جستجوی مقالات مرتبط با کلیدواژه « مدل بارش » در نشریات گروه « عمران »

Rainfall Runoff modeling especially in ungauged watersheds is almost dependent on hydro-geomorphologic data. In this regard, the effects of data and DEM resolution on deriving watershed’s geomorphologic data such as subbasins area, channels and subbasins’ slope should be well realized in modeling. In this research, HEC-HMS as the rainfall runoff model and two subbasins with different areas, geomorphologic properties and climate were selected for studying. By reducing the cell size of the DEM derived from a topo map, simulated peaks increased. For DEM cell sizes less than 100 m, the differences in simulated peak were limited to 2 to 5%. Using SRTM DEMs against the topo DEM at the scale of 1:25000, representing the effects of data resolution in rainfall runoff modeling, led to obtaining higher flood peaks at the two watersheds. Such an outcome was obtained for time to peak, hydrograph base time, and the slope of hydrograph rising limb. Change of SRTM DEM resolution affected the model output more than the case of using topo DEM. Decreasing DEMs resolution by decreasing information content of the topo DEM reduced differences in the model output when using two different sources of DEM. Furthermore, it is concluded that the extent of scale effect in modeling could not be inferred by watershed size. It was illustrated that HEC-HMS application in a watershed of more diversity was more sensitive to data resolution. Using cell size of 100 m and less could guaranty the result of the HEC-HMS application regardless of DEM origin and size of watersheds. Rainfall Runoff modeling especially in ungauged watersheds is almost dependent on hydro-geomorphologic data. In this regard, the effects of data and DEM resolution on deriving watershed’s geomorphologic data such as subbasins area, channels and subbasins’ slope should be well realized in modeling. In this research, HEC-HMS as the rainfall runoff model and two subbasins with different areas, geomorphologic properties and climate were selected for studying. By reducing the cell size of the DEM derived from a topo map, simulated peaks increased. For DEM cell sizes less than 100 m, the differences in simulated peak were limited to 2 to 5%. Using SRTM DEMs against the topo DEM at the scale of 1:25000, representing the effects of data resolution in rainfall runoff modeling, led to obtaining higher flood peaks at the two watersheds. Such an outcome was obtained for time to peak, hydrograph base time, and the slope of hydrograph rising limb. Change of SRTM DEM resolution affected the model output more than the case of using topo DEM. Decreasing DEMs resolution by decreasing information content of the topo DEM reduced differences in the model output when using two different sources of DEM. Furthermore, it is concluded that the extent of scale effect in modeling could not be inferred by watershed size. It was illustrated that HEC-HMS application in a watershed of more diversity was more sensitive to data resolution. Using cell size of 100 m and less could guaranty the result of the HEC-HMS application regardless of DEM origin and size of watersheds.

Short time interval rainfall data (e.g. hourly data) serve as inputs to a range of flood and pollution transport models. However, they are not usually available. Due to availability of daily data as measured values, in this study an attempt is made to examine the suitability of a random cascade model for transformation of observed daily rainfall data measured at the rain gauge station situated on the Amameh catchment, north of Tehran, Iran. A random cascade model was proposed for the first time by Olsson (1998). The cascade model presented here is based on exact conservation of rainfall volume together with the rainfall seasonality. Having applied this model to the data measured with the mentioned rain gauge, 45-minute data were simulated and compared with its corresponding measured data for the same period of daily data. It was observed that the modelling procedure employed and used in this study can simulate the 45-minute peak values much better that the previous models such as the Olsson one. The potential for the better estimation of peak discharges is, therefore, has the potentiality to be used in storm design purpose as far as the application of rainfall-runoff models for flood estimation are concerned.