Use of the Unit Hydrograph The UHs establish a relationship between the ERH and DRH for a catchment They are of great use in i. The development of flood hydrographs for extreme rainfall magnitudes (for use in the design of hydraulic structures) ii. Extension of flood flow records based on rainfall records iii. Development of(…)

UNIT HYDROGRAPHS OF DIFFERENT DURATIONS • Ideally ,unit hydrographs are derived from simple isolated storms and if the duration of the various storms do not differ very much (within a band of + or – 0.20D), they would all be grouped under one average duration of D hours • Unit hydrographs of different durations, if(…)

DERIVATION OF UNIT HYDROGRAPHS 1. A number of isolated storm hydrographs caused by short spells of rainfall excess, each of approximately the same duration (0.9 to 1.1D h) are selected from a study of continuously gauged runoff of the stream 2. For each of these surface runoff hydrographs, the base flow is separated 3. The(…)

UNIT HYDROGRAPH • Very often it is required to predict the flood hydrograph resulting from a known storm • A large number of methods are available to solve this problem • Unit Hydrograph Method is the most popular and widely used method for predicting flood hydrograph resulting from a known storm • First suggested by(…)