Enhancing Flood Hazard Estimation Methods on Alluvial Fans Using an Integrated Hydraulic and Geological and Geomorphological Approach

Abstract

Abstract. Due to the uncertainty concerning the location of flow paths on active alluvial fans, alluvial fan floods could be more dangerous than riverine floods. FEMA used a simple stochastic model named FAN in this regard for many years. In the last decade, this model has been criticized as a consequence of developing complex computer models. 15Instead, more recent hydraulic models with capability of avulsion simulation were recommended. This study was conducted on three alluvial fans located in the northeast and southeast part of Iran using combination of FAN model, FLO-2D model and geomorphological information. Initial stages included three steps: a) identifying the alluvial fans' landforms, b) determining the active and inactive areas of alluvial fans, and c) delineating 100-year flood within these selected areas. This information was used as an input in the mentioned three approaches of: I) FLO-2D model, II) 20 geomorphological method, and III) FAN model. Thereafter, the results of each model were obtained and Geographical Information System (GIS) layers were created and overlaid. Afterwards, using a scoring system, the results were summarized and then the integrated method was compared with the three approaches.