Flood plain modelling with 1D and 2D models
Flood plain modelling with 1D and 2D models
- A Case Study of St. Maarten N.A. -
Dragan Tutulić
Abstract
Urban flooding has become a very important and growing issue around the world. Since it remains to be an inevitable danger, the development of effective flood management plans is of the utmost importance for every country and particularly for developing countries where the financial resources available for flood-related disasters are almost nonexistent. The effects of climate change are suggesting that this problem may become even more devastating in the years to come. Furthermore, the cities are experiencing water logging due to inadequate drainage capacity, poor maintenance of drainage systems and the effect of heavy storm runoff resulting from rapid urbanization. For tropical islands such as St. Maarten N.A., tropical cyclones and orographic rainfall that are usually the cause for severe flash floods are making the life of its residents to be often miserable. In this respect, the development of an efficient and effective flood management strategies based on the results from numerical models can help to considerably minimize the extent of damages and risks. With the need to improve modelling accuracy, the researchers are nowadays investigating new modelling approaches that will enable better description of flood waves across the flood plains. One of the relatively new approaches is a coupled 1D-2D modelling approach where the two-dimensional model of a flood plain is combined with the one-dimensional pipe/open channel flow model. The present MSc study explores the use of such approach on a real-life case study (St. Maarten N.A.) and compares the results obtained from a 1D model. Furthermore, both modelling approaches are compared for the purpose of establishing potential rehabilitation options that could minimize flooding problems on St. Maarten. Modelling software used in this study consists of MIKE 21, 2D free surface flow model, and MIKE 11 model, 1D free surface flow model. The tool used for coupling these two models is MIKE FLOOD.
For the preparation of a Digital Terrain Model (DTM) the ArcView GIS software was used. All modelling results were processed and mapped using a waterRIDE package. The coupled model has been simulated successfully, and the results have been compared with 1D model results as well as with observed flooding for evaluation. The results obtained indicate that both modelling approaches are capable of successfully describing behavior across the flood plain. However, a special caution should be given to the interpretation of 1D model results which appear to be more vulnerable to the variation of topographical features within the flood plain. Therefore, for off-line simulations where the time of computation is not an issue, the coupled 1D-2D modelling approach could be regarded to be more reliable. On the other hand, if it is that one of the two modelling approaches has to be applied to a flood forecasting application, the coupled 1D-2D model will not be suitable as it takes much longer computational time than the 1D model.
Key words: integrated flood plain modelling, 1D-2D approach, GIS framework