Design of Storm Drainage System for a new metropolis to be developed is the portion of overall substructure design of the undertaking. The design will include the independent storm drainage system for development country and its integrating with the hereafter storm drainage system. Purpose of survey The aim of the design of storm drainage system is to guarantee that there will be no deluging nearby the undertaking country site and dispatching the run-off off from the proposed site to the nearest interface point or sea in a minimal clip and in safe mode.
Thumping of storm H2O on roads and public countries will be minimized to let the public entree on the roads and public countries during the rain and after. Existing Conditionss There is no conventional storm drainage system dwelling of gimmick basins and pipe web within the undertaking bound. Codes and Standards Following Codes and Standards are used for set uping design standards: American Society of Civil Engineers ( ASCE ) – Manual and Report on Engineering Practice No. 37. Design and Construction of Urban Storm H2O Management Systems. prepared by Water Environment Federation. American Society of Civil Engineers.
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( ASCE Manuals and Reports of Engineering Practice No. 77 ) Design Criteria The undermentioned design standards will be used for the design of storm H2O drainage system Design Storm Frequency/Return Period The drainage systems in the metropoliss are designed to manage storms holding return periods runing from about one twelvemonth to five ( or ten ) old ages. depending on the value of the belongingss in the drainage country and the nuisance value of the implosion therapy. Design for 10 old ages is common in most metropoliss of the universe. Close Conduits 1- 50 twelvemonth storm – for design of a storm drain which will be located in a natural H2O class.
2- 25 twelvemonth storm – for design of a storm drain for a sub- division 3- 10 twelvemonth storm – for all other storm drain design Open Channels 100 twelvemonth storm – for design of channels located in a natural H2O class 25 twelvemonth storm – for design of route side channels used for deviating or taking surface H2O from main road right of manner. 10 twelvemonth storm – for all other unfastened channels design with sufficient free board to incorporate a storm of 50 twelvemonth frequence. Methodology for Estimation of Design Discharges The Rational Method The Rational Method is based on the simplification that the strength of rainfall is changeless throughout the continuance of storm.
Rainfall Intensity ( Magnitude ) Rainfall magnitudes matching to different return periods have been estimated Time of Concentration Design of primary systems. the clip of concentration may be calculated by Kirpich Formula Runoff Coefficient The overflow co-efficient “C” is the ratio of the maximal rate of overflow to the mean rate of rainfall in the country during the clip of concentration. Roughness Coefficient of Pipes and Channels Runoff Coefficient ( N ) that could be used in Manning’s Equation. Design of Storm Drains The storm drains will be designed for unvarying flow. The speed will be calculated based on the Manning’s Formula.
Speed of Flow Maximum and minimal speed of the flow needs to be considered Design of Close Conduits Close conduits are usually designed for the conditions of fluxing full. Design Depth of Flow Storm drains will be designed to flux full under extremum flow conditions. Gradient of Storm Drain Minimum gradient for a subdivision of the drain will by and large be taken to be the gradient necessary to fulfill the lower limit speed demands. Sizes of Drains Sizes of gimmick basin lead pipe and Main Drains in the system would be specified Manhole Dimensions Manhole size. form and dimensions need to be specified.
Catch Basins Location of the basins on chief streets would be reviewed so as to avoid implosion therapy and submerging of the roadway during rain storm. Discharge Quality Standards The quality of storm H2O to be disposed of into the canal / sea will run into the demands of Environmental Protection Standards Review of Master Plan Master Plan review gives an thought about storm drainage construct. Same standards will be used with little fluctuations. on the footing of which elaborate design of storm drainage system will be carried out. Proposed Concept Storm H2O drainage system comprises of two parts i. vitamin E.
for unfastened countries and roads. Storm H2O system for unfastened countries consists of sheet flow on land. so intercepted by Gratings. Interceptors. Catch Basins. and Curb Inlets and drained to the selected locations. Strom Drainage System is required to avoid deluging on the roadways. to supply traffic safety and to protect the route installations. Rapid remotion of storm H2O from the traveled manner minimizes the status which consequences in the phenomenon of aquaplaning. Catchments Areas The country lending to any point under consideration in a storm drainage system will be determined by accurately mensurating from the maps.
Boundaries of the sub-catchments countries are established by its proposed contours. References 1. Engman. E. T. 1986. Roughness Coefficients for Routing Surface Runoff. Journal of Irrigation and Drainage Engineering. ASCE 112 ( 1 ) : 39-53. 2. Hawkynss. R. H. . A. T. Hjelmfelt. and A. W. Zevenbergen. 1985. Runoff Probability. Storm Depth. and Curve Numbers. Journal of Irrigation and Drainage Engineering. ASCE 111 ( 4 ) : 330-340 3. Maryland Department of the Environment. 1997. Draft: Maryland Storm H2O Design Manual. Volume One. Prepared by: Center for Watershed Protection. Inc.
