Managing Flood Flows for Crop Production Risk Management with Hydraulic and GIS Modeling: Case study of Agricultural Areas in Shariatpur

Shariatpur District, under Dhaka division with an area of 1181.53 sq km, is mainly surrounded by the two big rivers, the Padma at north and the Meghna at eastern side. Also, the Arial Khan River is located at the south western side of the district. When the Padma and the Meghna Rivers attain peak flood levels simultaneously, this district faces devastating floods. These floods have a destructive effect on agriculture especially on Aman (June- September) variety at optimum level of flood depth but also have a positive impact on next year's Boro (December- march) production due to sedimentation by the previous year's flood. So there is a scope of managing flood flows which ensures the optimum level of flood depth that promotes the crop production risk management. The present study provides a method for flood management aiming to crop production risk management. In this study, inundation maps have been produced using hydrodynamic model HEC-RAS and HEC-GeoRAS extension of ArcGIS9.2. Then calculation of optimal flood depth for crop production risk management has been done using some sophisticated statistical analysis. Finally, volume of water above the optimal flood depth has been calculated using GIS model with ArcGIS 9.2 and based on this, proposed some ways of flood flows management which ensure the crop production risk management. The study findings show that, the optimal flood depth is 1.85m (msl) in where Boro production would be safe and Aman production would face about 200 ton/yr loss, we can called this condition as crop production as farmers get more return from Boro variety. This study also find two equations that provide estimation of Mawa discharge depending on two upstream stations (Hardings Bridge and Bahadurabad Ghat) and targeted discharge of Mawa that needs to release from Mawa to the study area for ensuring the optimum flood depth.