Demography Condition Study Area
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problems. This includes large river basin water supply and flood hydrology to small urban or natural watershed runoff. Hydrographs produced by the program
can be used directly or in conjunction with other software for studies of water availability, urban drainage, flow forecasting, future urbanization impact,
reservoir spillway design, flood damage reduction, floodplain regulation, wetlands hydrology, and systems operation Fleming, 2009. HEC-HMS model is a
mathematical model and was designed originally to apply for runoff simulation and hydrological forecasting.
The main concept of HEC-HMS hydrological model is the use of NRCS Curve Number process, the model that can be used to assess the availability of
water on a watershed. The NRCS-CN model’s itself describing how the precipitation entrance to the watershed system through canopy interception, soil
infiltration, percolation, and evapotranspiration. These models also represent the watershed with a series of storage layer such canopy interception storage, surface
depression storage, upper ground storage, and groundwater storage.
Figure 3.11 Conceptual schematic of the continuous soil moisture model HEC-HMS, 2000
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3.4.2 Model Parameter and Input 3.4.2.1 Schematic Watershed Model – Watershed Delineation
First step in hydrological modeling is delineating watershed boundaries and discretize to hydrology response unit. The aim of the watershed delineation
process is to determine the boundary of the watershed and also to break it into smaller management unit sub-basin if necessary. The watershed boundary was
derived from Suttle Radar Terrain Mission SRTM data with 90 by 90 meters of spatial resolution. It divided into seven sub-basins as shows in Figure 3.12. In
additional to determining the catchment boundary and its sub-basins area, the watershed delineation process is also determined the stream network and its
related parameters such as basin slope, river slope, basin distance, river length, etc. The watershed delineation process was done by using HEC-GeoHMS tool
that is can be integrated as plug-in on ArcMap.
Connector Reach
Junction OutletSink
Sub-Basin
Figure 3.12 Schematic network element of HEC-HMS model in Palu catchment