5. Conclusions

In this chapter, hydrologic response of Boostan dam catchment in 1996 and 2006 simulated using WMS. Land use map investigation showed that the study area has 11 types of land uses. Assessment of changes in land use of Boostan dam catchment in the period 1996–2006 indicates that due to deforestation, more than 1.56% of the area is added to the farm lands. According to the results during the 10-year period, the total forest area has decreased, from 25.67 to 22.50%, and in contrast the rangeland area has increased from 41.53 to 42.63%. So the total forest and rangeland land uses in the catchment decreased almost 3%. Moreover in this period of time, high-density rangeland decreased 78.47 km2 in other words 35.02% of its initial area; semi-density rangeland increased 96.24 km<sup>2</sup> that means 25.89% of its initial area, and low-density rangeland area remained relatively constant. This represents a decrease in rangeland quality of the catchment, which has a negative impact on its flooding. On the other hand, residential area increased more than seven times that has a negative impact on flooding too. It can be concluded that the implemented biological measures during this period of time have been effective to mitigate floods of the catchment.

It can be suggested that forestation in high lands as the main factor to mitigate flooding of a reign should continue and amplify. On the other hand, land management plans should focus on not only changes in main land uses (forest, rangeland) but also degradation in a particular land use, such as decline in quality of rangelands in the current study.
