Enhancement of digital elevation models and overland flow path delineation methods for advanced urban flood modelling
Leitao, Joao Paulo Correia
PublisherImperial College London
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The objective of this thesis is to improve existing and develop new DEM enhancement methods and DEM-based overland flow delineation methods in order to generate reliable overland flow networks. These networks can be used in conjunction with existing urban drainage modelling methodologies in order to improve surface flooding simulation results. The objective has been achieved by: developing new methods to merge DEMs; evaluating nad improving available DEM enhancement methods; improving methods to solve DEM flat area problems, and developing novel methods to improve overland flow path delineation. All improvements and new developments have been adapted to the specific characteristics of high-resolution DEMs and urban catchments. The experimental work undertaken in Lisbon, together with two case-studies in the UK, was used to validate the concepts proposed in this thesis. It is concluded that DEM enhancement methods can be used to improve DEMs for overland flow delineation, thereby enhancing the reliability of urban flood modelling. The advanced flow path delineation methods developed here produce more reliable results than conventional overland flow path delineation methods. The hydraulic simulation results obtained confirm the advantages of applying 1D/1D modelling to simulate urban flood events. However, the findings show that the use of these methods needs to be preceded by a thorough analysis and quantification of Dem surface characteristics, and by a detailed calibration and validation procedure. Independent testing carried out by UKWIR has proved the adequacy and reliability of the developed methodology in full scale flood risk mapping applications.