Flood Mitigation by Structural Method using Optimization Technique
Floods occurs in river or water bodies when the flow rate exceeds the capacity of the river channel or water body, particularly at bends or meanders in the waterway. Floods often cause damage to homes and businesses if they are in the natural flood plains of rivers. Floods can be managing and control by using structural and non-structural flood mitigation alternatives. By choosing best alternative, floods can be controlled in proper way. Flood mitigation involves the managing and control of flood water movement, such as redirecting flood run-off through flood walls and flood gates, rather than trying to prevent floods together. For selection of best alternative, dynamic programming is to be used for optimization technique. This selection is to be done on the basis of functional, environmental, social, economic and constructability. Dynamic Programming is decision making tool which gives best decision from the available source. In case study of Mithi River, Mumbai, catchment area is divided into four sub catchments. Discharge and depth of water for different rainfall intensity varying from 25 mm/hr to 225 mm/hr is determined by using SWMM 5.1 software for different catchment. Depth of flood is determined for that particular catchment by subtracting embankment depth from depth of water. According to the depth of flooding water height of retaining wall for that particular catchment for different rainfall intensity varying from 25 mm/hr to 225 mm/hr is to be decided. Height of retaining wall for catchment 1, 2, 3 and 4 of rainfall intensity 225 mm/hr are 3m, 9m, 15m and 25m respectively. Keywords- Catchment, Flood Mitigation, Structural alternative, Mithi River, SWMM 5.1, Optimization, Dynamic programming. I. INTRODUCTION Extreme rain events have always been a problem and a challenge in the urban society. When they occur in urban areas the consequences can be striking with severe flooding and damage to properties and infrastructure. Flooding events cause economic, social and environmental damage and lives loss. Flood hazard as part of the flood risk management can be defined as probability that flood prone area will be inundated for a given period of time with a specific return period. Flood modeling is a relatively new approach which is widely used for flood hazard, and risk assessment. Flood control measures aimed at lowering the vulnerability of people and their property include list of means, i.e. river engineering works, such as dams, flood walls, embankments, or river training works, retention polders. Flood control measures are essential in a watershed for reduction of flood damage. In planning of various structural and non- structural measures for flood control in a basin such as improvement of drainage network to increase carrying capacity, increase of the vegetation cover, etc., it is essential to carry out analysis to understand the impact of such measures in flood damage reduction and various scenario analyses are required to choose the best alternative. In such analysis, mathematical models can be viewed as a useful decision support system for planning of flood control measures. While planning, design, construction and operation of most structural measures can be done using definite mechanisms, the decisions of non-structural measures, especially flood forecasting and warning, are complex and are not uniquely defined. Therefore, such decisions require the aid of mathematical model results, and require both quantitative and qualitative decision modeling steps. Thus, these decisions can be effectively obtained through the use of a Dynamic Programming. The role of optimization in flood mitigation has increased substantially. The Dynamic