A Variable Distributed Clark Unit Hydrograph Model for Urban Drainage
System with Different Rainfall Intensity
Abstract
Based on Clark unit hydrograph model, a variable distributed unit
hydrograph model for urban drainage system is presented with different
rainfall intensity. Firstly, urban watershed is decomposed into several
individual sub-catchment units; then, different unit hydrograph for each
sub-catchment unit is modeled as a single linear reservoir; finally
different unit hydrograph is delayed and summed to outlet according the
time of concentration along underground pipe network. The values of two
model parameters including response parameter and delayed time of
concentration can be directly estimated without the need of calibration
considering the effect of rainfall intensity on flow velocity. The north
region of Future Science Park in Beijing was selected as the study area,
application results showed that: (1) the unit hydrograph for whole
catchment area was different, in which the peak values increased with
the increase of rainfall intensity, and the increasing rate showed
gradual decrease tendency; (2) the simulated runoff processes are in
reasonable agreement with the monitored runoff processes, in which the
average value of R2 was 0.73, which varied from 0.4 to 0.89, the average
value of NSE was 0.26, which varied from -0.77 to 0.87, the average
value of RE was -0.18, which varied from -0.77 to 0.36; (3) the unit
hydrograph for each sub-catchment unit was spatially varying, and varied
with the rainfall intensity, in which with the increase of rainfall
intensity, the response parameter increased by the 0.4 power function
and delayed time of concentration decreased by the -0.6 power function,
respectively.