Digital Elevation Models and GIS for Watershed Modelling and Flood Prediction – A Case Study of Accra Ghana
Geographical Information Systems (GIS) and Digital Elevation Models (DEM) can be used to perform many geospatial and hydrological modelling including drainage and watershed delineation, flood prediction and physical development studies of urban and rural settlements. This paper explores the use of contour data and planimetric features extracted from topographic maps to derive digital elevation models (DEMs) for watershed delineation and flood impact analysis (for emergency preparedness) of part of Accra, Ghana in a GIS environment.
In the study two categories of DEMs were developed with 5 m contour and planimetric topographic data; bare earth DEM and built environment DEM. These derived DEMs were used as terrain inputs for performing spatial analysis and obtaining derivative products. The generated DEMs were used to delineate drainage patterns and watershed of the study area using ArcGIS desktop and its ArcHydro extension tool from Environmental Systems Research Institute (ESRI).
A vector-based approach was used to derive inundation areas at various flood levels. The DEM of built-up areas was used as inputs for determining properties which will be inundated in a flood event and subsequently generating flood inundation maps. The resulting inundation maps show that about 80% areas which have perennially experienced extensive flooding in the city falls within the predicted flood extent. This approach can therefore provide a simplified means of predicting the extent of inundation during flood events for emergency action especially in less developed economies where sophisticated technologies and expertise are hard to come by.
KeywordsDEM GIS drainage modelling watershed flood modelling ArcGIS ArcHydro
Unable to display preview. Download preview PDF.
- Burrough, P. A. (1986) Principles of Geographical Information Systems for Land Resources Assessment, Clarendon Press, Oxford.Google Scholar
- Chen, C. and Kolditz, O. (2005) DEM-based structural modeling and TIN technology for more accurate terrain in GIS, ZAG Publisher, Tübingen.Google Scholar
- Mark, D. M. (1979) Phenomenon-bases data structuring and digital elevation modeling. Geo-processing 1: 27–33.Google Scholar
- Miller, C. L. and Laflamme, R. A. (1958) The digital terrain model — theory and application. Photogrammetric Engineering 24 (3): 433–442.Google Scholar
- Nyarko, E. K. (2002) Application of a rational model in GIS for flood risk assessment in Accra, Ghana. Journal of Spatial Hydrology 2:1.Google Scholar
- Peuker, T. K. (1978) Data structures for digital elevation models: Discussion and comparison. In Haward Papers on GIS, 5, 1–5.Google Scholar
- Steve Kopp, E. S. R. I., Dean Djokic, E. S. R. I., and Al Rea, U. S. G. S. (2005) Introduction to GIS and hydrology. Proceedings of ESRI International Pre conference Seminars, 2005, www.crwr.utexas.edu/gis/gishydro05/Introduction/Presentation/IntroGISHydro05.ppt.
- Weibel, R. and Heller, H. (1991) Digital terrain modelling, Geographical Information Systems: Principles and applications, Longmann Group, UK.Google Scholar