| Abstrak/Abstract |
Water, a vital natural resource for a human being, could bring negative effects such as flood and
landslides. The best way to show the hydrological process is called “model”. One of them is Modified
Rational Method (MRM). There are several types of MRM base on its equation modification. Hydrological
mass balance or kinematic wave in order to route the flow. With this model modification, the output of the
model is not only peak discharge but also unit hydrograph. Model modification was done in the calculation
of peak discharges by assigning the C value (coefficient runoff), A value (area) and land characteristic (soil
texture, Manning roughness coefficient, and saturation coefficient in the pixel basis. PCRaster software
allows us to perform discharge calculation on each pixel. Flow accumulation by using kinematic wave was
done to get the unit hydrograph. Three (3) flood events were used to run the model validation, i.e. January
21, January 22, and February 10, 2016. Each event has different rainfall characteristics. The result of this
model was DRO hydrograph. Based on the baseflow separation of the observed hydrograph as well as the
hydrograph from the model, we found that the flow through the outlet during discharge recession is the base
flow. The accuracy value is quite good, i.e. 10–30 %. The result of the model shows a different response
between direct runoff and base flow, while time to peak was faster than the recession time. |
