URBAN FLOOD DRAINAGE PLANNING,

Abstract

Hydrology of urban areas is dominated by preponderance of impervious surfaces and presence of manmade drainage channels. Engineering objective when dealing with urban hydrology is to provide for control of peak flows and maximum depths at all locations within the drainage system. Rational formula and SCS method have been explained with illustrative examples to provide an understanding of urban hydrology. Storm Water Management Model (SWMM) is a rainfall runoff simulation model which can be used for single event or long-term (continuous) simulation of runoff quantity and quality from primarily urban areas. Only runoff component and routing portion of the SWMM have been explained and applied in the present study. SWMM . 5 is the latest version of software which has been downloaded from interne and studied in detail. Two application studies are provided in this dissertation. Both the studies are for simulating single event storm runoff. First study deals with existing drainage system of IIT Rorrkee Campus. Field survey and filed data have been collected to provide properties of subcatchments and existing drainage as per requirement for use of SWMM. Even though it is combined sewer system in IIT Roorkee campus, only 50 year storm runoff drainage has been considered. It is found that existing layout and capacities are adequate to handle 50 year storm event. It is possible to make further improvement in simulation study of IIT Roorkee campus by increasing the number of subcatchments (through subdivision) and incorporating more accurate properties of subcatchments, channels based on field measurements. Second study deals with planning of drainage system for proposed thermal power plant site. Design storm for 100 year return period has been considered for planning of drainage at Thermal Power plant site in consideration of the importance of the power plant. Microscopic approach has been attempted for study of subcatchments runoff. The proposed layout, size and slope of drainage channels is based on several simulation trials and it is found to be hydraulically efficient. Computer based Storm Water Management Model can be used in several practical applications. This study provides an understanding of urban hydrology and microscopic approach to planning of urban drainage. The two case studies illustrate procedure for achievement of this engineering objective of urban hydrology i.e. control of peak flows within the drainage system.