International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 04 | Apr -2017
p-ISSN: 2395-0072
www.irjet.net
Hydrologic Computations of SCS-CN, Rational, Area velocity and Tc Methods for Quantifying the Forest Surface Water Runoff - A case study in Sirumalai hill environs of Sathiyar Reservoir, Madurai, Tamil Nadu, India K.Chandramohan1, R.Vijaya2
Ph.D Research Scholar, Assistant Professor, UGC-Human Resource Development Centre, Madurai Kamaraj University, Madurai, Tamil Nadu, India. ---------------------------------------------------------------------***--------------------------------------------------------------------1.INTRODUCTION Abstract - Majority of surface water flow data are needed 1
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for engineers, planers, policy makers and other environmental developers. In this regard, surface water quantification is an essential study. Surface water measurement can be done by various methods in order to know the surplus or shortage of water availability and hence the hydrologic calculation is an important factor in the surface water study. Surface runoff is the water flows from the elevated area to the low lying area and it makes the land as wetland in which it flows. The main objective of the study is to quantify the surface water in Sirumalai hill environs of Sathiyar Reservoir, Madurai, Tamil Nadu using various mathematical calculations and methods. Several measuring techniques which involve mathematical models and equations are available to find the surface water volume and flow rate. Here, the rational method which is followed worldwide is used to find out the surface water quantity. In this rational method, many parameters like runoff coefficient, intensity of rainfall, area of drainage etc., were adapted. Runoff (RF) calculation was carried out by using potential abstraction, soil Curve Number (CN) and intensity of rainfall, while the runoff value was calculated by Soil Conservation Service (SCS). This research work will clearly deals with two major components of water balance of rainfall intensity and runoff. Field dada collection was carried out for homogeneous micro watersheds of the study area based on the slope and rainfall intensity at the sites using same tools and techniques. Water states were measured by Syman’s raingauge meter and Bucket method for water quantification in direct field measuring for rainfall intensity and flow rate respectively. These values are reclassifying and try to extend to find other methods of Thiessen polygon, SCS CN, Rational method of runoff coefficient and Time of Concentration. Key Words: Water balance, Runoff, Coefficient, Hydrologic Calculation, Surface, Runoff, SCS CN, Thiessen polygon, Rational method, Time of Concentration (Tc), Area velocity, Remote Sensing, GIS, GPS …
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In general, storm water runoff can be described as the flow of water through rainfall interaction with the land. The calculation of runoff coefficient will vary due to different types of physiographic features like vegetation interception, soil infiltration, slope, geomophological structure etc. The rainfall events can also be varied in a same period. These events produce different runoff volumes and peak discharge. Rational method was developed by Kuichling (1889) to estimate the channel runoff. Water-resources planning typically include identifying alternatives and ranking the alternatives based on specified criteria. The purpose of the hydrologic study using the present techniques is carried out for estimating peak discharges of runoff water. When actual flow data has been transformed into a normal variable by using the logarithmic transformation, then the prediction of runoff value will be easy (Lawrence K. Wang, 2014). The earth surface will be completely soaked when the micro watershed area is fully covered by flood water (Slobodan P. Simonovic 2009) then the surplus was drained into the canals. The Rational Method is widely used to calculate the peak storm water runoff rate for a variety of storm water management applications. If the planners have associated flow data in such situation, engineers use this prediction equations called flood frequency equation to predict the flood value. Mathematical calculation of hydrologic parameters also referred as hydrological models (Kite.G.W and Pietroniro.A, 1996). These mathematical models can be applied to other micro watershed regions to plan the construction of highway, cableway, bridge, electricity, ice cover, or boat house and other constructions cross over the stream and river if the runoff value is known. Water and sediment control practices should be made easy and control measurement should be fixed on more possible places (Haan.C.T. et al 1994).
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