# URBAN FLOOD MODELING Concepts & Models. 2 Different Approaches For Modeling an Urban Flood Hydrological Approach Objective is to generate a storm hydrograph.

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URBAN FLOOD MODELING Concepts & Models

2 Different Approaches For Modeling an Urban Flood Hydrological Approach Objective is to generate a storm hydrograph at a point on the river for a given precipitation falling on the urban catchment. Land usage maps, impermeability coefficient, infiltration coefficient, street slopes and Manning’s n, gutter locations, sewer network size, lengths and ‘n’, rainfall IDF curves.

3 Rainfall is transformed to discharge which is routed through the network by simplified methods Allows to check the capacity of the network for a given rainfall and possibility of overflow Principal limitation is that no information about the flow velocities and depths is supplied at different points of the urban milieu.

4 Different Approaches For Modeling an Urban Flood Hydraulical Approach Objective is to generate a complete history of flow depths and velocities at different points of the inundated zone at all instants as a function of the input hydrograph. In case of no overflow, the simulation is free surface flow in channels of prismatic x-section. If overflow occurs, determine: peak water depths and velocoties, flood wave advance, limites of the flooded zone, time to peak, inundation duration.

5 Representation of the Urban Area in the Mesh 1.Use of higher value of roughness coeff. for the urban zone. 2.Complete geometric description of the urban area. Downside: too large data, long calculation time, the minimum mesh dimension fixed by the dimension of the habitation. 3.Coarse mesh with cells possessing permeability or porosity coefficients in two directions.

6 Types of Urban Flood Modeling 1.Majority of simulations only represent the overflow from the sewers network. 2.Sewers network saturated only surface flow simulated. 3.Mainly surface flow is simulated with part of the flow passing into the sewers simulated. 4.Fully coupled calculations.

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