Journal of Geography and Geology; Vol. 5, No. 3; 2013 ISSN 1916-9779 E-ISSN 1916-9787 Published by Canadian Center of Science and Education 101 Post Seismic Debris Flow Modelling Using Flo-2D; Case Study of Yingxiu, Sichuan Pronvince, China Mamodu Adegbe 1 , Dinand Alkema 2 , Victor G. Jetten 2 , Ako Thomas Agbor 1 , Idris Nda Abdullahi 1 , Onoduku Usman Shehu 1 & Abraham Stephen Unubi 1 1 Department of Geology, Federal University of Technology, Minna, Niger state, Nigeria 2 Department of earth system science analysis, ITC, University of Twente, Enschede, Netherlands Correspondence: Mamodu Adegbe, Department of Geology, Federal University of Technology, Minna, Nigeria. Tel: 234-703-049-6207. E-mail: adegbemamodu@futminna.edu.ng Received: June 19, 2013 Accepted: July 31, 2013 Online Published: August 7, 2013 doi:10.5539/jgg.v5n3p101 URL: http://dx.doi.org/10.5539/jgg.v5n3p101 Abstract In many parts of the world debris flows are one of the most dangerous of all mass wasting events. Mountainous areas with high slope instability, high seismic activities and extreme rainfall condition are the main triggering factors. The Monday, May 12, 2008, mega-earthquake of magnitude 8.0 that struck the Wenchuan area, Northwestern Sichuan province in China was catastrophic. This event, led to co-seismic landslides and subsequent rainfall induced debris flow in Yingxiu catchment on August 14 th , 2010. The catchment has a very steep topography, an area of 5.35 km 2 and a channel length of 3.55 km. The aim of this research is to model the post seismic debris flow, Parameterize and calibrate the event. Two main initiation zones were identified based on susceptibility assessed from geomorhological mapping and formed the bases for input in the FLO-2D model. 161, 350 m 3 (64.54%) of the debris flow volume was modeled with FLO-2D in a manner consistent within the limit of the data available. FLO-2D model do not incorporate entrainment of materials in the transport zone. Thus, limitation to the production of the total deposits volume on the debris flow fan. The model was parameterized and the result shows that, Sediment concentration and the coefficient of friction were the two main parameters that affected the velocity of debris flow, area of inundation and the impact force respectively. Finally, the debris flow was calibrated using a back analysis of the debris flow event of 2010. Keywords: Seismic, debris flow, FLO-2D model, parameterize, calibration 1. Introduction In many parts of the world debris flows are one of the most dangerous of all mass wasting events. Mountainous areas with high slope instability, high seismic activities and extreme rainfall condition are the main triggering factors (Huang & Li, 2008). Debris flows are also referred to as mudslides, mudflows, debris avalanches, or hyperconcentrated flow (Kowalski, 2008). Debris flow is a common type of landslides that occur generally during intense rainfall on water saturated soil. They can occur suddenly and inundate entire towns in a matter of minutes. Also, the mass can travel long distances over fairly gentle slopes damaging structures and many other elements that lie in their paths (Kowalski, 2008). Different elements at risk such as people, building and infrastructures, whether in urban or rural environments, are either directly or indirectly affected by the occurrence of these events, disturbing their economy, development and sustainability. The Monday, May 12, 2008, mega-earthquake of magnitude 8.0 that struck the Wenchuan area, Northwestern Sichuan province in China was catastrophic Tang et al. (2011). This high intensive earthquake disturbs the slope bedrock and creates an abundance of loose landslide debris on the slopes and gullies and maybe reactivated old landslides. This affects the stability of these slopes for a long period of time. The debris later serves as source material for rainfall induced debris flows as reported by Lin et al. (2006). The Yingxiu town was devastated by large debris flow in August 14, 2010 after rainfall events of short duration. The debris flows from the catchment produced a debris dam which then changed the course of the Minjiang River and resulted in the flooding of the Yinxiu town, including the newly reconstructed settlement. This catastrophic flood event claimed the lives of 56 people. More than 5,500 residents at high risk were forced to evacuate (Tang et al., 2011).