Pages: 12-22

Abstract

Lisar watershed is one of the main areas at the east of Gilan which is a component of Gorganrood of Talesh province in terms of political divisions of this area. This study has done by the aim of study the morphologic changes of the river due to river material removals in Lisar River. For this purpose, by studying and identifying physical and hydrological features of the basin, the rate of annual sediment load was calculated which is including load floor, suspended load using sediment rating curves. And the rate of authorized removal of river materials was obtained according to calculations of total sediment 42/22 thousand tones in a year in the average flow rate and when syllabic is 140/25 thousand tones in a year. The amount of authorized removal of materials during a year is 2.85 thousand tones in a year or is equal to 7.8 tones in a day. However, the rate of material removal from Lisar River is calculated more than authorized amount. Fall of the river and consequently increasing slope and in results increasing speed and power of flow is cause to being active floor action and wall corrosion especially in the end point of the road.