Investigating the engineering hydrogeomorphological characteristics of the Gian catchment and river of Nahavand in the Hamadan province

Assessing and understanding the hydromorphological characteristics are necessary to understand the behavior of a river and its active processes. This is useful for understanding the erosion and sedimentation regime and changing the river path, for making correct engineering and human activities in the river's catchment area. The Gian River, with an average annual discharge of 2.3 m3/s, is one of the tributaries of the Gamasiab River in the Hamedan province. From a geological and hydrogeomorphological point of view, the Gian is a small river. It is fully compatible with the geological structures of the region. The calculation of the sinusoidal coefficient has shown that this river is a meandering river whose wavelength, the amplitude of the oscillation and the width of the meander belt are smaller in the mountainous area than in the plain area The gradient of the river bed is relatively low and it is classified as an erosion and sedimentation river in its different sections. The Gian River has a rocky bed in the mountainous part and an alluvial bed in the plain. The Gian River has a small catchment area, and, according to theGravelius' coefficient, its shape is almost elongated. The catchment elevation of the Gian River is between 1455 and 2700 with a weighted average of 1715.20 m.a.s.l. and its area decreases with the increase in the elevation. The concentration time of the catchment is 4.204 hours. The application of the data and results of the research can be very effective in land use planning, engineering and executive applications to predict river changes and protect engineering structures such as roads, bridges, coastal structures and railways, protect agricultural lands in the region and develop tourism.