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| Titel |
GIS Methodology for determination of the flash flood hydrograph in small scale mountainous catchments |
| VerfasserIn |
Matei Domniţa, Augustin Ionuţ Crăciun, Ionel Haidu, Okke Batelaan |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250052557
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| Zusammenfassung |
| The application of a model for estimation of the flash flood hydrographs in small
mountainous catchments is presented. The model is an implementation of a workflow
that combines several well known hydrologic methods in a GIS environment to
obtain an estimated flash flood hydrograph in a point when the terrain and storm
characteristics are known. The model is automated, and only requires the input of
some parameters related to the precipitation and spatially distributed terrain data
like land use, soil and antecedent soil moisture. The result is the estimated flash
flood hydrograph at the catchment outlet. Other intermediate results include the
spatially distributed runoff depth, runoff coefficient and travel time to the catchment
outlet.
The main reason for using this model instead of other already available models is the
dimension of the catchments where the model will be applied. Most models are developed
for larger catchments where streams contribute highly to the discharge. In small
mountainous catchments surface runoff, rather than streamflow plays a major role
in discharge generation. The model consists of four components that calculate:
the spatially distributed runoff depth and runoff coefficient; linear runoff routing
according to the flow velocity; the discharge and the interpolation of the discharge
values to obtain a hydrograph. The first three spatially distributed components of
the model were built using ArcGIS Model Builder and the last calculation and
interpolation of discharge values was built as a script in MATLAB. The runoff depth is
calculated using the hydrologic soil group, land use, and soil hydrologic condition
rasters by the SCS-CN method. The runoff coefficient is calculated as the ratio of
runoff depth to the total precipitation. The travel time to the catchment outlet is
obtained using a flow velocity raster and a DEM and by summing the travel time for
each cell downstream until the outlet. Linear runoff routing according to this travel
time and flow direction was chosen because these small catchments usually have
short stream lengths and hydraulic methods would make the model too difficult to
apply with available data. The discharge generated in each raster cell is calculated
using the rational method and summed according to the travel time at the catchment
outlet. The result is a table of discharge values estimated at a fixed interval until the
concentration time is reached. A hydrograph is then generated in MATLAB by
interpolating the discharge values and plotting the result. This hydrograph can be
interpreted and used as a warning tool for flash flood for a predicted rainfall as an
input.
The model is applied to the CÄăpuş catchment, which is part of the lower Apuseni
mountains in the Northwest of Romania. Its altitude ranges from 459 to 1017 m. Three
subcatchments comprising 17.2, 57.8 and 103 km2 were selected in this area. The validation
of the results was not possible for all catchments because of the lack of gauges in the
area. The value of the maximum discharge in the largest subcatchment is in the
range of measured discharges in similarly sized and nearby gauged catchments. |
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