Effect of Curve Number on Flood Hydrograph in a Quick Reaction Basin ( case study: Khiyavchay Basin, Ardabil)

Kazemi, Seyyedeh Zhila (2017) Effect of Curve Number on Flood Hydrograph in a Quick Reaction Basin ( case study: Khiyavchay Basin, Ardabil). Masters thesis, University of Mohaghegh Ardabili.

Preview

Text (اثر شماره منحنی روی هیدروگراف سیلاب در یک حوضه عکس‌العمل سریع (مطالعه موردی: حوضه خیاو‌چای اردبیل)) Zhaleh Moharrami Oranj.pdf Download (1MB) | Preview

Abstract

Runoff and the relationship between rainfall and runoff are one of the most important and fundamental issues in hydrology .To control flood, primarily areas with high potential for flood production, then the factors affecting the production of runoff should be identified. Watershed Modeling System (WMS) is one of softwares that can simulate flood hydrograph, according to the required parameters. Land use changes is one of the important factors in hydrologic flow changes, watershed erosion and reducing biodiversity. Land use change affects the curve number and consequently discharge and flood hydrographs. The study area is Khayawchai watershed, with an area of about 134 square kilometers in the west of Ardabil province, south of Meshkinshahr city and northwest of Sabalan volcanic masses. The aim of this study was to evaluate the effect of curve number changes on flood hydrograph in a quic reaction basin. In this study, the maximum daily precipitation of 11Rain gauge stations was used and reconstructing the missing data values by Normal Ratio Method. Homogeneity and normalization of the data were controlled by SPSS software and the Easy Fit Software was used to select the best distribution funetion. Using the Pearson type 3 distribution (as the best probabilistic distribution function), was calculated daily rainfall for the return period of 2 to 100 years. The maximum daily rainfall were used by GIS software and the normalization of the data was re-controlled, also interpolation by the IDW method. The mean daily maximum rainfall was converted to 6-hour, for different return periods. Rainfall patterns of SCS and WMO were compared and WMO rainfall pattern was selected. Maximum flood flow was calculated with Easy Fit for the return periods of 2, 5, 25, 50 and 100 years. Physiographic maps of basin including slope, aspect, curve number and the hydrologic group map were prepared using GIS. With Arc Hydro, the DEM map was modified. Flood hydrograph was simulated for return periods of 2 to 100 years and simulated maximum flood flow compared with observea maximum flood flow. Relative error (RE) and root mean square error for 2 to 100 years return period were obtained 19.13 % and 8.68 m3/s, respectively. The results of simulation of flood hydrograph showed that, with increasing return period, maximum flow increases with a higher slope. The effect of CN chaging in low return periods is more than that of in high return periods so that, 25% increase in CN caused increase in flow by 63 times for 2 return period, while 6.38times for 100 return period. The results indicate that the least change in the land use (to reduce permeability) causes an intense increase in flood discharge in the region.

Actions (login required)

View Item