Erosion Potential Index Research Articles

Evaluating the continued significance of dam-induced vigorous downstream channel erosion in the context of projected climate change: a case study from Peninsular India

ABSTRACT Although erosion has naturally been driven by rainfall patterns, human activities have increasingly influenced erosion rates in recent times. However, as climate change alters precipitation, future erosion control may once again depend primarily on climate. The primary goal of this investigation was to ascertain whether the issue of escalated erosion, typically linked to downstream dam effects, could diminish in significance due to projected climatic shifts later in this century. An erosion potential index (Ep), formulated as the ratio of the mass of sediment influx from upstream to the frequency of the sediment-carrying flow events, was computed on a tributary of the Godavari River, located downstream of a dam. Using the Soil & Water Assessment Tool (SWAT), virtual experiments were conducted to distinguish the impacts of the dam from projected climate changes on river geomorphology. Two control scenarios were created using the current climate data and simulated regulated and unregulated states of the basin. Employing climate projections and various mitigation scenarios (SSPs) for the 2060s and 2090s, this study estimated Ep values exclusively under future climatic conditions in an unregulated state of the basin. Results indicate that, in the unregulated state without the existence of the upstream dam, future climate impacts on erosion outweigh the current effects of the dam, underscoring the growing influence of climate on geomorphology. It suggests that existing structural interventions may lose their geomorphic significance in the face of future climate conditions.

Storm frequency, magnitude, and cumulative storm beach impact along the US east coast

Abstract. This study extracted historical water level data from 12 National Oceanographic and Atmospheric Administration tide gauge stations, spanning the period from the early 20th century to 2022 from central Maine to southern Florida, in order to determine if temporal and spatial trends existed in the frequency and magnitude of storms along the US Atlantic Ocean coast. We used the Storm Erosion Potential Index (SEPI) to identify and quantify storms. We then use the timing and magnitude of those storms to determine the cumulative effect of storm clustering and large-magnitude storms on sandy beaches using the cumulative storm impact index (CSII) empirical model. The results from this study showed (1) no appreciable increase in storm frequency at any of the stations (except for sheltered stations susceptible to storm tide augmentation), (2) statistically significant but modest increases in storm magnitudes over time for 8 of the 12 tidal stations, (3) regional differences in storm magnitudes (SEPI) and cumulative storm impacts (CSII) characteristic of more frequent extratropical storms (temporal clustering) in the north and less frequent tropical storms in the south, and (4) a 4- to 10-year recovery period for regional beach recovery.

Modelling, quantification and estimation of the soil water erosion using the Revised Universal Soil Loss Equation with Sediment Delivery Ratio and the analytic hierarchy process models

AbstractThis research used the Revised Universal Soil Loss Equation (RUSLE) with Sediment Delivery Ratio (SDR) model. The analytic hierarchy process (AHP) method, while also incorporating the use of a geographic information system (GIS) and remote sensing (RS) to predict the annual soil loss rate and spatialise the processes of water erosion at the scale of the Loukkos Watershed, Morocco. The RUSLE model and AHP parameters were estimated using RS data, and the erosion vulnerability zones were determined using GIS. We used five parameters, including precipitation erosivity, soil erodibility, slope length and steepness, vegetation cover, and soil erosion control practices in the RUSLE. For the AHP technique, we used seven geo‐environmental factors, including annual average precipitation, drainage density, lineament density, slope, soil texture, land use/land cover and landform maps. The results of RUSLE indicated that the average annual soil loss varied from 0 to 2388.27 . The total estimated annual potential soil loss was approximately 40 790 220.11 , and a sediment yield estimated by RUSLE‐SDR was 8 647 526.66 , equivalent to 6.65 Mm3. This value is very close to the measured value of 6.81 Mm3, for a difference of 0.16 Mm3. Furthermore, the results of the AHP indicate that the soil erosion potential index varies from 0 to 0.205315 . Overall, nearly 13.7% of the area suffered from severe soil erosion exceeding 50 . Approximately 80% of the Loukkos Watershed area experienced only slight erosion, while the remaining 6% incurred moderate erosion. Integrating GIS and RS into the RUSLE model and AHP helped us robustly estimate the extent and degree of erosion risk. Territorial decision‐makers should adopt our results to develop soil conservation strategies, water management plans and other necessary soil and water conservation measures for this region.

Identification of spatially distributed hotspots for soil loss and erosion potential in mining areas of Upper Damodar Basin – India

Limited measurements of soil erosion, sediment transport and deposition due to coal mining activities hamper the planning for soil and water management in large coalfields. Management of erosion in these areas requires the identification of vulnerable zones. In this study, a modified Universal Soil Loss Equation model coupled with Analytic Hierarchy Process has been used to develop an Erosion Potential Index (EPI) to identify probable zones of soil erosion in the Upper Damodar Basin (UDB). The Damodar river valley has been subjected to severe environmental contamination over the years due to large scale mining and industrial activities. The results revealed that north-western and the central part of the UDB lied in the high EPI zone. Revised Universal Soil Loss Equation (RUSLE) model was used to estimate the soil loss for the UDB. The results of the RUSLE model revealed that the soil loss in the study area varied from a minimum of 0 to a maximum of 91.34 t ha−1 yr−1 in some areas. The spatial distribution of soil loss in the UDB was classified into 5 categories (Very Slight, Slight, Moderate, Severe and Extremely Severe). From results it was observed that about 959.9 km2 or 22% of the total study area lied in the severe soil loss zone i.e., soil losses in these areas ranged between 20 and 40 t ha−1 yr−1. Most of these areas were located in the vicinity of coal mining areas. Although, the lack of available data may impair the prediction accuracy of the proposed model at such a large watershed scale. However, the results of the proposed approach indicate usefulness in identifying erosion hotspots in large distributed watersheds with limited data.

Assessment of soil erosion in a monsoon-dominated mountain river basin in India using RUSLE-SDR and AHP

ABSTRACTThe long-term average annual soil loss (A) and sediment yield (SY) in a tropical monsoon-dominated river basin in the southern Western Ghats, India (Muthirapuzha River Basin, MRB; area: 271.75 km2), were predicted by coupling the Revised Universal Soil Loss Equation (RUSLE) and sediment delivery ratio (SDR) models. Moreover, the study also delineated soil erosion risk zones based on the soil erosion potential index (SEPI) using the analytic hierarchy process (AHP) technique. Mean A of the basin is 14.36 t ha−1 year−1, while mean SY is only 3.65 t ha−1 year−1. Although the land use/land cover types with human interference show relatively lower A compared to natural vegetation, their higher SDR values reflect the significance of anthropogenic activities in accelerated soil erosion. The soil erosion risk in the MRB is strongly controlled by slope, land use/land cover and relative relief, compared to geomorphology, drainage density, stream frequency and lineament frequency.

Simultaneous meteorological tsunamis and storm surges at Buenos Aires coast, southeastern South America

Meteorological tsunamis are frequently observed in different tide stations at the southeastern coast of South America. They are associated with the occurrence of atmospheric gravity waves during the passages of cold fronts over the Buenos Aires Province continental shelf. On the other hand, storm surges are also frequent in the region, and they are associated with strong and persistent southerlies, which are also frequent during cold front passages. The impact of meteorological tsunamis in coastal erosion and in the statistics of storm surge trends is discussed in this paper. For this study, fifteen meteorological tsunamis (with maximum wave heights higher than 0.20 m), seven of them simultaneous to the occurrence of storm surge events (with extreme levels higher than |±0.60 m|), are selected from April 2010 to January 2013. The impact of meteorological tsunamis in the storm erosion potential index (SEPI) is evaluated. Not significant differences are obtained between SEPI calculated with and without filtering the meteorological tsunami signal from the storm surge data series. Moreover, several experiments are carried out computing SEPI from synthetic sea level data series, but very low changes (lower than 4 %) are also obtained. It is concluded that the presence of moderate meteorological tsunamis on sea level records would not enhance this index at the Buenos Aires Province coast. On the other hand, taking into account that meteorological tsunamis can reach up the 20–30 % of the storm surge height, it was concluded that the statistics of storm surge trends (and their uncertainties) should be revised for Mar del Plata data series.

Using Rapid Geomorphic Assessments to Assess Streambank Stability in Oklahoma Ozark Streams

High streambank erosion and failure rates on streams in the Ozark ecoregion of Oklahoma may be attributed to land use change and degradation of riparian areas. Numerous benefits may be achieved from streambank stabilization, but methods are needed to determine the most critical reaches for investing limited funds. Rapid geomorphic assessments (RGAs) have been used to aid in prioritizing stream reaches. This research (1) applied an existing RGA, the channel stability index (CSI), on several reaches along the Barren Fork Creek and Spavinaw Creek, and (2) modified the existing RGA to create an ecoregion-specific RGA called the Oklahoma Ozark streambank erosion potential index (OSEPI) for larger-order streams in the area. Aerial photography (2003 to 2008) was used to document recent lateral bank retreat for evaluating the RGA scores. Whereas the CSI provided a relatively simple, inexpensive way to identify reaches that should be further evaluated for stability, it failed to disaggregate unstable stream reaches. Limitations included not considering the streambanks cohesion and the difficulty in assessing some metrics. The OSEPI, which included parameters to account for the streambanks cohesion and stream curvature, had higher correlation (R2 = 0.29 for all reaches; R2 = 0.45 for reaches with similar soils) with recent streambank erosion. These results indicate promise for its use in prioritizing reaches for future stabilization projects in the Ozark region of Oklahoma. Additional research is needed to further test the generic and ecoregion-specific RGAs and to determine the conditions that necessitate ecoregion-specific indices.

Model application to assess effects of urbanisation and distributed flow controls on erosion potential and baseflow hydraulic habitat

The catchment model SWMM was modified to include on-site flow-control devices, and then linked with models of hydraulic habitat suitability and erosive potential for specific reaches in a study catchment. Urbanisation decreased the modelled baseflow by up to 33% and reduced the area of suitable hydraulic habitat by 0.5–13.3%, depending on the reach and species. Hypothetical infiltration devices increased the baseflow to pre-development levels, with an associated increase in habitat, but other measures were not effective. Urbanisation increased the erosion potential index by a factor of 1.58–9.32, depending on the reach. Erosion-control ponds decreased the erosion potential to pre-development level in some reaches. Detention tanks reduced the erosion potential significantly, but not to pre-development levels. The poor predictive ability of the models for baseflow compromised the utility of the hydraulic habitat assessment. Predictions of the effects of urbanisation on baseflow habitat should therefore be treated cautiously.

Ephemeral gully erosion from agricultural regions in the Pacific Northwest, USA

Ephemeral gully erosion from agricultural regions in the Pacific Northwest, USA Soil erosion continues to be problematic financially and environmentally with the USEPA ranking sediment as one of the top ten pollutants of concern in the USA. One aspect of erosion often overlooked is the role of ephemeral gullies in terms of quantity of sediment produced and amount exported to nearby waterways. Current physically-based and empirical models are inadequate for predicting this type of erosion particularly at the watershed scale. A new methodology for predicting the quantity and location of sediment delivery was developed and tested via a case study. Aerial ephemeral gully erosion rates varied from 33.6 mton/km2 (0.15 U.S. tons/acre) in the Big Bear Creek basin to 88.4 mton/km2 (0.39 U.S. tons/acre) in the Middle Potlatch Creek basin representing 2.3 to 7.7% of the total surface sediment load. This information was used to develop a predictive Erosion Potential Index (EPI) that uses LANDSAT aerial imagery combined with readily available soils information and a digital elevation model to identify the most probably locations of ephemeral gully development. High resolution aerial imagery was used to quantify actual ephemeral gully locations which were then compared to the EPI predicted locations to verify the procedure. High resolution aerial imagery was also used to quantify the amounts of soil erosion from ephemeral gullies in basins of the Potlatch River system.

Storm surges and coastal impacts at Mar del Plata, Argentina

Positive storm surges (PSS) lasting for several days can raise the water level producing significant differences between the observed level and the astronomical tide. These storm events can be more severe if they coincide with a high tide or if they bracket several tidal cycles, particularly in the case of the highest astronomical tide. Besides, the abnormal sea-level elevation near the coast can cause the highest waves generated to attack the upper beach. This combination of factors can produce severe erosion, threatening sectors located along the coastline. These effects would be more serious if the storm surge height and duration increase as a result of a climatic change. The Mar del Plata (Argentina) coastline and adjacent areas are exposed to such effects. A statistical characterization of PSS based on their intensity, duration and frequency, including a surge event classification, was performed utilizing tide-gauge records over the period 1956–2005. A storm erosion potential index (SEPI) was calculated from observed levels based on hourly water level measurements. The index was related to beach profile responses to storm events. Also, a return period for extreme SEPI values was calculated. Results show an increase in the average number of positive storm surge events per decade. Considering all the events, the last decade (1996–2005) exhibits an average 7% increase compared to each one of the previous decades. A similar behavior was found for the decadal average of the heights of maximum annual positive storm surges. In this case the average height of the last two decades exceeds that of the previous decades by approximately 8 cm. The decadal average of maximum annual duration of these meteorological events shows an increase of 2 h in the last three decades. A possible explanation of the changes in frequency, height and duration of positive storm surges at Mar del Plata would seem to lie in the relative mean sea-level rise.

Aerial Assessment of Ephemeral Gully Erosion from Agricultural Regions in the Pacific Northwest

Soil erosion from agricultural areas continues to be problematic in terms of both financial and environmental measures. Ephemeral gullies contribute to the soil loss both by the volume of sediment eroded from the gullies and because they act as delivery channels for surface erosion. High resolution aerial imagery was used to quantify the amounts and locations of ephemeral gullies in the subbasins of the Potlatch River system. Areal ephemeral gully erosion rates varied from 33.6 mt∕ km2 (0.15 U.S. t/acre) in the Big Bear Creek Subbasin to 88.4 mt∕ km2 (0.39 U.S. t/acre) in the Middle Potlatch Creek Subbasin representing 2.3–7.7% of the total surface sediment load. An erosion potential index was proposed to assist resource managers predict gully locations at the watershed scale using readily available remote sensing and geographic information system layers.

Development of Storm-Water Management Design Criteria to Maintain Geomorphic Stability in Kansas City Metropolitan Area Streams

Fifty-three years of historical precipitation data were applied to the U.S. Environmental Protection Agency Storm Water Management Model (SWMM) to conduct hydrologic and hydraulic simulations, generating continuous stream flow hydrographs in the receiving stream channels. On-site BMP and regional detention criteria were selected to allow postdevelopment replication of predevelopment peak flow frequency exceedance curves and the critical portions of shear stress duration curves. Instream continuous stage data generated by SWMM were used to examine erosion potential through the use of an erosion potential index. Coarse stream bed material were found to be less sensitive to changes in erosion potential due to urbanization, and extended detention ponds designed for flood control and water quality treatment were effective in reducing erosion potential. These controls were less effective in reducing erosion potential of fine loam bed material, indicating reductions of runoff volumes are required to minimize increases in channel erosion. Findings indicate that regional analysis based on local hydrologic and geomorphic characteristics are necessary to identify appropriate storm-water control requirements.

Hydrologic, water quality and geomorphic indicators of catchment Effective Imperviousness

Recent research has related waterway ecosystem health to a simple composite indicator of catchment Effective Imperviousness (EI). EI is defined as the impervious area that is directly connected, via a stormwater pipe or channel, to receiving waters. Empirical evidence has shown that catchments with EI greater than 5% have a significant impact on stream health. There are many hydrological and water quality indicators that could be used to define the EI of a catchment. Three primary indicators are proposed. Templates relating each of these indicators to catchment imperviousness were derived to enable (i) stormwater management strategies to be assessed in terms of catchment EI; and (ii) to examine the performance of current Victorian Best Practice Environmental Management (BPEM) objectives for stormwater. Meeting the current Victorian BPEM objectives has the effect of transforming the pollutant characteristics of a catchment of 60% imperviousness to an equivalent catchment with an EI of 10% or less. Rainwater tanks transform the hydrologic characteristics of a catchment to a lower equivalent EI, reducing a catchment with an EI of 60% to between 40% and 50%. Further reduction in catchment EI may be achieved by a combination of larger tank volume, higher stormwater use as a source and stormwater infiltration. Analyses also suggest that Victorian BPEM objectives for 1.5-year ARI peak flow reduction can significantly reduce the post-development Erosion Potential Index (EPI) of natural urban waterways by as much as 90%. This paper demonstrates that meeting the current Victorian BPEM objectives could contribute substantially to achieving low catchment EI.

Matching the critical portion of the flow duration curve to minimise changes in modelled excess shear

Hydrologic and hydraulic modeling in the USEPA Stormwater Management Model (SWMM) were used to examine the effectiveness of typical stormwater management practices in reducing the potential for stream erosion. Fifty-year continuous simulations were used to produce flow duration curves and stream erosion rates for a variety of critical shear stress values representative of both cohesive and non-cohesive sediments. An excess shear stress erosion potential index was used to evaluate changes in erosion between undeveloped conditions of a 10 hectare watershed and four variations of post-development stormwater control. Evaluation of flow duration curves showed that when development takes place, the duration of mid- to low-range discharges increase significantly, especially when detention practices are applied. In channels with low entrainment thresholds for bed and bank materials, e.g. sands and highly erodible clays, the significant increase of the duration of mid- to low-range discharges results in erosion potential index values greater than two regardless of the detention practices used. Overcontrol detention resulted in erosion potential index values of less than one, indicating a loss of erosion potential for bed materials such as most gravels (d(s) > 6 mm) and resistant clays that have critical shear stress values greater than four Pa.