1/5/2024 0 Comments Stone flood wallPluvial flooding is a result of overland flow and ponding before the runoff enters any watercourse, drainage system or sewer, or cannot enter it because the network is full to capacity, usually caused by intense rainfall. These precise measurements contribute to rectifying the TanDEM-X elevation data and thus improve the surface runoff network for the future floodwater model and should enhance the floodwater prediction for the Cuvelai Basin. The surveyed road dam elevation data have a vertical accuracy of 4.3 cm up to 10 cm. This method is not dependent on classic reference stations next to the GNSS sensor but instead works with geostationary satellites sending correction data in real time. For that reasons, the Leica SmartLink function was used. Moreover, the lack of reference stations made a RTK and Network-RTK solution likewise impossible. Due to the long driving distances, the daily regular adjustment of the base station would have been necessary but logistically not possible. In total, 532 km of road dams have been investigated during 4 days while driving at a top speed of 80 km/h. First, a Leica GS 16 Sensor was installed on the roof of a car recording position data in real time while driving on the road dams in the Cuvelai Basin. To fulfil the objective, the main road dams were surveyed, especially those that are blocking the flood water flowing from south Angola to the Etosha Pan in northern Namibia. road dams and culverts, have to be included for precise calculations. Especially in the context of 2D-hydrodynamic flood modelling, the features that influence the runoff processes, e.g. Nevertheless, regarding special usage they sometimes reach their limits in documenting important features that are smaller than the grid size. Modern satellite systems like TanDEM-X deliver high-resolution images with a high vertical and horizontal accuracy. The aim of this study is the improvement of the TanDEM-X elevation model for future floodwater modeling by implementing surveyed road dams and the use of filter algorithms. The comparison of the results and modelling processes of both approaches give insights into the advantages, disadvantages and difficulties or limitations of each presented approach. Special focus is given for the integrated approach to the difficulties occurring during the model optimisation and calibration. For the second approach, the DRM is applied over the whole catchment by the use of HEC‐RAS. In the first approach, the hydrological model (HEC‐HMS) from the Hydrologic Engineering Center (HEC) is used to generate the inflow boundary hydrographs for the 2D model (HEC‐RAS), which is then used to simulate the flow variables for the river network and its floodplains. The resulting flood maps and flow hydrographs are compared for selected rainfall–runoff events in a catchment located in Central Germany. In this study, both modelling approaches are applied and evaluated for their suitability to determine flood hazards in small, rural catchments. This ‘integrated approach’ aims to include hydrological and hydraulic processes in one single model. However, for urban floods, the distributed rainfall is set directly as input (‘direct rainfall modelling’ – DRM) to the elements of the 2D model. The catchment hydrology is determined by empirical semi‐distributed rainfall–runoff models, the flood processes by the use of hydrodynamic models. The classical ‘decoupled’ approach for fluvial flooding makes use of hydrographs as input boundary conditions. This paper would help urban flood managers, and potential users undertake effective flood modeling tasks, balancing between their needs, model complexity and requirements of both input data and time. Each of these techniques is described, by taking aspects influencing the selection of a proper flood modeling method for a particular application into account. The existing methods are categorized into: rapid flood spreading, one-dimensional sewer, overland flow (1D and 2D), sewer-surface coupling approaches (1D–1D and 1D–2D). This paper gives an overview of prevailing flood modeling approaches in view of their potentials and limitations for modeling pluvial flood in urban settings. With respect to effective flood modeling, particularly in urbanized floodplains, the choice of an appropriate method, considering contextual requirements, is challenging. Likewise, several hydrodynamic models have been developed and their application has been spread. Regarding flood risk management, flood modeling enables to understand, assess and forecast flood conditions and their impact. Pluvial flood has been increasingly understood as a major threat that has presented a significant risk for many cities worldwide.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |