Courtesy of National River Flow Archive
Updating the ReFH design hydrograph method
for UK catchments
Lisa Stewart, Maliko Tanguy – CEH
Thomas Kjeldsen - University of Bath
Chris Nicholls, Tracey Haxton, Andy Young – Wallingford HydroSolutions
Outline of presentation
• Background to ReFH design method
• Motivation for revisiting the design method
• Updates to the design method*
• Software development plans (ReFH 2)
* Kjeldsen, T. R., Miller, J. D., Packman, J. C. (in press)
Modelling design flood hydrographs in catchments with
mixed urban and rural land cover. Hydrology Research.
The Revitalised Flood Hydrograph (ReFH) model
Total rainfall
(P, D, profile)
Net rainfall
Initial soil moisture
Cini
Initial baseflow
BF0
Loss
model
(Cmax)
Routing
model
(Tp)
+
Total flow
Baseflow model
(BR, BL)
In design mode requires:
• Four parameters (Cmax, Tp, BR, BL)
• Design inputs (Design storm, Cini, BF0,  )
Motivation for revisiting the design method
• To update parameter estimation equations using
URBEXT2000
• To improve model performance in permeable
catchments
• To address inconsistencies with improved FEH
statistical method (WINFAP-FEH 3)
•
•
To address climate dependencies of 
Extension of model calibration to 1 in 1000-year return
period
• To update the modelling of urbanised catchments
in line with recently published research
1: Updated parameter estimation equations
• Model form has been reassessed
• Alternative formulations developed to avoid geometry-based
catchment descriptors*
Formula
r2
fse
Tp
Tp = a PROPWETb DPLBARc (1+URBEXT2000)d DPSBARe
0.80
1.30
Tp*
Tp = aPROPWETb AREAc (1+URBEXT2000)d SAARe
0.71
1.36
Cmax
Cmax = aPROPWETb exp(c * BFIHOST)
0.60
1.29
BL
a PROPWETb DPLBARc (1+URBEXT2000)d BFIHOST e
0.35
1.49
BL*
a PROPWETb AREAc (1+URBEXT2000)d BFIHOST e
0.31
1.51
BR
BR = aPROPWETb BFIHOST c
0.36
1.48
Parameter
1: Updated parameter estimation equations
2: Modification of Cini (initial soil moisture)
• Where BFIHOST is high and PROPWET is low (dry,
permeable catchments) it is possible to get negative values
of Cini in ReFH 1
• Resolved using exponential model with separate equations
above and below BFIHOST = 0.65
3: Modification of  & extension to higher return periods
Adjustment coefficient, , is introduced to the loss model to
allow rainfall and flood return periods to correspond:
•
•
Calibrated to 1000-year event
Incorporates relationship with SAAR
3: Modification of  & extension to higher return periods
Adjustment coefficient, , is introduced to the loss model to
allow rainfall and flood return periods to correspond:
•
•
Calibrated to 1000-year event
Incorporates relationship with SAAR
3: Modification of  & extension to higher return periods
Adjustment coefficient, , is introduced to the loss model to
allow rainfall and flood return periods to correspond:
•
•
Calibrated to 1000-year event
Incorporates relationship with SAAR
4: Treatment of urbanisation
• Based on newly published work by Kjeldsen,
Miller and Packman (in press):
Explicit consideration of urban land cover improves
the predictive ability of the ReFH model
Configurable parameters
•
•
•
•
•
•
Summer Cini (based on multiplier of winter Cini)
Urban Tp (multiplier of rural Tp)
Percentage of urban area that is impervious
Percentage runoff from impervious areas, PRu
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