### What is the unit hydrograph method?

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 is the difference between hydrograph and unit hydrograph?

Basically, the unit hydrograph is a multiplier, converting rainfall to runoff. A unit hydrograph is a hydrograph and thus its multiplying effect varies with time, producing from rainfall a time distribution of surface runoff. A unit hydrograph only measures direct surface runoff.

### How do you calculate ordinates of unit hydrograph?

Let us first define number of equations. There are 3 pulses of rainfall so M = 3. There are 13 pulses of observed direct runoff so n = 13. The number of unit hydrograph ordinates is therefore, n – m +1 = 13 – 3 + 1 = 11 ordinates.

### When hydrograph is called as a unit hydrograph?

5. When is the Hydrograph called as a unit hydrograph? Explanation: If the rainfall distribution in the storms is similar with respect to time and area, the ordinate of each hydrograph will be proportional to volume of runoff.

### What is a hydrograph give an example?

ADVERTISEMENT. Hydrographs are charts that display the change of a hydrologic variable over time. Here are several examples from the US Geological Survey’s gaging station on the Tioga River near Mansfield, Pennsylvania.

### What is a 2 hour unit hydrograph?

Thus, D = 2 hours, and the Unit Hydrograph obtained above is a 2hour Unit Hydrograph. Therefore, it can be used to predict runoff from precipitation events whose effective rainfall hyetographs can be represented as a sequence of uniform intensity (rectangular) pulses each of duration D.

### How is hydrograph measured?

A hydrograph is a graph showing the rate of flow (discharge) versus time past a specific point in a river, channel, or conduit carrying flow. The rate of flow is typically expressed in cubic meters or cubic feet per second (cms or cfs).

### What does a hydrograph tell?

A hydrograph is a graph showing stage, discharge, velocity, or other properties of water flow with respect to time. When the stage is plotted against time, the graph is a stage hydrograph (which is the form of a stream gage record).

### What is annual hydrograph?

Annual hydrograph represents the variation of daily or weekly or 10 daily mean flow over a year. Flood hydrograph or simply hydrograph represents stream flow due to a storm over a catchment. Each of these types has specific applications.

### 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.

### What are the limitations of unit hydrograph?

LIMITATIONS OF A UNIT HYDROGRAPH: i)Unit hydrograph method is not applicable to areas with a major portion of storm precipitation being on form of snow. ii)Principle of time in-variance sometimes does not hold as the basin characteristics will chabge with man made adjustments as well as seasons.

### What makes a hydrograph flashy?

A hydrograph is a graph of the flow in a stream over a period of time. Reading horizontally to the left, you can determine the discharge of the stream for that date. “Flashy” To say that a hydrograph is flashy means that the graph depicts sharp vertical jumps and equally steep vertical declines.

### What is a storm hydrograph and what factors can impact it?

The amount precipitation can have an affect on the storm hydrograph. Heavy storms result in more water entering the drainage basin which results in a higher discharge. The type of precipitation can also have an impact. The lag time is likely to be greater if the precipitation is snow rather than rain.

### What causes short lag time?

Slope – steep slopes lead to rapid water transfer and shorter lag times. Gentle slopes slow down water transfer making the lag time longer. Drainage basin shape – a high density basin has more streams and rivers which speed up water transfer and shorten lag time.

### How can I get lag time?

Time = Distance / Speed

So, the lag time difference between the two vehicles (10 hours – 5 hours) is 5 hours. What would the lag time be if the distance traveled were 500 miles? Vehicle A would take 10 hours to travel 500 miles, but Vehicle B would take 20 hours. The lag time here is 10 hours.

### What is a lag time?

Lag Time is the delay between the first and second activities. For example, the duration of the first activity is three days and two days for the second activity. After completing the first activity, you wait for one day, and then you start the second. Here, we say that the Lag Time is one day.

### What factors increase lag time?

The type of precipitation can also have an impact. The lag time is likely to be greater if the precipitation is snow rather than rain. This is because snow takes time to melt before the water enters the river channel. When there is rapid melting of snow the peak discharge could be high.

### Why is there a lag time?

The peak discharge is the time when the river reaches its highest flow. There is a delay because it takes time for the water to find its way to the river. This is called lag time. The normal (base) flow of the river starts to rise when run-off, ground and soil water reaches the river.

### How does deforestation affect lag time?

2. Deforestation (the removal of trees) can increase soil erosion, reduce interception and increase flood risk. Ploughing of the soil breaks it up and allows more infiltration. This reduces peak discharges and increases lag times.