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Analysis of the relative contributions -( hydrographs ) of the sub-catchments during the flood. Contents. Interpolated Rainfall :« simple to complexe » methods Hydrographs calculation SCS Method Calibration of MIKE SHE for the VAR catchments Parameters , values , graphs
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Hypothesis : Spatial distribution of the rainfall are the same on the all catchment
=> mean of the six rain gauges station
Interpolation by kriging for eachsub-catchment and for eachhour
SCS Method (Soil Conservation Service)
Hypothesis 1: Infiltration capacity tends to zero as time increases.
Hypothesis 2: Runoff appear after it dropped some rainfall.
Hypothesis 3: R (t) = [ si Pu (t) > 0 ]
Firstcalibration-usingonly MIKE SHE
Using: 300 m gridsize
Experiences : verylittlepeak of runoff
thewidth of theimaginedriverbed is 1500 m
riverbed, bighydraulicradius and littlewaterdepth
littlevelocity and discharge
wehavetouserivernetworkfor modelling couplingwith MIKE11
Parameters of the best calibration: M=24 m1/3/s
IWD = 0.000 m
DS= 0.00 mm
Results of calibration: PeakofdischargeQc= 3701 m3/s Qm= 3680m3/s
Wrongtime of thepeak 2.5 hoursdifferences
sensitivityanalysisnotsensitive M,IWD,NRF littlesensitive DS
Conclusions: Wecan’tcalibrate more accuratelyundertheseconditions (300 gridsize) and It’snotnecesserybecausetherearenotobserveddata!
The runoff’speak and timingdependsonthefollowingparameters:
Shape of thecatchment
same Landuse more than 90% forest and natural areaexcept Down Var sub-catchmentsimilar topography
Differences: rainfall, area, shape of thesub-catchments
Relativecontributions of runoff: Q%=∑Q/QiA%=∑A/Ai
Esteron:20% c= Q%/A%=128%
Tineé: 32% c=120%
Upper Var: 36% c=93%
Down Var: 4% c=74%
Relativecontributions of runoff: Esteron:21%
Upper Var: 36,5%
Down Var: 1,5%
The relative contribution of sub-catchments only depends on the distribution of rainfall.
The Tinee, Upper Var, Esterongave more than 90% of thewholerunoff.
CONCLUSIONS OF MIKE PART:
Ifwecalculatetherelativecontributions of thesub-catchments (duringtheflood), wedon’tneedtousecalibrated modell, becausetherelativecontribution is notsensitiveforthecalibratedparameters.