Soil Erosion Conservation Research Articles

A statistical-based geospatial approach to prioritize the watersheds for soil erosion conservation in the Upper Awash Basin (Upstream Koka), Ethiopia

The current study focuses on the Upper Awash basin's morphometric parameters to understand the watershed's hydrologic characters with respect to soil erosion conservation. A correlation analysis based on a weighted sum approach was adopted to address the objectives of this research. The drainage patterns were extracted from SRTM-DEM (Shuttle Radar Topography Mission-digital elevation model), and ‘Stahler’s method’ was adopted to determine the stream order. The standardized formulas were employed to calculate about 23 different morphometric parameters. The Upper Awash basin (Koka) has been classified into six watersheds (WS-1 to WS-6). There are eleven selected variables, namely bifurcation ratio (Rb), drainage/stream frequency (Fs), drainage density (Dd), texture ratio (T), drainage texture (If), length of overland flow (Lo), form factor (Ff), shape factor (Bs), elongation ratio (Re), compact coefficient (CC) and circularity ratio (Rc) were used for prioritization ranking and categorization. The study has inferred four categories: very high, high, medium, and low, using the quartile statistical method and weighted compound value. Soil erosion is a major concern in watersheds composed of weak igneous rocks such as ignimbrite and holocene sediments such as limestone, conglomerate, sand, silt, and clay. Hence, three watersheds (WS-4, WS-5, and WS-6) with 53 % of the area have been identified as having strong soil erosion potential, representing very high and high categories requiring immediate conservation measures. Soil erosion conservation efforts and water resource management initiatives will benefit greatly from this effort. In addition, this study confirms that environmental studies utilizing a statistical approach based on GIS (geographical information system) are highly beneficial.

Understanding the linkages between land-use transitions and soil erosion/sediment deposition: A case study of the transboundary Sio-Malaba-Malakisi watershed in Kenya and Uganda

Soil erosion consequent of unsustainable land-use practices represents one of the world's most pressing environmental problems affecting many watersheds. An assessment of sediment sources and delivery paths is essential for the development of site-specific soil management strategies for curbing environmental degradation. The present study employed a physically-based lumped approach to estimate soil erosion and sediment deposition patterns across the transboundary Sio-Malaba-Malakisi (SMM) watershed. The Unit Stream Power-based Erosion Deposition (USPED) model was adopted for the study, and integrated with physically-based parameters derived in a Geographical Information System (GIS). A land-use map for 2017 was used for simulating the reference soil erosion and deposition status of the basin. Furthermore, the impacts of two land-use scenarios representing options for cropland expansion (Scenario-I), and land reclamation (Scenario-II), were evaluated for the period 2047, corresponding to a thirty-year period used in assessing catchment management planning for SMM. The annual soil erosion ranged between 0 and 460 t. ha−1yr−1, with a mean erosion rate of 160 t.ha−1yr−1 for the baseline condition. Deposition zones were mainly concentrated along stream banks and floodplain in low-lying sub-catchments. The mean soil erosion rate increased by 61 % and 16 % for scenarios I and II respectively. Overall, the modelled erosion/deposition values were correlated with available sediment data for the basin, realizing a coefficient determination (R2) value of 0.74. These results could serve as a benchmark against which future trends in land-use changes can be compared in the region and hence support the development of regional soil erosion conservation strategies.

Gully internal erosion triggered by a prolonged heavy rainfall event in the tableland region of China's Loess Plateau

Gully erosion is a severe form of soil erosion, but gully internal erosion processes are poorly understood, especially at the event scale. To investigate gully internal erosion intensity and understand the related gully development mechanism in an agricultural environment with gully head stabilization and vegetation restoration efforts, two successive field investigations were carried out just before and after a prolonged rainfall event in 2021 in the tableland region of China's Loess Plateau. Thirteen gullies were investigated and all experienced gully internal erosion, while most gully boundaries were stable during the heavy rainfall event based on the comparison of the UAV digital orthograph maps (DOMs acquired with Unmanned Aerial Vehicle) before and after the rainfall event. The proportion of gully internal erosion area to gully internal area of the 13 investigated gullies ranged from 3 to 55%, with average areal erosion proportion of the gully sidewall and gully bed of 21% and 36%, respectively. The erosion area of subdrainage units (SDUs) on the gully sidewall was positively correlated to the SDU area, average SDU slope gradient and vegetation type, while the erosion area on the gully bed was positively correlated to the gully area, gully depth and gully bed slope gradient. Gully internal erosion was not significantly correlated with gully drainage area because the connectivity between the upslope and gully areas was interrupted and the effective drainage area of the gully was obviously reduced by soil erosion conservation measures, including terraces on the upslope drainage area, shrub belts, and water barriers. Thus, gully internal erosion is still active under the heavy rainfall storm against the background of the ‘Grain for Green’ and ‘Gully Stabilization and Tableland Protection’ programs, and integrated measures for preventing both gully expansion and gully internal erosion must be further enhanced in the context of climate change.

Gully erosion vulnerability modelling, estimation of soil loss and assessment of gully morphology: a study from cratonic part of eastern India.

A highly visible form of soil erosion is gully, a significant geomorphological feature, resulting from water erosion and causing land degradation and deterioration. In arid and semi-arid environment, gully erosion is conceived as an important source of sediment supply washing out the top fertile soil and exposing lower soil layers. The present study is conducted on the lateritic terrain of Rupai watershed of eastern plateau fringe of India, where water erosion is a serious concern. In order to prepare a gully erosion vulnerability mapping, the analytical hierarchy process (AHP) model coupled with geospatial technology is adopted taking into account thirteen bio-physical factors. It is revealed that around 49% area of the watershed belongs to high to very high gully erosion vulnerability zone (GEVZ) followed by moderate risk zone of 31.64%. This model is validated performing an accuracy assessment, which is calculated to be 90.91%, and the value of Kappa co-efficient is 0.86. It is imperative to estimate the average annual soil loss alongside of delineating GEVZ; thus, the revised universal soil loss equation (RUSLE) model is used with geospatial technology. It unveils that the average estimated soil loss of the watershed varies from < 15 to 431 t ha-1 y-1. Around 29% of the study area experiences high to very high (57 to > 147 t ha-1 y-1) soil erosion risk, where 68% area endures low level of soil erosion risk (< 15 t ha-1 y-1). The study of gully morphology depicts gully depth ranging from < 1 to 5m (small to medium gully) with V and U shapes. Results obtained from this study may help in planning and management of land use and soil erosion conservation.

Prioritization of Sub-watersheds of Kosi River Basin Using Morphometric Analysis and Geospatial Tools

This study aimed to use remote sensing (RS) and geographic information system (GIS) geospatial tools for morphometric investigation of a mid-Himalayan Kosi river basin in Uttarakhand, India. The sub- watersheds (SWs) were identified and prioritized into high, medium, and low level of priority based on the compound factor analysis for conservation of natural resources in the watershed, leading to sustainable watershed management. Total of 10 morphological parameters related to drainage network, basin geometry, and drainage texture were used for compound factor analysis. The drainage network of the river basin was dendritic in nature and exhibited homogeneity in texture and lack of structural control that helped in analysing terrain parameters as drainage density, infiltration capacity, runoff, bedrock nature, which control underground water movement. The stream-order estimated using the digital elevation model (DEM) having 12.5 m × 12.5 m spatial resolution ranged from first to seventh order streams. During prioritization of sub-watersheds using compound factor values, higher priority was assigned to sub- watersheds which yielded lowest compound factor and vice-versa. Sub-watersheds SW5 to SW7 covering an area of 396.18 km2 were noted to have highest priorities for soil erosion conservation measures; SW2, SW3 and SW8 had medium priorities; and SW1, SW9, and SW4 were assessed with lowest priorities. It is anticipated that the prioritization of sub-watersheds would be useful to planners, decision makers, and relevant stakeholders for implementation of soil and water conservation interventions for sustainable natural resources management within watershed.

Soil conservation efficiency assessment based on land use scenarios in the Nile River Basin

Soil conservation is one of the most important ecosystem services, as it has a positive impact on soil fertility and land productivity. Although soil conservation includes multiple facets, existing research on soil conservation has rarely considered the combination of soil erosion and sediment within its analysis. In this context, this paper uses the Revised Universal Soil Loss Equation (RUSLE) and the Sediment Delivery Ratio (SDR) module of Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) to develop a Soil Conservation Efficiency Index that accounts for both soil erosion conservation efficiency and river sediment transport conservation efficiency. A natural growth and reforestation scenario of land use change was applied and modelled with the Nile River Basin from 2010 to 2100. Three main results were obtained: (1) From 2000 to 2010, grassland increased by 4.34%, and the forest decreased by 4.91%. (2) From 2000 to 2100, soil conservation presents a declining tendency in the two scenarios, and the soil conservation amounts based on soil erosion and sediment were 1550.48 ± 177.12 and 100.93 ± 6.24 (t ha−1 y−1) in a natural growth scenario, respectively, and 1576.78 ± 63.21 and 104.41 ± 0.30 (t ha−1 y−1) in a reforestation scenario, respectively. (3) It was found that the reforestation scenario was the most effective. With soil erosion conservation efficiency being most effective in the first fifty years, and the river sediment transport conservation efficiency being more effective from 2010 to 2100. Overall, when reducing the conversion rate of forest land by 0.5 times and increasing the rate of conversion to forest by 0.5 times, the effect of land use changes to river sediment transport conservation efficiency has a longer-term effect than changes to soil erosion conservation efficiency.

Assessment of soil erosion, sediment yield and basin specific controlling factors using RUSLE-SDR and PLSR approach in Konar river basin, India

The study comprehensively assessed the effects of river basin parameters (basin morphology, drainage network, topography, climate, land use land cover (LULC) composition & pattern, and soil properties) on soil erosion (SE) and specific sediment yield (SSY) in the tropical river basin of Konar, India. The revised universal soil loss equation (RUSLE) along with the sediment delivery ratio (SDR) model has been used to quantify the SE and SSY. As the basin parameters are highly codependent with each other, multivariate partial least square regression (PLSR) with variable importance projection (VIP) statistics has been applied to 32 basin parameters to elucidate the linkage with SE and SSY. Multi-spectral LANDSAT-8 image, topographical sheets (1:50,000), gridded (0.25° × 0.25°) daily rainfall data series, laboratory estimates of soil parameters along with other ancillary data have been employed in this regard. Results revealed that wastelands encouraged moderate to very high (5–40.0 t ha−1 yr−1) annual rate of SE compare to other LULC classes. The PLSR studies revealed that the mean slope gradient (S), basin relief (HD), sediment delivery ratio (SDR), patch density (PD), edge density (ED), hypsometric integral (HI), topographic wetness index (TWI) were very strongly influential (b = 0.1–0.16) in SE. Likewise, SDR, mean annual precipitation (P), rainfall-runoff erosivity (R factor) PD, S, and HD were highly (b=0.12–0.22) important variables (VIP = 1.2–2.3) for SSY. Generated spatial information may help in understanding the SE and SSY dynamics in the basin and the knowledge can be used for soil erosion conservation measures in and around the river basins in India.

Using hybrid weighting‐clustering approach for regional frequency analysis of maximum 24‐hr rainfall based on climatic, geographical, and statistical attributes

Estimation of extreme rainfall amounts has great importance, especially in some fields such as the design of water structures, water resources engineering, extreme flood management, and soil erosion conservation. One of the problems, which hydrologists faced, is an acceptable estimation of extreme events in areas with insufficient data. In this case, separation of the study area into homogenous regions and performing regional frequency analysis (RFA) result in greater precision and fewer errors in frequency analysis models, enabling estimation of quantiles for each return period in the region of interest. In this study, the maximum 24‐hr rainfall data related to Lake Urmia Basin (LUB) for 63 selected stations during the period of 1979–2008 are used. Moreover, determining an appropriate weight for each group of attributes is attempted according to the degree of importance and contribution share of each climatic, geographical, and statistical attribute. Then, for regionalization using a clustering approach, the attributes are defined in seven different groups. Subsequently, the performance of different groups associated with weighted attributes of maximum 24‐hr rainfall is evaluated for RFA in the study area. The results showed that the combination of climatic, geographical, and statistical attributes present better results and more reliable estimates of extreme values. The results indicated better performance of weighted models to the attributes compared to non‐weighted frequency analysis models in the estimation of maximum 24‐hr rainfall. The results also showed that by evaluating three to four groups and applying average weights of 0.3–0.85 for the attributes through the use of hybrid weighting‐clustering approach, more accurate estimates of extreme values for different return periods can be obtained.

Fuzzy Ideal Points Method In Project Construction Sequence of the Downstream of Yellow River

Based on the project construction and investment feature of the Downstream of Yellow River, the structures were divided into flood control dike, water diversion, irrigation and water saving, soil erosion conservation and ecological projects, river mouth management and development and water resources information. Using fuzzy and decision making analysis theory and project planning investigation data, the different project weights were calculated and fuzzy ideal point model was set up. According to administrative region, the total area of the downstream of the Yellow River was divided as 14 sub-regions. Using the model to solve the project construction sequence, the sequence scheme of the water project construction was achieved. The results have an important significance for the different water projects construction of the downstream of the Yellow River.

Soil erosion and sediment yield and their relationships with vegetation cover in upper stream of the Yellow River

Soil erosion is a significant concern when considering regional environmental protection, especially in the Yellow River Basin in China. This study evaluated the temporal-spatial interaction of land cover status with soil erosion characteristics in the Longliu Catchment of China, using the Soil and Water Assessment Tool (SWAT) model. SWAT is a physical hydrological model which uses the RUSLE equation as a sediment algorithm. Considering the spatial and temporal scale of the relationship between soil erosion and sediment yield, simulations were undertaken at monthly and annual temporal scales and basin and sub-basin spatial scales. The corresponding temporal and spatial Normalized Difference Vegetation Index (NDVI) information was summarized from MODIS data, which can integrate regional land cover and climatic features. The SWAT simulation revealed that the annual soil erosion and sediment yield showed similar spatial distribution patterns, but the monthly variation fluctuated significantly. The monthly basin soil erosion varied from almost no erosion load to 3.92 t/ha and the maximum monthly sediment yield was 47,540 tones. The inter-annual simulation focused on the spatial difference and relationship with the corresponding vegetation NDVI value for every sub-basin. It is concluded that, for this continental monsoon climate basin, the higher NDVI vegetation zones prevented sediment transport, but at the same time they also contributed considerable soil erosion. The monthly basin soil erosion and sediment yield both correlated with NDVI, and the determination coefficients of their exponential correlation model were 0.446 and 0.426, respectively. The relationships between soil erosion and sediment yield with vegetation NDVI indicated that the vegetation status has a significant impact on sediment formation and transport. The findings can be used to develop soil erosion conservation programs for the study area.

Soil erosion dynamics response to landscape pattern

Simulating soil erosion variation with a temporal land use database reveals long-term fluctuations in landscape patterns, as well as priority needs for soil erosion conservation. The application of a multi-year land use database in support of a Soil Water Assessment Tool (SWAT) led to an accurate assessment, from 1977 to 2006, of erosion in the upper watershed of the Yellow River. At same time, the impacts of land use and landscape service features on soil erosion load were assessed. A series of supervised land use classifications of Landsat images characterized variations in land use and landscape patterns over three decades. The SWAT database was constructed with soil properties, climate and elevation data. Using water flow and sand density data as parameters, regional soil erosion load was simulated. A numerical statistical model was used to relate soil erosion to land use and landscape. The results indicated that decadal decrease of grassland areas did not pose a significant threat to soil erosion, while the continual increase of bare land, water area and farmland increased soil erosion. Regional landscape variation also had a strong relationship with erosion. Patch level landscape analyses demonstrated that larger water area led to more soil erosion. The patch correlation indicated that contagious grassland patches reduced soil erosion yield. The increased grassland patches led to more patch edges, in turn increasing the sediment transportation from the patch edges. The findings increase understanding of the temporal variation in soil erosion processes, which is the basis for preventing local pollution.

Mapping of soil erosion using remotely sensed data in Zombodze South, Swaziland

Zombodze South is situated in the southern part of Swaziland. It has visible signs of soil erosion. However like many parts of the country, soil erosion has not been mapped. The area lacks soil conservation measures. The objective of the study was to map the spatial distribution of soil erosion, and to determine the perception of community members on soil erosion problems. IDRISI for Windows was used to produce 20 clusters from Landsat ETM data for January 1999. The clusters were allocated to five land cover classes based on a combination of use of “scatterplots” and NDVI values. Gullies were identified on digital aerial photos of the area, and digitized. Other land features such as settlements, roads and rivers were also digitized. A structured questionnaire was administered to 40 homesteads that were randomly selected from the 234 homesteads in the community to collect information on perception of communities on soil erosion, as well as their involvement in controlling soil erosion. About 4% of the area was eroded, with another 38% having very sparse vegetation cover. Gully erosion was prevalent in the southern part of the area. The limited soil erosion conservation measures in the area were undertaken by local school children as part of their school projects. The control measures suggested by members of the community included planting trees and grasses along the gullies, fencing of gullies and construction of check dams.