Introduction
Physiography and topography of basins, including height and slope, can be used for many weather factors such as temperature and its changes, the type of investigation and recognition of physiographic and hydrogeomorphic characteristics of basins in the field of various issues such as watershed estimation, basins, flood forecasting, watershed management In order to reduce the damage caused by the flood event, it is important to manage water resources, plan for dam utilization, build bridges and crossing structures and other water resources and watershed management projects. Among natural hazards, floods are more threatening than other hazards in the world (Henononin et al., 2010). In addition to human factors, geology and the type of formations, soil, vegetation, amount and type of precipitation, the shape of the basin, the slope of the basin, the state of drainage networks and river characteristics, are among the most important factors and physiographic and morphometric parameters that play a role in the flooding of basins. The watershed as a framework and geomorphological unit includes river morphosystems, which Shum (1985) defines as a wide area including divided drains in the place of water and sediment accumulation, channel path and valleys of the drainage basin and the sediment deposition area of the same oceans.

Materials and methods
This area is a part of the watershed of the Kabir River and geologically it is located in the heights of North Alborz and Central Alborz. The foothills not only comprise the majority of the natural landscape, but also provide a complete part of the drainage system, providing water and sediment for the river. Curvature is defined as a three-dimensional property of a two-dimensional surface and indicates the degree of surface deviation from flatness, or in other words, the convexity and concavity of the domain. As the curvature increases, the tensile force increases along the surface and causes fractures. By using numerical values and derivatives obtained from DEM such as slope, profile curvature, plan curvature, transverse curvature and general curvature of the domain, physiographic features and hydrogeomorphology are extracted.

Results and discussion
Analysis of hydrogeomorphological and physiographic factors of the studied area: Geological formations: The geological layer of the area is created from the 1:250,000 geological layer by creating a polygon (UTM system) and completing the information table in Arc Map. After classifying the geological layer, the area and the percentage of the area of each of the layers obtained, which can be seen according to table (1), most of the area is shale and sandstone with an area of 78206036.76 square meters (86.94%), massif limestone with orbitulin. (Tizkoh Formation) with an area of 4205469.20 square meters (0.17 percent). Most of the study area of the basin is located in Mesozoic and Cambrian-Jurassic geological periods. The north and south-west parts are made up of different rocks, the most important of which, after the mentioned ones, is limestone.

Conclusion
Among the most important physical characteristics of a watershed, we can mention the area, height, slope, direction of slope, land use, vegetation, slope curvature indices, surface curvature, and cross-sectional curvature. On the other hand, it is very important to investigate and understand hydrogeomorphological factors and characteristics and how they affect watershed management in order to reduce damage caused by hazards. Therefore, the aim of this research is to evaluate the hydrogeomorphological and physiographic features of the Kabir River watershed using RS and GIS techniques. In this regard, topographic, geological and Landsat 8 satellite images from 1403 were used to extract and produce operational maps. Therefore, the slope map of the area was produced using DEM (30 meters) slope map. Most of the limited area of the studied case is located between 25 and 75 percent. More than 42,000,000 square meters, which is equivalent to 50% of the total area of the study area in the 25 to 40 slope class, which is the same and evident in most parts of the region. The slope above 120% in the northern and southern halves is due to the processes of the trough of the river and the unevenness of this part. In the present study, the slope direction was determined using Arc GIS software and divided into eight groups of main and sub-geographical directions.
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