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.
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• 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.
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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.
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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.
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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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