A Simple Model for determining flood hazard areas

Determination of the submergible area by flood provides a fundamental tool for reducing flood risks. Therefore, in this research, flood spreading modeling was designed using web-based software with the capability of zoning submerged areas by Google Maps DEM Data. For this purpose, at the first, a specified interval of a river is selected on the map. Then, at each selected section, the maximum cross-sectional area for passing flow is calculated. Then, based on the average of the cross-section area for the total interval and the physical properties of the selected river interval, the maximum flow rate is calculated. For this flow rate, the safe area of the flood is marked on the map. For a greater flow rate, the software determined the areas at risk of flooding, and ultimately the flood risk map is specified. For example, the software was applied for a seasonal river in Shiraz, which sinks to the Maharlu Lake with satisfactory results. Afterward, the October 2011 flood event of Ayutthaya River in Thailand was investigated, where satellite images of the flood-affected areas were available. Investigation of the satellite image of this flood along with the survey of topographic maps of the river route indicated peak discharge of the flood was 4113.01 m3/s, which differed as 2.1 percent as compared to a record of 4200 m3/s (real measured peak flow). If the flood occurs with the current situation in the area, the flooded area decreased by 17.63% compared with the submerged area in 2011. Furthermore, simulation of the March 2019 Shiraz Flood by the model was in good agreement with the report of the Special Committee of 2019 Iran Floods.