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Computer-based coupled soilscape-landform evolution models provide an avenue for estimating the erosion potential of a landform over geological timescales. They also provide tools to understand soil-landform relationships in the context of both field and modelled pedogenesis processes. In this study, we used the State Space Soil Production and Assessment Model (SSSPAM) and CAESAR-Lisflood landform evolution model to simulate the evolution of a natural catchment where soil erosion rates have been closely monitored over the last 20 years. Both models predict comparable erosion rates to that of field measurements and produce similar catchment scale geomorphological patterns. Rock content data measured in the field along two transects were compared with SSSPAM simulations at the same representative points. The results showed that SSSPAM produced similar rock content variation along the respective transects. The findings demonstrate 'SSSPAM's ability to predict catchment scale erosion and surface soil distribution. The insights demonstrated here provide confidence in the SSSPAM model for Soilscape predictions for natural, agricultural and post-mining landform assessment. [Display omitted] • SSSPAM and CAESAR-Lisflood models were used to simulate the evolution of a natural catchment. • Both models produced catchment erosion rates comparable with field observations. • SSSPAM reproduced surface rock content variation on 2 transects observed in the field. • SSSPAM also revealed a possible relationship between area, slope and soil grading. • This study demonstrates SSSPAM's ability to predict erosion and surface soil distribution. [ABSTRACT FROM AUTHOR]

• Models can account for effects of conservation measures on soil erosion dynamics in tramlines. • Contouring efficiency of tramlines captures variations in slope and sowing directions. • Increased contouring efficiencies of tramlines indicate lower runoff and soil erosion rates. • Reduced tillage indicates significantly lower runoff and soil erosion rates in tramlines. To reduce water erosion, one of the most severe land degradation processes on arable soils, conservation measures such as contour farming or reduced tillage practices can be applied. The general effectiveness of these measures on reducing soil erosion is well understood, however, little is known about the influence on tramline tracks, which have considerable impact on the transport of sediment and runoff. This study assesses the impact of reduced and conventional tillage and slope-related tramline directions on runoff and soil erosion rates at catchment level. For this purpose, a published and freely available dataset was used consisting of soil loss and runoff data modelled for a single soil erosion event considering courses and structural properties of tramlines (cf. Saggau et al., 2022). The orientation of tramlines against the slope direction was defined as contouring efficiency (Cef) and calculated by an approach that relates slope and tramline directions. Finally, results of the statistical analyses are compared with mapped soil erosion data. Results show that i) high-resolution derivation of Cef, based on tramlines, shows reasonable results in capturing variations in slope curvatures within the fields, ii) increased Cefs can significantly reduce runoff and soil erosion in tramlines and, iii) reduced tillage indicates significantly lower runoff and soil erosion rates in tramlines and cultivated areas. The results reveal that tramlines have strong interrelations with surface runoff, water connectivity and soil erosion. The consideration of tramlines in process-based models should be employed in other model approaches as it improves assessments of soil erosion risk and efficiencies of conservation measures, which are necessary in taking appropriate actions in support of soil and water conservation. [ABSTRACT FROM AUTHOR]

Eroded soil from cropland watersheds is deposited as sediment into depressional wetlands such as playas degrading their ability to provide ecosystem services. Sediment removal from these degraded playa wetlands restores water storage volume. However, the effects of this restoration practice on carbon (C) and nitrogen (N) concentrations and C sequestration potential in playas has not been determined. One of the most important wetland systems and intensively cultivated regions in North America, the Rainwater Basin (RWB) of Nebraska, contained over 4000 playas but has lost 90% of them due to agricultural activities. Our objective was to examine the effects of sediment removal on wetland C and N concentrations and determine subsequent C sequestration potential. We also were interested in determining the importance of the presence of wetlands on the landscape to C sequestration given the loss of wetlands that has occurred. We hypothesized that sediment removal might decrease C sequestration potential and that the presence of wetlands on the landscape provides important C sequestration sites. To accomplish these objectives we sampled 60 playas and their immediate watersheds (20 each from reference condition, cropland, and restored through sediment removal) in 2013 and 2014 by coring soil/sediments (mollisols) to a depth of 50 cm. Restored playas contained 29% lower C and N in the top 5 cm than in reference and cropland land uses. The C in the top 5 cm was also 36% higher in the wetland than in the watershed. There were no differences in C and N among land uses/landscape positions at depths >5 cm. However, because restored playas had sediment removed, in some cases down to the clay pan of the historic playa soil surface, on an areal basis, restored playas stored 21% more soil organic carbon (SOC) in deeper horizons (25–50 cm) than reference or cropland conditions. Overall, SOC was similar among restored, cropland and reference wetlands to a 50 cm depth, indicating that sediment removal does not have a negative effect on C sequestration potential. On average, SOC was 15% higher in playas than in adjacent uplands, demonstrating the importance of playa wetlands on the landscape to C sequestration. Results of this study have widespread applicability because depressional wetlands are the dominant wetland type in temperate agroecosystems. [ABSTRACT FROM AUTHOR]

An experimental study was conducted to evaluate the effect of drainage water recycling (DWR) on reducing nitrogen (N), phosphorus (P), and sediment losses from agricultural fields to downstream surface water bodies. The two-year study (May 2019-April 2021) was conducted at an agricultural field in eastern North Carolina, U.S.A. A reservoir existed at the site was used to store subsurface drainage and surface runoff water during wet periods and provide supplemental irrigation during dry periods of the crop growing season. On average, the reservoir retained 14% of received inflow, with a higher flow reduction in the dry year (2019–2020; 29%) than the wet year (2020–2021; 8%). The hydraulic retention time (HRT) for the reservoir was 33.8 days for the dry year and 12.4 days for the wet year. The reservoir significantly reduced the loadings of N by 47%, P by 30% and sediment by 87%. Nitrogen load reduction was primarily driven by nitrate assimilation, the dominant form of N in the reservoir. Phosphorus load reduction was attributed to Orthophosphate assimilation as the reservoir released more particulate P than received. Reductions in both water flow and species concentration contributed to nutrient load reductions. Results suggested the removal efficiency of the reservoir would be highest during the summer and early fall months when the reservoir has a smaller water volume (due to irrigation), longer HRT, and warmer temperature. This study clearly demonstrated the potential of DWR for significantly reducing N, P, and sediment losses from agricultural land to receiving surface water. Further research is needed to investigate the physical, chemical, and biological processes that occur in the storage reservoir and affect the fate and transport of nutrients and sediment. The understanding of these processes will enable optimizing the treatment efficiency of DWR, which maximizes the system's benefits and reduces construction cost. • Drainage water recycling (DWR) had significant water quality benefits. • DWR reduced losses of nitrogen by 47%, phosphorus by 30%, and sediment by 87%. • DWR treatment positively correlated with water retention time and temperature. • DWR treatment negatively correlated with reservoir water volume and inflow rate. [ABSTRACT FROM AUTHOR]

Abstract: Shellfish farming, particularly oyster farms, suffers from strong siltation phenomena which are harmful to the production of shellfish. The lack of knowledge about the impact of an oyster farm on the wave propagation and on the flow remains a significant difficulty for the comprehension of sediment transport processes in coastal zones. These effects are one of the possible sources of sedimentation. The study presented here focuses on describing finely hydrodynamical phenomena (velocity fields, turbulence parameters) around oyster tables. The analysis is based on experimental trials carried out in a flume tank on reduced models of oyster tables. Experiments highlight the flow perturbations in the near field and constitute a database for validation of numerical models developed at the same time. The model based on Navier–Stokes equations offers the possibility to study the impact of more realistic table lengths on the flow and to simulate the perturbation produced by a group of oyster tables. Both experimental and numerical results are presented in this paper. [Copyright &y& Elsevier]