Investigate the Effect of Extending Dry land Area on Annual Peak Flow Variation Trend (Case study: Ghizilozan Basin)
2006
Rezaei, Ali
The vegetation cover destroying and extending dry land area on all over the countryâs basins are the causes of increasing runoff coefficient and flood intensity. For monitoring trend of temporal variation of annual maximum peaks flow in Ghizilozan basin, the annual Max. Peak flows and Max. 24h. Rainfall data have been gathered from all stations of climatology and hydrometry that located inside the case study basin. The acquisition data repaired and standardized to period of 30 years. Then the data divided into 3 categories with period of 10 years and again combined together and finally 6 categories with period of 10 to 30 years were produced. The mean of variables for every period was calculated based on 2 years return period by fitting the distribution function of Pearson type III to selected data series. The mean of every category plotted with time period and fitted a line to them. The results show that based on Kendallâs tau method, there are significant and positive harmonizing between measures variations to along time only in two climatology stations named Gitoo and Salamatabad and so two hydrometry stations named Sarcham and Dehgolan and in the others there arenât any positive or negative harmonizing of data variations to along time. But the slope of regression line of max. 24h. of annual rainfall as an index of climate variations to the time, equal 0.031 and in contrast the slope of regression line of peak flow to time equal 0.059. Therefore the slope of peak flow is 1.9 times of max. 24h. of annual rainfall with time. This finding says that the vegetation cover because of dry land extending is destroyed and runoff coefficient and flood intensity is increased at studied basin.
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