Comprehensive Flood Control And Mitigation Systems

Abstract

Many large cities are located in flood plains and lowland areas such as Bangkok, Taipei, Jakarta, Shanghai, and Osaka, etc. These cities are highly urbanized and populated. They are flooded often due to heavy rainfall, overbank flow, insufficient flood drainage, land subsidence and lack of effective flood control measures. Flooding periods in lowland areas normally prolong over a long period of time and in many cases have serious consequences on socio–economic and environmental conditions. Flood control and protection methods can be categorized into two major components namely: structural measures and non–structural measures. Structural flood control measures may be over–designed or not fully effective if their design or operation do not consider non–structural flood control measures. Therefore, a comprehensive flood loss prevention and mitigation system should be developed incorporating both structural and non-structural flood control measures. However, it should be realized that in general, structural flood control measures mainly contribute to the overall effectiveness of the comprehensive flood loss prevention and mitigation system. Structural flood control measures include dams, reservoirs, flood bypass channels, river dikes, tidal barriers, flood control gates and polders, etc. Figures 9.1, 9.2 and 9.3 show the structural flood control measures of the Bicol river basin, the Philippines; of Bangkok, Thailand and of Jakarta, Indonesia (Tingsanchali 1988b). Non–structural flood control measures include land use planning and control, flood proofing, flood forecasting and warning, etc. Given a design hydrological condition, the geometrical dimensions of selected flood control measures can be determined by using mathematical models or physical hydraulic models. Both types of models have to be calibrated using measured field data. After model calibration, the calibrated model is applied to determine the hydraulic effectiveness of the flood control measures on flood flow conditions. With the advancement of computers, mathematical models are now being widely used with more flexibility, higher 192 193 194accuracy and less economical implications. Figure 9.1 Proposed flood control scheme and mathematical model for flood flow simulation, Bicol river basin, Philippines. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203748596/9a472236-b116-45b3-8045-42b143e866fa/content/fig9_1.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> Figure 9.2 Proposed flood control scheme of Bangkok (Chao Phraya-2 Project), Thailand. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203748596/9a472236-b116-45b3-8045-42b143e866fa/content/fig9_2.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> Figure 9.3 Existing and proposed flood control scheme for Inner Jakarta, Indonesia. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203748596/9a472236-b116-45b3-8045-42b143e866fa/content/fig9_3.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/>