Question

Provide a brief review, at least 500 words, on unit hydrograph derivation methods. Acknowledge the used references and provide a list of references.

Answer 1

derivation of unit hydrograph

step 1 from the given flood hydrograph deduct the base flow to obtained direct runoff hydrograph

step2 determine volume of direct runoff hydrograph

step 3 divide the value of direct runoff by catchment area to get excess rainfall.

step 4 divide ordinate of DRH by the excess rainfall to get UH.

UNIT HYDROGRPH OF DIFFERENT DURATION CAN BE SOLVED BY 2 METHODS

1. METHOD OF SUPERPOSITION

2. S CURVE METHOD

METHOD OF SUPERPOSITION

suppose we have D-hr unit hydrograph and we want to develop a unit hydrograph of nD hr where n is an integer then superposition method is best suited

1. we have a unit hydrograph of D-hr or let D=3 and we want to find 6hr unit hydrograph then

2. draw unit hydrograph of D-hr and another unit hydrograph of D-hr is drawn by legging by D-hr (3-hr), simple maths we already have 3 we want 6 so we just add 3 more 3+3=6

3. add the ordinate of both the hydrograph give us unit hydrograph of 2 unit of 2D-hr.

4. divide the ordinate by 2 gives unit hydrograph of 1 unit of 2 D-hr.

FOR MORE CLARITY PREFER MY HANDWRITTEN NOTES

in above example. try to explain how uh depend on linear response assumption, second assumption given below