Factors affecting collapse in gates and its economic consequences in the flood water spreading systems (case study: kowsar aquifer management station)

Flood water spreading (FWS) is one of the water resources management strategies in arid and semi-arid regions aiming at water harvesting, artificial aquifer recharge and optimum utilizing of floodwater. There are three kinds of drops (gates); vertical and inclined (type 1 and 2), as the main structure of a floodwater spreading system which is susceptible to collapse due to flooding damages. In this research, one of the independent systems of FWS was selected in Kowsar research station in Gareh Bygone, Iran in order for evaluation of technical and economic analysis of drops’ collapse. The study is performed by direct observation and fieldwork. Results show that the main causes of collapses are erosion of embankment, piping of drop and instability collapse of side walls. Contrary to even of flood discharge of Bisheh Zard1, at flood events in 2003, the results show that the amount of destruction in an inclined drop is more than the vertical drop. Inclined drop 1 and vertical drops are the less and the most expensive, respectively. Therefore, inclined drop 1 might be recommended for being widely used due to maximum stability and minimum costs (the ration of 0.6 between the costs of inclined 1/vertical drops).