Browsing by Author "Nyadawa, Maurice O."

Now showing 1 - 8 of 8
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    Publication
    Comparative assessment of landslide susceptibility by logistic regression and first order second moment method: Case study of Bujumbura Peri-Urban Area, Burundi.
    (Journal of Engineering Research and Application, 2018-08-24) Shirambere, Gervais; Nyadawa, Maurice O.; Masekanya, Jean pierre; Nyomboi, Timothy
    Several landslides incidents in the Bujumbura region are reported regularly by independent sources. However, few studies on the causes in the region have been conducted and no record of susceptibility map at a regional exists. In this study, two different approaches are applied to map landslide susceptibility in the region. The physical approach is based on mohr-coulomb failure criterion and is applied using a probabilistic approach, the first order second moment method. The statistical approach is based on logistic regression. The study has two objectives: (i) to map landslide susceptibility in the region and (ii) to compare the results of the different approaches. Applying the two approaches in a GIS framework, two susceptibility map are produced. The accuracy of the two models is independently assessed using ROC and AUC curves. A comparative analysis of the results is conducted and the results shows a fair spatial correlation. The susceptibility maps are compared using rank differences and ArcSDM and a spatial comparison map of susceptibility levels is produced.
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    Publication
    Estimating Transmission Losses in the Main Channel of River Tana, Kenya
    (J-Stage, 1997) Nyadawa, Maurice O.; Kobatake, Shigeki; Ezaki, Kazuhiro
    This study has presented correlation equations thought to define channel loss in River Tana in Kenya. Modified Tank Model is used to transfer runoff information from gaged basins to ungaged ones in the study area. The study has revealed that channel loss has two step functions corresponding to flow rates below 800m3/s and larger values.
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    Publication
    Generalized characteristics of intense rainfall and peak discharges in Athi basin, Kenya
    (JSHWR Committee on Editorial and Publication Affairs, 1995) Nyadawa, Maurice O.; Kobatake, Shigeki; Ezaki, Kazihiro
    Presented in this paper is a study clarifying any distinctions or similarities in trends of extreme value statistics of rainfall and discharges recorded at stations sampled all over a basin traversing three distinct climatic zones in Kenya. It is found that in Athi basin, difference in seasonal rainfall pattern affect general characteristics of intense rainfall more significantly than spatial variation of mean annual rainfall. Survey of flood potential of the basin revealed zones which are considered hydrologically homogeneous and heterogeneous cases.
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    Publication
    Probabilistic landslide risk assessment: Case study of Bujumbura
    (EDP Sciences, 2018-12-14) Shirambere, Gervais; Nyadawa, Maurice O.; Masekanya, Jean pierre; Nyomboi, Timothy
    A spatial probabilistic landslide risk assessment and mapping model has been applied in a data scare region. The probabilistic model is based on a physical model based on Mohr coulomb failure criterion. A Monte Carlo simulation technique is applied to field collected data. The results are integrated and a probability of landslide is obtained at each cell level. The results are compared to a prepared landslide inventory. The overall accuracy of the model is 79.69%.
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    Publication
    Seawater Intrusion Vulnerability Assessment of a Coastal Aquifer: North Coast Of Mombasa, Kenya as a Case Study
    (International Journal of Engineering Research and Application, 2016-08) Idowu, Temitope Ezekiel; Nyadawa, Maurice O.; K’orowe, Maurice
    Groundwater pollution in the north coast of Mombasa is not only from surface sources but also from the intrusion of seawater via the Indian Ocean and creeks. This study assessed the vulnerability of the coastal aquifer to seawater intrusion using GALDIT index overlay method with the aid of GIS. Thematic maps of six major factors affecting seawater intrusion were prepared, and given appropriate weightages and ratings. These maps were overlaid, spatially analyzed to produce vulnerability maps and described based on low, moderate or high vulnerabilities. The results revealed a significant increase in percentage land cover for low vulnerability areas and a slight increase for high vulnerability regions between the pre-rains and the peak of raining season. The outcomes of this study provide useful insights on effective groundwater management for the study area.
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    Sedimentation Effect on the Storage Capacity in Lake Nakuru, Kenya
    (JOURNAL OF SUSTAINABLE RESEARCH IN ENGINEERING, 2020-09-16) Iradukunda, Parfait; Sang, Joseph K.; Nyadawa, Maurice O.; Maina, Caroline W.
    The sediment accumulation in rivers and the sediment deposition in the reservoirs is currently influencing a remarkableimpact on the land and water resources in Kenya. Inappropriate land use and wastes disposal in the watershed are anthropogenicactivities resulting in the contamination of the water body in Lake Nakuru. This research study focusses in the lake sedimentationassessment and examination of sediments impacts on the storage loss in Lake Nakuru. This was achieved by establishing theengineering concepts using Bathymetric Surveying System (BSS) comprises navigation twin boats system (Dual-Jon-Boats), built-in Global Positioning System (GPS) for collecting spatial data, acoustic multi-frequency system with higher frequency of 200 kHzfor determination of surface of the sediments and the lower frequency of 12 kHz for determination of deposited sediments layer topre-impoundment levels of the Lake. The software like Depthpic 5.0.2, Surfer 15.5 and ArcGIS 10.3 were used for mapping,gridding and morphometric analysis. The study results show that the lake depth increasing from the shoreline to the middle patchof the lake with the maximal depth of 6.2 meters and the water storage volume of 264,699,344.54 m 3 . The sediment depositionwith the layer thickness varies from 0 m up to 0.7 m (maximum) and the total sediment storage capacity of 24,191,688.67 m 3 , thisimplies that the sediment storage in the lake occupies 8.37 % of its actual storage capacity. The water and sediment storage statuscater to accurate information to the water resources managers in making decisions to the resources’ management in or around thelake.
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    Publication
    The Effect of Climate Change on Loss of Lake Volume: Case of Sedimentation in Central Rift Valley Basin, Ethiopia
    (MDPI, 2018-12-11) Takele, Gadissa; Nyadawa, Maurice O.; Fiseha, Behulu; Mutua, Benedict
    Evaluating the impact of climate change on sediment yield has become one of the major topics in climate research. The purpose of this study was to investigate sediment yield contribution to lake volume change under changing climatic conditions in the Central Rift Valley Basin. The ensemble mean of five regional climate models (RCMs) in the coordinated regional climate downscaling experiment (CORDEX)-Africa was considered for the purpose of this study. The climate variables (precipitation, minimum and maximum temperatures) in RCMs were bias corrected against observed data (1985–2016) using linear scaling (LS), power transformation (PT), variance of scaling (VS), and quantile mapping (QM). Two emission scenarios, the Representative Concentration Pathways, RCP4.5 and RCP8.5, were considered for the future scenario period (2041–2070). Better results were obtained when the ensemble values of the bias correction methods were used. Hence, the projected values of climate variables after bias correction were used in the Soil and Water Assessment Tool (SWAT) hydrological model to estimate the sediment yield contribution to lake volume change due to climate change. The results show that the average projected precipitation will decrease by 7.97% and 2.55% under RCP4.5 and RCP8.5, respectively. On average, the maximum temperature will increase by 1.73 °C and 2.36 °C under RCP4.5 and RCP8.5, respectively, while the minimum temperature will increase by 2.16 °C and 3.07 °C under RCP4.5 and RCP8.5, respectively. The average annual sediment yield contributions to Lake Ziway were 431.05 ton/km2 and 322.82 ton/km2 for the Meki and Ketar rivers, respectively, in the historical period (1985–2010). The study also reveals that the annual sediment yield that was estimated for the Meki River was 323 ton/km2 and 382 ton/km2 under RCP4.5 and under RCP8.5, respectively. The sediment estimations for the Ketar River were 157 ton/km2 and 211 ton/km2 under RCP4.5 under RCP8.5, respectively. This will decrease the rate of volume change in Lake Ziway by 38% under RCP4.5 and by 23% under RCP8.5. The results show that the life expectancy of the lake is likely to increase under climate change scenarios. This will help water resources managers make informed decisions regarding the planning, management, and mitigation of the river basins.
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    Publication
    Use of downscaled tropical rainfall measuring mission data for meteorological drought monitoring: case study of Narumoru catchment
    (International Journal of Advances in Engineering & Technology, 2014) Mutuga, K. J.; Nyadawa, Maurice O.; Home, P. G.
    Remotely sensed satellite rainfall data has gained popularity in the recent past, been especially attractive to ungauged catchments or poorly gauged catchments. Tropical Rainfall Measuring Mission (TRMM) data is considered to be most accurate of the satellite derived rainfall data and with the best spatial resolution at 250 x 250 grid. For purposes of hydrological modelling in small catchments, this data is usually downscaled to 1km x 1km grid to bring it closer to point measurement rain gauge data. This study evaluates whether downscaling of TRMM improves its meteorological drought monitoring capacity. TRMM was downscaled from the original 250 x 250 resolution (Approximately 28km x28km) to 1km x 1km resolution based on the relationship between Normalised Difference Vegetation Index (NDVI) and precipitation. Standardized Precipitation Index (SPI) was computed at 3, 6, 9, 12, and 24-month aggregation periods using the downscaled TRMM data (TRMM1km), TRMM at original resolution (TRMM28km) and observed rain gauge data. Analysis of Variance (ANOVA), t-test and data visualization methods were used to determine the similarity of the SPIs from the three datasets. Similarly, correlation analysis was done to determine dependency and modelling capability of the datasets. TRMM1km derived SPI was found to have lower correlation with the (correlation coefficients ranging from 0.34 to 0.42 for the different aggregation periods) rain gauge derived SPI as compared to TRMM28km derived SPI which had correlation coefficients ranging from 0.57 to 0.66. From analysis of variance, there was no significant difference between the SPI computed from TRMM and from that computed from rain gauge data. Additionally, SPI visualization indicated similar drought patterns were identified by both TRMM and rain gauge computed SPIs. Therefore, it was concluded that TRMM data, whether downscaled or at original resolution are useful for meteorological drought monitoring in Narumoro catchment