Assessment and Sensitivity analysis quantity of runoff and drainage system in coastal urban area by SWMM Model (case study:part of Bandar Abbas city)

Background and objectives: In urban catchment because of developed conditions, the amount of impervious area increases which tends to increase runoff volume, peak discharge rate and decrease of infiltration volume. Increase in impervious surfaces to reduce the influence on subsurface flow and base flow or flow of dry air is both concrete and natural channel. In Bandar Abbas city measured and recorded flood in the region is particularly important because of the lack of hydrometric station or any base to measure and record flood. The main objective of the study was evaluate the status of surface water collection system is part of Bandar Abbas city by SWMM model. Addition to investigating flood, weaknesses identified in the network to collect surface runoff Moreover, the critical parameters in the model were determined.
Materials and methods: in the first for runoff simulation and to determine sensitive point flooded was used of SWMM Model. The coefficient of determination (R2) and Nash Sutcliffe (NS) for calibration and validation the model were used in five events 2014/01/19; 2015/03/11; 2015/12/25; 2014/01/07 and 2016/01/03. Depth and velocity measured in outlet basin by current meter gauging. Also to determine sensitive point flooded of Bandar Abbas city used of way measured field with help Eshel. In order to sensitivity analysis were evaluated nine effective parameters in the model using Nash-Sutcliffe (NS).
Results: The results showed that the most sensitive Respectively parameters based on the coefficient NS impervious present area, Roughness coefficient impervious area, width, Storage the depth of impervious areas, sub basin areas, slope percent, Storage areas percent without surface, Storage the depth of pervious areas and Roughness coefficient pervious area. The results obtained from model calibration (respectively calibration average coefficient NS 0.75 and coefficient R2 between 0.83) showed good agreement with the observed data. Validation results (mean coefficient NS 0.79 and coefficient R2 between 0.92) showed high accuracy for this area. It was found flooding in some areas was due to lack of adequate capacity conduit. However In some places model confirms that sufficient channel capacities, There were flooding due to the blockage Rubbish is in these places.
Conclusion: The results evaluate showed discharge runoff simulation and estimated SWMM model has a good compliance (adapt ate).According to the ability of each sub-basin runoff simulation model and determine the critical points of this model is suitable to be used in city areas without Hydrometrics station. But the model must be calibrated. So we can use this model to predict the risk of flooding, design and estimate the amount and cost of drainage, urban coastal watershed management and prioritizing fixing the problem areas to be flooded.