; and other factors like infiltration, drainage, and the likes were not incorporated in the model.
The SRTM type of digital elevation model (DEM) was generated by advanced remote sensing techniques through the use of radar satellite during the Shuttle Radar Topography Mission (SRTM) in February 2000. The method used to measure the digital topography of about 80% of the total Earth landmass is known as the synthetic aperture radar (SAR) interferometry. It was then that the first global high-quality DEM was achieved with a resolution of 3 arc sec (90m).
The Global Digital Elevation Model Version 2 (GDEM V2) was released on October 17, 2011 and is the world’s first three-dimensional terrain data that covers 99 percent of the Earth’s landmass. The digital topography data were generated based on enormous amount of image data captured by Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), a space-borne earth observing optical instrument. It has a spatial resolution of 30m which exceeds that of three-dimensional terrain data captured by SRTM (90m resolution).