Abstract:
This study was undertaken in Kitui South in Kitui County in the south eastern parts of Kenya. The
main objective of the study was to develop a spatial model that can be used for selection of suitable
sites for sand dam in Kitui South. Data analysis was done using three approaches. The first
approach involved the use of the Remote Sensing (RS) technique where data was preprocessed
and analyzed using Erdas Imagine software and Geographical Information Systems (GIS) for
spatial modelling. Sand samples were collected from seasonal rivers which included Mwila,
Kakya, Wiitu, Nguni, Ngunyumu, Muvuko, Kanzilu, Masaa, Katiliku, Ngulungu, Nzeeu, Koma
and Katitika. The results from the spatial model which integrated all factors shows that 16% of the
studied sites were fairly suitable for construction of sand dams while 79% were classified as
suitable and 5% are categorized as very suitable. Several sites in the central and the entire eastern
parts of Mutha Ward were found not suitable for sand dam construction due to poor conditions
such as the lack of suitable sand particles, lack of bedrock exposure on the riverbeds, flat terrain,
very shallow stream banks, and weak soils on the riverbanks. Suitable sites for sand dams were
found on the western and central areas of Kitui South where production and high accumulation of
coarse sands while few excellent sites were observed in Ikanga ward and near Mutomo hills.
Optimum accumulation of sands along the seasonal streams was identified at a slope ranging
between 1.5 and 6%. Accumulation of different grades of sand especially the medium sands (r=
0.76) and coarse sands (r=0.75) were found to be strongly influenced by the changes in elevation
along the stream. Out of 80 investigated sites, 59% of them were dominated with uniform sands
(Cu<3), 30% were intermediate sands and only 11% were well-graded sands (Cu>5). The study
also found that86% of the sites along the seasonal streams were dominated with medium sands
while 10% were dominated with fine sands and the rest (4%) dominated by coarse and gravelly
sands. From the results this study concludes that 59% of the 80 sites that were investigated in this
study have a high potential for providing suitable sites for sand dams in Kitui South Sub-County.
