![]() ![]() Roughness coefficient RIVER BED n (s/m1/3) Dense vegetation 0.080 Some vegetation 0.050 No vegetation 0.033 FLOOD PLAIN Agricultural areas Industrial areas 0.100 Urban areas 0.150 1- delimitate areas of similar roughness 2- assign a value to each area 3- overlay the cross ssections 4- assign each value to each part of the cross section ![]() Sections have been drawn by hand keeping the perpendicularity and a similar space between them (about 100m) Once created the file is imported on HEC-RAS Cross sections ![]() Topography 5m resolution DEM ArcGIS +HEC-GeoRAS Cross sections have been obtained usig ArcGIS with HEC-GeoRAS toolkit. ![]() Mike 11 case Way to solve problem of uniform water level by the implementation of levees Meters Meters Original DEM DEM after bridges extraction Lower Reach of the Var River Basin → Covering the Floodplain Upstream Boundary → La Manda Bridge (observed discharge data) Downstream boundary → Mediterranean Sea Another group to produce outputs for HEC-RAS and another to produce outputs for TELEMAC We would then work together to compare results between our models and to the theoretical findings The var riverġD VS 2D MODELS 1D MODELS 2D MODELS Cross-sections taken perpendicular to river flow (x) Velocity is not considered to be uniform Terrain represented as a continuous surface (x,y) Uniform water level across the cross-section Mathematical governing equations Both 1D and 2D models are based on mathematical governing equations In 1D models many cross-sections are taken which describe the available volume in the system, the slope of channel bed and the roughness 1D models are different in that they are based on the assumption that flow is one-dimensional meaning that velocity is uniform across a cross-section The water level is also assumed to be uniform for a given cross-section With 2D models the terrain is represented as a continuous surface Better for steep gradients Uniform velocity across the cross-section Water depth is not considered to be uniform Better for low gradients Compare the representation of the floodplain for each model In order to meet our aim we identified more main objectives We split the group into 3 parts: 1 to discuss the theoretical processes of 1D and 2D models. Objectives: Discuss processes of 1D and 2D models Produce an output for HEC-RAS (1D). With the 2D model given as TELEMAC Tessie BARJAT Anaïs MAYAU Tamsin JONES Aymeric FRANCOIS Laura TALBA Konlavach MENGSUWAN Andres GONZALEZ INIGUEZ Miquel SARRIAS MONTON Oussama MOKHTARI Chenyu LIU SUPERVISORS TEAM MEMBERS James CELRAY Leslie SALVANĪrea of low-lying ground adjacent to a river subject to flooding Need to understand how water flows in these areas Accuracy of processes: Depends upon the model used Ability to model ‘real processes’ occurring in the floodplain Need to produce a 1D and 2D model – compare 3 November 2011 event chosen In order to begin answering our question we began by defining the terms in our question The floodplain is the area surrounding the river that is subject to flooding during high discharges It is important to model the flow of water here as these areas of often exploited with buildings and agriculture The accuracy of processes we defined as being dependent on the type of model used 1D or 2D We must therefore produce an output of 1D and 2D models and compare their ability to model the floodplain We chose the 2011 event as there was a large amount of data available and it is more recent then 1994, with no issues of gauge failureģ INTRODUCTION Aim: Compare 1D and 2D model processes for the floodplain – find the limitations of processes represented. SESSION 2017 FLOODPLAIN REPRESENTATION AND ACCURACY OF PROCESSES 1D/2D Our question of the week was looking at the floodplain representation and accuracy of processes 1D/2D. Presentation on theme: "FLOODPLAIN REPRESENTATION AND ACCURACY OF PROCESSES 1D/2D"- Presentation transcript:ġ FLOODPLAIN REPRESENTATION AND ACCURACY OF PROCESSES 1D/2D ![]()
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