A Study of the Dynamics of Soil Erosion Using Rusle2 Modelling and Geospatial Tool in Edda-Afikpo Mesas, South Eastern Nigeria

Abstract

The Revised Universal Soil Loss Equation (RUSLE) was used to study the soil erosion processes in Edda-Afikpo mesas, Lower Cross River watersheds,Nigeria. The mesas occupy an area estimated at 60km2 on a surface relief of about 284m. DEM data, satellite images and basemap of the area were used. Remotely sensed data were ground-truthed through extensive field works. The results show that the process is facilitated by the Trifecta of hill slope hydrology, geology and land use practices. Steep hill Slope of values 78 % at the major hot spots, very fragile, dry and non-plastic sandy soils all aid sediment detachment. Analysis of the index properties which include Liquid Limit(LL) of 25-30, moisture content(w%) of 5.9-7.4, permeability of 1.541x10-3 – 1.636x10-3 cm/s and shear strength of 36-42 KN/m2 predispose the sediments to detachment and erosion. Based on the analysis, the amount of soil loss in the project area is about 1373.79 ton per year. Soil erosivity factor is high at the mesas(5023.83 MJ mm ha−1 h−1 yr−1 - 5069.51 MJ mm ha−1 h−1 yr−1) The sandy layer attain thickness of 50m-60m in places and with high pore pressure development, slope failure are triggered during intense storm events. In terms of vulnerability level in erosion risk, high to very high constitute 4.1% of the watershed which translate to 5.05km2 of the 59km2. The various processes occur simultaneously and are exacerbated by human factors through seasonal bush burning and development along drainage lines. The study reveals that 18.8% of the available land for development is at high to very high risk of erosion. The soil loss model has been validated and the hotspots from the map coincide with the gully sites. The results of this research can therefore be used for conservation and adaptation purposes.

Soil loss estimation and prioritization using geographic information systems and the RUSLE model: a case study of the Anger River sub-basin, Western Ethiopia

“…Thus, a knowledge and information gap exists on the status and severity of soil loss in the Anger River Sub-basin. To fill this gap, we adopted the RUSLE model and a geographic information system (GIS) as previously used (Haile & Fetene 2011;Thomas et al 2018;Zerihun et al 2018;Amah et al 2020;Mohammed et al 2020;Kebede et al 2021;Moisa et al 2021) to estimate the amount of soil loss in the Anger River Sub-basin. A majority of the previous studies, including the recent study of Moisa et al (2021), emphasized on the impact of LULC change on soil erosion with prioritization of sub-watersheds for conservation planning.…”

Prioritizing management options using a risk assessment for soil erosion based on GIS, remote sensing, and RUSLE. A case study of Midhagdu Watershed, Eastern Ethiopia.

“…A color-printed soil erosion risk map was taken to the eld to investigate the real-world phenomenon in the study site based on the graduated color assigned to the level of soil erosion risk area identi ed on the map. The validity of the soil erosion risk map was judged based on recorded erosion features at XY coordinates in the eld and overlaid on top of the erosion risk map and calculated its accuracy [49,50] by dividing the number of points laid on high, very high and extremely high regions of soil erosion map to the total points collected in the eld and multiplied by hundred. Consequently, based on the generated map versus real-world phenomenon comparison for the model validation, 13 out of the 25 erosion sites fell within the extremely high-risk level of the RUSLE result, while 6 and 4of the erosion sites fell within the very high and high soil erosion risk areas respectively, out of 25 ground-truth erosion site 2 sites were fell in moderate erosion risk area in Midhagdu watershed soil map which makes the soil erosion prediction map 92 percent accurate with the real-world phenomenon.…”

Soil Loss Assessment Using the Revised Universal Soil Loss Equation (RUSLE) Model

“…Many researchers worldwide have adopted this methodology to carry out soil erosion studies at different spatial scales. For instance, the following researchers studied soil loss in catchment areas by applying the RUSLE model, GIS, and remote sensing [18,33,42,53,54,70,72,[77][78][79][80][81][82][83][84]. e studies revealed that, apart from estimating soil erosion, the methodology was found to be satisfactory in identifying areas that had higher soil erosion risks.…”

“…e slope gradient's effect on soil erosion is much more compared to that brought about by slope length [14,106]. is is an indication that soil erosion is much more pronounced especially in highly sloping areas [84,86]. Research has shown that soil erosion is disastrous in slopes ranging between 10 and 25% [14].…”