EXPLANATION:A common method of Hydrologic channel routing is Muskingum method, in which the channel storage in a reach is expressed as a function of both inflow and outflow discharge.S = k [x Im – (1 - x)Qm]Where, s = Storage in a channel reachI = Inflow DischargeQ = Outflow Dischargek → COEFFICIENT known as storage time coefficient. It was unit of time, it is approx. equal to time of travel of flood wave through the channel reach.x → Weightage factor. Its range series from 0 to 0.5For naturally occurring channels m = 1, Hence the equation becomesS = k [x I – (1 - x)Q]For x = 0, storage is only a function of outflow discharge. Such RESERVOIRS are also known as Linear Reservoir. Flood routing is the technique of determining the flood hydrograph at a SECTION of a river by utilizing the data of flood flow at one or more upstream sections. There are two broad categories of routing:-1. Reservoir routing:-Level pool Routing is assumed i.e. the water level is assumed parallel to the channel bed.In level pool routing,(1) Storage is a function of height of water level i.e. S = f(h)(2) Outflow discharge is a function of water surface elevation. i.e. Q = f(h) Methods of Reservoir routing:(a) Modified pul’s method (Graphical method)(b) Goodrich metod (Graphical method)(c) Standard 4th order Runga – Kutta method (Universal method)2. Channel routing:-If the flow were uniform THROUGHOUT, the water surface line would wave been parallel to channel bed. However because of non-uniform condition due to flood, there will be water level which will not be parallel to channel bed.The volume of water stored in a channel reach is comprised of:Prism storageWedge storage A variety of routing methods are available and they can be broadly classified into two categories:(i) Hydrologic routing (ii) Hydraulic routingTypes of flood routing:(1) Hydrologic/lumped routing:Discharge is taken as a function of time.Continuity equation is used. (2) Hydraulic Routing/Distributed Routing:Discharge is taken as a function of time and space.Both continuity and momentum equation are used.