The methods employed in the work include; the S-curve or summation curve, instantaneous unit hydrograph, and synthetic unit hydrograph. S-curve is the hydrograph of direct surface discharge that would result from a continuous succession of unit storm producing 1cm tr-hr (duration of the unit hydrograph (hr)).

What are the methods of unit hydrograph?

The methods employed in the work include; the S-curve or summation curve, instantaneous unit hydrograph, and synthetic unit hydrograph. S-curve is the hydrograph of direct surface discharge that would result from a continuous succession of unit storm producing 1cm tr-hr (duration of the unit hydrograph (hr)).

What is S curve hydrograph?

The hydrograph, for a given river basin, that would theoretically result from a continuous, constant excess rainfall rate per specified period T resulting in a runoff volume of 1.00 unit depth (e.g., 1.00 cm or 1.00 in.) over the basin for each period T.

What is S curve hydrograph and how it is constructed?

A ‘S’ hydrograph is nothing but a hydrograph generated by a continuous effective rainfall occurring at an uniform rate for an indefinite period. It is called ‘S’ hydrograph because the shape of the hydrograph comes out like alphabet ‘S’ though slightly deformed.

What is the rational method in hydrology?

The Rational Method expresses a relationship between rainfall intensity and catchment area as independent variables and the peak flood discharge resulting from the rainfall as the dependent variable. It has been used for over 150 years, and known as the Rational Method for nearly 100 years.

What is Snyder unit hydrograph?

The synthetic unit hydrograph of Snyder (1938) is based on relationships found between three characteristics of a standard unit hydrograph and descriptors of basin morphology. The hydrograph characteristics are the effective rainfall duration, tr, the peak direct runoff rate, qp, and the basin lag time, tl.

What are unit hydrographs used for?

A unit hydrograph shows the temporal change in flow, or discharge, per unit of runoff. In other words, how the flow of a stream will be affected over time by the addition of one unit of runoff. The unit hydrograph is a useful tool in the process of predicting the impact of precipitation on streamflow.

What are the methods of estimating design flood?

Common approaches for estimating a design flood are based on: (i) hydrological methods such as continuous simulations with rainfall–runoff models, or (ii) statistical methods, such as the fitting of a probability distribution function to a record of annual maximum values.

What is the meaning of s-curve?

An S-Curve’s definition is a mathematical graph that represents all of the data for a project. It’s called an S-curve because of the graph’s striking similarity to the 19th letter of the alphabet.

What is Kirpich equation?

Kirpich equation is an empirical equation used to determine the time of concentration in runoff hydrograph and it is given as: t = 0.0194 L 0.77 S − 0.385. Where, t = time of concentration in minutes. L = the maximum length of water travel in m.

What is the application of unit hydrograph?

The Unit Hydrograph (UH) technique is widely used for runoff estimation, especially for determining peak discharges. In this paper, a geomorphologically based UH has been applied. Its most remarkable characteristic is that it includes the watershed structure in its formulation.

Why rational method is used?

What is the rational method formula?

The Rational method predicts the peak runoff according to the formula: Q=CiA, where C is a runoff coefficient, i is the rainfall intensity, and A is the subcatchment area. This formula is applicable to US or metric evaluation, as long as consistent units are employed.

What is Muskingum method?

The Muskingum method is a hydrological flow routing model with lumped parameters, which describes the transformation of discharge waves in a river bed using two equations.

What was proposed by Snyder?

Snyder proposed a relationship with which the total time base of the UH may be defined. I nstead of this relationship, the program uses the computed UH peak and time of peak to find an equivalent UH with Clark’s model (see the next section).

What is the theoretical number of unit hydrographs?

infinite
Explanation: The number of unit hydrographs for a given basin is theoretically infinite. This is because there may be one unit hydrograph for possible duration of rainfall and every possible distribution pattern of rainfall in the basin.

How do you calculate S-curve?

There are a number of equations that can generate an S curve, the most common is logistics function with the equation (in Excel notation): S(x) = (1/(1+exp(-kx))^a is the simple form of the equation, where the minimum value is 0 and the maximum value is 1, k and a both >0 and control the shape.