Combining Remote Sensing and Techniques for Rainfall Runoff Modelling and Flash Flood Mapping in the UAE

  • Benhur Asefaw

Student thesis: Master's Thesis

Abstract

This research work focused on preparation of a continuous hydrological based model to monitor the variability of surface runoff and subsequently to prepare flash flood maps using remote sensing and modelling mechanism. The study case is the wadi Ham in the North eastern part of the United Arab Emirates (UAE). Phase one of the project involved the rainfall-runoff modelling of Wadi Ham in a continuous, distributed modelling approach. Hydrologic Engineering Centre Hydrological Modelling System (HEC-HMS) was adapted as the simulating model. The bulk precipitation data obtained from Global Precipitation Measurement (GPM) mission (1 day, 0.10 product) was automatically imported to HEC-HMS after specifying various parameters such as soil property, temperature and routing method for the runoff. After running the model, simulated runoff hydrographs and volume at the outlet section (Ham/Fujairah Dam) were generated. Area of Imperviousness was found to be sensitive. After calibrating the model using this variable, a significant similarity result (only 8% difference) was observed between the estimated and observed volume for the March 13, 2016 event. Landsat-8 images were used to extract the observed area of the water body. With 2% of the basin area impervious, the model gave a relatively smaller difference (RMSE of 0.24) for all events considered between the simulated and the observed volume of water at the reservoir. The second phase comprises the hydraulic simulation and generation of flash flood maps within the wadi basin. The simulated and validated maximum runoff hydrographs obtained in the hydrologic model (first phase) were used to perform 2D hydraulic modelling in Hydrologic Engineering Centre River Analysis System (HEC-RAS). Moderate Resolution Imaging Spectroradiometer (MODIS) land cover of the area (daily, 0.5km product) was used in specifying the manning roughness coefficient based up on the type of the land cover. Flood hazard maps and maximum water depth profiles at various sections were finally prepared after the defining the boundary conditions. These hydrologic and hydraulic simulated results gave an insight and are expected to contribute to an improved managerial system in water resources and also in identifying flash flood vulnerable areas during similar magnitude rainfall events in that area of the UAE. As a recommendation, and for the adapted hydraulic model to be used efficiently, a very fine resolution, 10 m or less, digital elevation model (DEM) with cloud free satellite images of the wadi during floods are necessary. These simulation models performed can play an important role in the direct assessment of the impact of future developments on the surface and subsurface water dynamics, and increasing in the national water storage capacity as per the UAE water security strategy 2036.
Date of AwardNov 2020
Original languageAmerican English
SupervisorAnnalisa Molini (Supervisor)

Keywords

  • Flood map
  • GPM
  • Hydrologic modelling
  • HEC-HMS
  • HEC-RAS
  • Landsat
  • Wadi Ham.

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