The Use of Satellite Images to Monitor the Effect of Sand Dams on Stream Bank Land Cover ChaNges In Kitui District

Abstract

A study was carried out to investigate the effect of sand dam construction on land cover changes along the stream bank during the dry season using satellite images. Two water catchments namely Kiindu and Mbusyani in Kitui district that have similarities in topographical features were chosen for the study. Land cover change detection analysis was done by use of Landsat ETM+ 2001 and Landsat TM 1986 satellite images for Kiindu and Mbusyani catchment for the period 1995- 2001 (after sand dam construction) and 1986 (before sand construction) respectively. Based on the reference data collected from the field two land cover types were of significance importance for the research study i.e. vegetation and bare land. The classification involved identifying areas of vegetation existence and nonexistence during the dry season along the stream banks. Following the classification a change detection analysis was carried out between 2001 and 1986 whose results indicated an increase in vegetation as result of sand dam construction. Kiindu catchment vegetation increased by 52% whilst Mbusyani increased by 43% in 2001 i.e. The relative change in area (ha) from bare land to vegetation was 1356.5 ha and 1218.8 ha compared to vegetation in 1986 which was 229.7 ha and 264.3 ha respectively. The overall accuracies of the classification maps for the two catchments were; Kiindu 90% in 2001 and 87% in 1986 with Kappa Statistics of 0.74 in 2001 and 0.67 in1986. Mbusyani on the other hand had 89% in 2001 and 87% in 1986 with Kappa Statistics of 0.78 in 2001 and 0.66 in 1986. The results from the analysis therefore indicated that sand dam did have a significant influence on land cover changes along stream bank channels during the dry period.