How do you find the ordinates of the unit hydrograph?
By definition, Unit Hydrograph is a direct runoff hydrograph resulting from the unit depth of effective rainfall. So, the ordinates of required UH can simply be obtained by dividing the ordinates of Direct Runoff Hydrograph by the equivalent depth of total direct runoff as shown below.
What is a hydrograph ordinate?
The unit hydrograph is a well-known, commonly-used empirical model of the relationship of direct runoff to excess precipitation. The ordinates of a direct-runoff hydrograph corresponding to excess precipitation of a given duration are directly proportional to the volume of excess.
When hydrograph is called as a unit hydrograph?
The unit hydrograph is a hydrograph with a volume of 1cm runoff resulting from a rainfall of specified duration and a real pattern.
What does a 2 hour unit hydrograph correspond?
As observed in the table, the duration of the effective rainfall hyetograph is 2 hours. Thus, D = 2 hours, and the Unit Hydrograph obtained above is a 2-hour Unit Hydrograph….
| Time (h) | Observed Hydrograph (m3/s) |
|---|---|
| 2 | 300 |
| 3 | 700 |
| 4 | 1000 |
| 5 | 800 |
What is 3 hour unit hydrograph?
A unit hydrograph can be defined as the hydrograph of direct runoff resulting from one unit depth (1 cm) of rainfall excess occurring uniformly over the basin for a specified duration. The unit hydrograph is the unit pulse response function of a linear hydrologic system.
What is hyetograph and hydrograph?
1. A hydrograph is graphically plot of discharge of a natural system for river versus time. A hyetograph is a plot of intensity of rainfall against the time interval it is usually represented buy a bar chart. 2.
How do you make a unit hydrograph?
- Step 1: Select Appropriate Precipitation Event.
- Step 2: Remove Baseflow Contribution.
- Step 3: Calculate Volume of Quick-Response Runoff ”
- Step 4: Determine Excess Precipitation Depth for the Basin.
- Step 5: Adjust The Quick-Response Hydrograph to Represent 1 Unit of Excess.
- Step 6: Determine Duration.
- Final Unit Hydrograph.
How do you select a suitable unit hydrograph to calculate peak flows for a given catchment area?
Use of this formula tends to over-estimate flood peaks in temperate, flat and permeable areas; for these, a simple triangular unit hydrograph, with a base of 2.5 times the time to its peak, should suffice. Its peak flow is 2.2/Tp m3/s for each km2 of catchment for every 10 mm of effective rainfall.
In what way are all the precipitations measured?
In what way are all the precipitations measured? Explanation: All forms of precipitation are measured on the basis of vertical depth of water which would accumulate on the level surface if all the precipitation remained where it fell. The rainfall is usually measured with rain gauges.
What physical factors affect the shape and timing of the unit hydrograph?
The time to peak is largely determined by drainage characteristics such as drainage density, slope, channel roughness, and soil infiltration characteristics. Rainfall distribution in space also affects the time to peak.
Why is unit hydrograph necessary?
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.
How do you plot a unit hydrograph?
- Step 1: Select Appropriate Precipitation Event.
- Step 2: Remove Baseflow Contribution.
- Step 3: Calculate Volume of Quick-Response Runoff ”
- Step 4: Determine Excess Precipitation Depth for the Basin.
- Step 5: Adjust The Quick-Response Hydrograph to Represent 1 Unit of Excess.
- Step 6: Determine Duration.