The time of concentration for a given storm water drain is "the total time required by the flow to reach to the maximum limit". It generally consists of two parts; viz. (i) The Inlet Time or Overland Flow Time or Time of Equilibrium (T): The time taken by the water to flow overland from the critical point upto the point [...]
Following procedure is followed in the determination of the maximum runoff of a large locality: (i) The total area of a the locality is divided into smaller units, from where the water flows in various inlets. (ii) The time-area diagrams for each area so divided is obtained and plotted. (iii) Now the cumulative time-area diagram is plotted step by step. [...]
Fig. 4.5 illustrates the group of areas from where the storm water flows towards the inlets I1, and I2, Let A, B, C, D and E be the areas, whose storm water enters the inlet I1, and area F on both the sides of the sewer whose storm water enters the inlet I2. Let T1 be the time required for [...]
Generally there are two methods by which the quantity of storm-water is calculated: 1. The Rational Method 2. Empirical Formulae Method. In both the above methods, the quantity of storm water is a function of the area (in hectares): the intensity of rainfall and the coefficient of runoff. The coefficient of runoff or the maximum rate of runoff mainly depends [...]