Low Impact Development

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LOW IMPACT DEVELOPMENT MODELLING TO RESTORE URBAN WATERSHED HYDROLOGY IN RAJKOT CITY

MS.VIDHI H. KHOKHANI,

M.E.[WREM] Student, Department Of Cvil Engineering,L.E.college morbi, Gujrat technological University, Gujrat

jainamv@gmail.com,

ABSTRACT: The effects of traditional development practices on the hydrologic cycle have been well documented. Increases in the impervious surfaces associated with urbanization have resulted in increased surface Runoff,decreased baseflow,changes in stream morphology, increased stream temperature, aquatic/riparian losss. The goal of this paper to widely explores concept of low impact development as an innovative approach to stormwater management and ecosystem protection that integrates hydrologic controls into every aspect of site design to mimic the predevelopment hydrologic.This paper presents low impact development modellingof Rajkot city and compare various LID modelby using Storm water Management Modelling system 5.0.Finally concluding Best Management Practice for stormwater management.

Keywords—Low impact development (LID),SWMM (stormwater management modelling) Bioretention,Grasses swales,Predevelopment,Infiltration trenches,Best Management Practices(BMP) .

I: Introduction
Low Impact Development is an innovative approach to stormwater management and ecosystem protection that integrates hydrologic controls into every aspect of site design to mimic the predevelopment hydrologic regime. It is not a growth management strategy nor does it rely heavily on density restrictions, rezoning, clustering or conservation measures. Instead, LID focuses on engineering the built environment to maintain ecosystem and hydrologic functions. LID uses new site planning and design principles and a wide array of micro-scale management practices. It is a powerful technology that allows development in a manner that preserves water related ecological functions and maintains development potential. The goal of LID is not to mitigate development impacts, but to recreate and preserve a watershed’s hydrologic cycle. The Stormwater management model EPA SWMM 5.0 is a “dynamic rainfall-runoff simulation model used for single event or long-term (continuous) simulation of runoff quantity and quality from primarily urban areas” (USEPA, 2009). The model is divided into four conceptual compartments atmosphere, land surface, groundwater, and transportion. Model is prepared and simulated for the single event rainstorm than it is calibrated and validated for the observed data. Then various model scenario is developed. LID stormwater management practices are capable of reducing the volume of urban runoff and thus have the potential to greatly reduce the size and cost of stormwater basins and conveyance systems (EPA, 2007). Additionally where conventional stormwater BMP’s struggle to address water quality issues, LID BMPs are robust. The filtration and infiltration of stormwater provided by many LID BMP’s have been shown to reduce dissolved pollutants, nutrients (Davis, Hunt, Traver, & Clar, 2009), and bacteria (Clary, Jones, & Urbonas, 2009). Moreover, the total volume reduction of stormwater - through the process of infiltration - is crucial to maintaining the natural flow regime of urban streams upon which the health of aquatic species depends. .

II: STUDY AREA
The study area is located almost entirely within the boundary of the Rajkot Watershed, and includes forested land , an industrial area surrounding and residential or urbanized areas on the Draft.Town.Planning.Scheme no 19 .Fig 1 shows location of Rajkot city and fig-2 shows area selected for study.The study area is divided into 9 small subcatchment and the drainage characteristics of catchment is derived by using SRTM (Shuttle Radar Topography Mission)data, A digital elevation model (DEM) with a resolution of 90 m SRTM data available on http://srtm.csi.cgiar.org/ were used.Figure 3 shows subcatchment area of watershed with...
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