Write short notes on depth area duration curves and intensity duration frequency curve
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Once the sufficient rainfall records for the region are collected the basic or raw data can be analysed and processed to produce useful information in the form of curves or statistical values for use in the planning of water resources development projects. Many hydrologic problems require an analysis of time as well as areal distribution of storm rainfall. Depth-Area-Duration (DAD) analysis of a storm is done to determine the maximum amounts of rainfall within various durations over areas of various sizes.
The preparation of DAD curves is done in following steps:
ADVERTISEMENTS:
1. Examine the rainfall records of the region in which catchment area under consideration is located. Also consider records of meteorologically similar regions. From it prepare a list of most severe storms with their dates of occurrence and duration.
2. For the listed severe storms prepare iso-hyetal maps and determine the rainfall values over the area of each isohyet (rainfall contour).
3. Draw on a graph curves connecting area and rainfall values for different durations say 1 day rainfall, 2 day rainfall, 3 days rainfall
The curves are called Depth-Area-Duration curves:
Use of DAD Curves:
Although most severe storm in the listed storms may not have occurred right over the catchment under consideration there is possibility of such occurrence. So from DAD curves 1 day, 2 day, 3 day rainfall depths for the catchment area of the proposed project are read. These give the rainfall depths when the storms are centered over the catchment.
The preparation of DAD curves is done in following steps:
ADVERTISEMENTS:
1. Examine the rainfall records of the region in which catchment area under consideration is located. Also consider records of meteorologically similar regions. From it prepare a list of most severe storms with their dates of occurrence and duration.
2. For the listed severe storms prepare iso-hyetal maps and determine the rainfall values over the area of each isohyet (rainfall contour).
3. Draw on a graph curves connecting area and rainfall values for different durations say 1 day rainfall, 2 day rainfall, 3 days rainfall
The curves are called Depth-Area-Duration curves:
Use of DAD Curves:
Although most severe storm in the listed storms may not have occurred right over the catchment under consideration there is possibility of such occurrence. So from DAD curves 1 day, 2 day, 3 day rainfall depths for the catchment area of the proposed project are read. These give the rainfall depths when the storms are centered over the catchment.
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