Deforestation Effects on Soil Erosion in the Lake Kivu Basin, D.R. Congo-Rwanda

Abstract

Deforestation and natural grassland conversion to agricultural land use constitute a major threat to soil and water conservation. This study aimed at assessing the status of land cover and land use (LCLU) in the Lake Kivu basin, and its related impacts in terms of soil erosion by water using the Universal Soil Erosion Equation (USLE) model. The results indicated that the Lake Kivu basin is exposed to soil erosion risk with a mean annual rate of 30 t·ha −1 , and only 33% of the total non-water area is associated with a tolerable soil loss (≤10 t·ha −1 ·year −1 ). Due to both natural factors (abundant tropical precipitation and steep slopes) and anthropogenic activities without prior appropriate conservation practices, all land-use types-namely settlement, cropland, forestland, and grassland-are exposed to a severe mean erosion rate of 41 t·ha −1 ·year −1 , 31 t·ha −1 ·year −1 , 28 t·ha −1 ·year −1 , and 20 t·ha −1 ·year −1 , respectively. The cropland that occupied 74% of the non-water area in 2015 was the major contributor (75%) to the total annual soil loss in the Lake Kivu basin. This study showed that conservation practices in the cropland cells would result in a mean erosion rate of 7 t·ha −1 ·year −1 , 18 t·ha −1 ·year −1 , and 35 t·ha −1 ·year −1 for terracing, strip-cropping, and contouring, respectively. The adoption of terracing would be the best conservation practice, among others, that could reduce soil erosion in cropland areas up to about 23%. The erosion risk minimization in forests and grasslands implies an increase in overstorey canopy and understorey vegetation, and control of human activities such as fires, mining, soil compaction from domestic animals grazing, and so on. Soil erosion control in settled areas suggests, among other things, the revegetation of construction sites, establishment of outlet channels, rainfall water harvesting systems, and pervious paving block with grass.

Soil Erosion Risk Assessment in Uganda

“…Soil erosion, combined with other impacts from forest disturbance, such as soil compaction, can reduce forest sustainability and soil productivity [66]. Soil erosion that was considered a severe problem associated with unsustainable farming methods [66,67] could be controlled by promoting anti-erosion measures such as terracing, strip-cropping, contouring, the planting of cover crops, keeping plant residues at the soil surface, the maintenance of stone walls, and the increased use of grass margins [52,60,67]. Under the state of 2014 land management in Uganda with a P factor value of 0.75 reported by the LADA project [3], the total cropland (86,341.86 Km 2 ) was exposed to a moderate mean estimated soil erosion rate of 1.5 t·ha −1 ·y −1 in 2014; 30.4% of the croplands comprised an unsustainable mean soil loss >1 t·ha −1 ·y −1 , while 2.6% of the croplands that had high soil loss rates >10 t·ha −1 ·y −1 were located on very steep slopes ranging from 28% to 38% with an abundant rainfall intensity ranging from 1143 to 1147 mm·y −1 (Figure 8a).…”

Determining RUSLE P‐ and C‐factors for stone bunds and trenches in rangeland and cropland, North Ethiopia

“…As a consequence, researchers are often forced to guess values for these factors without knowing to what extent these values are representative for the implemented measures or the environment. This forms a major bottleneck for soil erosion prediction and understanding impacts of natural resource management in Ethiopia and many other developing countries (Karamage et al, ; Mati et al, ; Nigussie et al, ; Nyssen et al, ; Sonneveld, Keyzer, & Albersen, ). A further challenge is that, although several studies show that commonly applied SWC measures such as stone bunds and trenches are highly effective (Desta et al, ; Nyssen et al, , ; Taye et al, ), their effectiveness can also strongly decline over time, due to a decline in static storage capacity (SSC; Guzman et al, ; Taye et al, ).…”

“…As a consequence, researchers are often forced to guess values for these factors without knowing to what extent these values are representative for the implemented measures or the environment. This forms a major bottleneck for soil erosion prediction and understanding impacts of natural resource management in Ethiopia and many other developing countries (Karamage et al, 2016;Mati et al, 2000;Nigussie et al, 2014;Nyssen et al, 2008;Sonneveld, Keyzer, & Albersen, 2001).…”

Modeling Rainfall-Runoff Response to Land Use and Land Cover Change in Rwanda (1990–2016)

“…Nowadays, deforestation and natural grasslands conversion for urban expansion and agricultural intensification due to rapid population growth have become a critical environmental issue [1][2][3]. Urbanization expansion increases impervious covers that reduce infiltration capacity, leading to downstream flooding, stream bank erosion, increased turbidity (muddiness created by stirred up use the data currently available in GIS format.…”