Urban flood modeling
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URBAN FLOOD MODELING. Concepts & Models. 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.

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URBAN FLOOD MODELING

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URBAN FLOOD MODELING

Concepts & Models


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.


  • 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.


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.


Representation of the Urban Area in the Mesh

  • Use of higher value of roughness coeff. for the urban zone.

  • 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.

  • Coarse mesh with cells possessing permeability or porosity coefficients in two directions.


Types of Urban Flood Modeling

  • Majority of simulations only represent the overflow from the sewers network.

  • Sewers network saturated only surface flow simulated.

  • Mainly surface flow is simulated with part of the flow passing into the sewers simulated.

  • Fully coupled calculations.


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