Analysis of Rainfall Intensity-Duration-Frequency Relationship for Rwanda

Abstract

Global atmospheric and oceanic perturbations and local weather variability induced factors highly alter the rainfall pattern of a region. Such factors result in extreme events of devastating nature to mankind. Rainfall Intensity Duration Frequency (IDF) is one of the most commonly used tools in water resources engineering particularly to identify design storm event of various magnitude, duration and return period simultaneously. In light of this, the present study is aimed at developing rainfall IDF relationship for entire Rwanda based on selected twenty six (26) rainfall gauging stations. The gauging stations have been selected based on reliable rainfall records representing the different geographical locations varying from 14 to 83 years of record length. Daily annual maximum rainfall data has been disaggregated into sub-daily values such as 0.5 hr, 1 hr, 3 hr, 6 hr and 12 hr and fitted to the probability distributions. Quantile estimation has been made for different return periods and best fit distribution is identified based on least square standard error of estimate. At-site and regional IDF parameters were computed and subsequent curves were established for different return period. The moment ratio diagram (MRD) and L-moment ratio diagram (LMRD) methods have been used to fit frequency distributions and identify homogeneous regions for observed 24-hr maximum annual rainfall. The rainfall stations have been divided into five homogeneous rainfall regions for all 26 stations. The results of present analysis can be used as useful information for future water resources development planning purposes.

Inter-annual variability of March to May rainfall over Tanzania and its association with atmospheric circulation anomalies

“…The variability of rainfall has shown a significant impact on disaster management efforts and growth of the economy of peasant people in sub-Saharan Africa countries (Wagesho & Claire, 2016). Over East Africa, the abnormal events of atmospheric phenomena observed in recent years, were associated with late onset and early withdraw of MAM rainfall over the region (Mugalavai et al, 2008;Camberlin et al, 2009).…”

Rainfall induced erosion of soils used in earth roads

“…The pressurised rain simulator suitable for laboratory works was developed to give rainfall intensities ranging from 20 mm/hr to 151 mm/hr. A rain intensity of 30 mm/hr recurrent for more than 50 min every two years in tropical countries was taken as the worst-case scenario [12,13]. The rain simulator was constructed using 15mm x 1.5mm BARRIER PE-X pipes according to [14].…”

Regional Design Storm and Flood Modelling—Risk Implications in Ungauged Catchments

“…GEV was found to be a robust model for the Limpopo basin system through regional analysis [24]. Even though the L-Moments technique [25] of parameter estimation was used in [5] [24], in this study we used the method of moments to derive the higher moments of scale and shape parameters of this distribution. The location parameter that is associated with the mean of the flood series was estimated from the regional mean values scaled to catchment area of the respective watersheds considered in the study.…”

“…These curves allow one to estimate the design storm, provided that historical rainfall extremes are available using scaling and stochastic models [2] [3] [4]. When observed at-site rainfall data are lacking, the estimation of the design storm may be conducted by using regional frequency analyses for infrastructure design [5] [6] [7]. Intensity-duration-frequency (IDF) models have been tested for their application in infrastructure design as well as for climate projections under non-stationary condition as a result of climate change [8] [9].…”