Abstract:
Intensity-Duration-Frequency (IDF) relationship of rainfall amount is one of the
most commonly used tools in water resources engineering for planning
designing, and operation of water resources projects. The IDF allow for the
estimation of the return period of an observed rainfall event for different time
durations conversely, it may be used to estimate rainfall amount corresponding
to a given return period for different aggregation times. The objective of this
research is therefore, to develop operational IDF relationships for the SNNPR
state based on nineteen first class stations.
The annual maximum rainfall magnitudes of varying duration were collected
from rainfall charts and fitted to the probability distributions after which quantiles
estimated for different return periods based on the best fitted distributions.
Rainfall Intensities are then calculated and the parameters of the general
mathematical form of IDF were generated for each station. Three different
methods expressing rainfall intensities have been developed to the study area; methods expressing rainfall intensities have been developed to the study area;
the general mathematical form, curves relating Intensity-Duration-Frequency of
rainfall and the IDF maps.
To extract the intensity of rainfall of any duration and frequency at areas
farthest from the principal stations, the SNNPR State has been regionalized and
the regional IDF parameters and IDF curves are developed for the established
regions.
The result of this study can be used to all water professionals and designers on
the activities of water resources and other related disciplines with in the region
by supplying important information's on rainfall Intensity, Duration and
Frequency relationships.
