Spatial correlation analysis of vegetation changes with runoff height in Gorganrood Watershed

In recent years, flood phenomenon has been one of the hydroclimatic events and one of the most serious natural hazards that has threatened human societies. Indiscriminate exploitation of forests and pastures and land use change and their transformation into unsuitable agricultural lands, along with the indiscriminate construction of residential areas, have caused an increase in floods. Therefore, the flood phenomenon is very important. Therefore, the present study was conducted with the aim of analyzing the spatial correlation of changes in vegetation cover with the height of runoff in the Gorgan River watershed in a 21-year period. For this purpose, from the data of slope, soil type, land unit and land use to prepare the hydrological response unit and Landsat images of different years (2000-2021) to investigate changes in vegetation density using the NDVI index in each of Hydrological response units are used. In this regard, 72 hydrological response units were prepared as basic units in the study area. Also, the height of the runoff was calculated by the SCS method in each of the hydrological response units using the criteria of rainfall height, soil hydrological group, vegetation, land use type and soil texture, so that the cities of Agh Qola, Simin Shahr and Gomish Tepe and the Gorganrood River in the height of the runoff There are many. The results of the analysis of 78% of the spatial correlation between the height of runoff and the density of vegetation showed that the agricultural and garden lands in the plains have increased significantly, while the density of forest and pastures has decreased in the 21-year period. This factor is caused by human activities such as the destruction of forests and pastures and the cultivation of these lands and the development of cities, the height of the runoff has increased. While in the highlands, due to more infiltration, despite the decrease in vegetation density, the runoff height is also low.