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Abstract: Grass swales and filter strips are among the simplest and most cost-effective form of stormwater control measures. Despite this, relatively few controlled studies have been undertaken to assess their performance, and very few models are available to predict their efficiency. This paper focuses on field performance of grass filters in removal of total suspended solids (TSS) from overland flow, and verification of TRAVA, a model of sediment behaviour in grass filters (published earlier in Deletic, A., 2001. Modelling of water and sediment transport over grassed areas. Journal of Hydrology 248, 168–182; Deletic, A., 2005. Sediment behaviour in runoff over grassed surfaces. Journal of Hydrology 301, 108–122). Limited nutrient removal data were collected, at one of the field sites. The paper presents results from controlled field tests undertaken on a grass filter strip in Aberdeen, Scotland, and a grass swale in Brisbane, Australia. In both studies TSS concentrations were recorded along the grass, for artificial inflow of water and sediment of different flow rates and sediment concentrations. In the Aberdeen study the emphasis was on performance in relation to different sediment particle sizes, while for the Brisbane swale, treatment performance for total nitrogen (TN), and total phosphorus (TP) were also recorded. Both experimental programmes had an unsteady input of pollutants. The Aberdeen strip reduced sediment inflow concentrations by 61–86%, whilst the Brisbane swale removed an average of 69, 46, and 56% of the total loads of TSS, TP and TN, respectively. TRAVA was used to model both the strip and swale. For the Aberdeen strip, the differences between the measured and modelled sediment loading rates were within ±25% of measured. Modelled concentrations in outflow from the Brisbane swale were within ±17% of measured. The predicted mass of total sediment removed during experiments was within ±50% of measured for the Aberdeen strip and ±11% for the Brisbane swale. TRAVA is therefore shown to be a reliable tool for prediction of the performance of grass filters used for stormwater treatment. [Copyright &y& Elsevier]

• TELEMAC-2D model was developed to assess morphodynamics in Soai Rap, Vietnam. • Mining sites were setup as specific mined volumes over time. • Dredging efficiently reduces the largest sediment deposition zone upstream. • Deposition increased substantially in the river mouth due to dredging. Recent riverbed sand mining activities have modified estuarine morphology and sedimentation patterns in many Southeast Asian deltas. The Soai Rap Estuary along the Dong Nai River (one of the largest rivers in Southern Vietnam) is one of the most intensively mined areas in the region, where large-scale sand mining activities have started since the 1990′s. In this paper, we used hydrodynamic modelling (TELEMAC-2D) to investigate the estuarine morphological changes and sediment dynamics related to the intensive riverbed mining in the Soai Rap Estuary. After the hydraulic calibration and validation of the model, we simulate four scenarios: two with dredging, one with sand excavation, and a baseline condition. Our results show that dredging substantially changed the hydraulic regimes, morphological and sediment dynamics of the estuary. Compared to the baseline, dredging substantially influences flow velocity and tidal amplitude. These activities reduce the amount of sediment accumulating upstream by 18% to 36%, while increasing sediment deposition in the Soai Rap Estuary by 6% to 13%. Furthermore, sediment accumulation in the Ganh Rai Bay area decrease by 5% to 10% due to increased sediment transport from the sea to the estuary. Our modelled results also show that the mining pits (pockmarks) created by sand extractions efficiently trap sediment, causing discontinuities in the longitudinal transport of sediment and resulting morphological patterns. We conclude that the morphology and sediment transport regime of the Soai Rap estuary has been significantly altered by the river sand dredging. As such, we recommend that the local government put in place measures to ensure that sand extraction is carried out sustainably in the future, to minimise further alterations to the natural sedimentation patterns and geomorphology of this estuary. [ABSTRACT FROM AUTHOR]

Summary: This paper presents the development of expert system related models using the concepts of Geno-Kalman Filtering (GKF) and fuzzy logic to predict the concentration of total suspended solids (TSS) with the input of wind speed at the locations of Cat Point and Dry Bar in Apalachicola Bay, USA. The TSS and wind speed data recorded from June 1, 2005 to July 30, 2005 are used for the present modeling study. Data set is divided into two parts for the model development. The June data are selected for calibration and the July data are for model verification. The predicted TSS concentrations from the Geno-Kalman Filtering and fuzzy logic models are compared with those from a hydrodynamic model and measured data reported in . The statistical values in terms of the mean squared error (MSE), the coefficient of efficiency (CE) and the chi-square (χ 2) parameter between the observed data and predicted results for the evaluation of each model’s performance are presented. It is noted that both the hydrodynamic and Geno-Kalman Filtering models are capable of predicting TSS concentration with the trend of dynamic variation. Although the fuzzy logic and the Geno-Kalman Filtering models outperform the hydrodynamic model, the Geno-Kalman Filtering model is found to be able to produce the most accurate results at the studied locations. The fuzzy logic model tends to under-predict the TSS concentrations. [ABSTRACT FROM AUTHOR]

Summary: In many agricultural regions investments are made into improved land management and catchment restoration with the aim of reducing sediment and nutrient delivery to downstream water bodies. This paper presents the results of an 8year field study that evaluated the impact of improved grazing land management (GLM) on a 14km2 sub-catchment of the Burdekin River in northern Australia. Land condition recovery and changes to runoff and sediment yield were measured on hillslopes (using three flumes) and at the end of the catchment (using automatic water sampling). Ground cover was monitored at the beginning of the wet season at hillslope and catchment scales using direct measurement and Quickbird satellite imagery. At the catchment scale, improved GLM resulted in an increase in mean ground cover between 2003 and 2007, relative to a control grazing property. However, the total suspended sediment yield from hillslopes did not decline due to the disproportionately high yields from low (<10%) cover sites particularly in high runoff years. In 2007, when there was above-average rainfall, 97% of the hillslope derived fine sediment was coming from less than 3% of the catchment. Catchment sediment yield also increased, associated with higher rainfall and runoff in latter years of the study. In years of above-average rainfall, it is estimated that less than 40% of catchment sediment yield was derived from hillslope erosion. Channel erosion is considered to contribute the remaining sediment. Rehabilitation of hillslope scalds and gullies is likely to be an important companion to improved GLM to reduce catchment fine sediment yields in this landscape. Evaluation of gully and hillslope scald rehabilitation techniques is required, including the economic feasibility of such options. [Copyright &y& Elsevier]

Summary: Poor land condition resulting from unsustainable grazing practices can reduce enterprise profitability and increase water, sediment and associated nutrient runoff from properties and catchments. This paper presents the results of a 6year field study that used a series of hillslope flume experiments to evaluate the impact of improved grazing land management (GLM) on hillslope runoff and sediment yields. The study was carried out on a commercial grazing property in a catchment draining to the Burdekin River in northern Australia. During this study average ground cover on hillslopes increased from ∼35% to ∼75%, although average biomass and litter levels are still relatively low for this landscape type (∼60 increasing to 1100kg of dry matter per hectare). Pasture recovery was greatest on the upper and middle parts of hillslopes. Areas that did not respond to the improved grazing management had <10% cover and were on the lower slopes associated with the location of sodic soil and the initiation of gullies. Comparison of ground cover changes and soil conditions with adjacent properties suggest that grazing management, and not just improved rainfall conditions, were responsible for the improvements in ground cover in this study. The ground cover improvements resulted in progressively lower runoff coefficients for the first event in each wet season, however, runoff coefficients were not reduced at the annual time scale. The hillslope annual sediment yields declined by ∼70% on two out of three hillslopes, although where bare patches (with <10% cover) were connected to gullies and streams, annual sediment yields increased in response to higher rainfall in latter years of the study. It appears that bare patches are the primary source areas for both runoff and erosion on these hillslopes. Achieving further reductions in runoff and erosion in these landscapes may require management practices that improve ground cover and biomass in bare areas, particularly when they are located adjacent to concentrated drainage lines. [Copyright &y& Elsevier]

Abstract: Estimation of sediment and nutrient loads is of crucial interest for a good assessment of water pollution. This paper proposes an overview of existing estimation methods and a framework to select the most suited one given available streamflow and concentration data. Correlations between contaminant concentration and streamflow should first be checked to generate missing concentration values by regression. However, correlations are not always strong, in which case the ratio estimator method is more appropriate. Given a 6-year data set (1989–1995) from the Beaurivage River (Québec, Canada) with, at best, a weekly sampling, the ratio estimator method was selected to estimate annual and seasonal loads of sediments and nutrients (N and P). Results show relatively steady annual loads (on average 8.1 and 1.1kghayr−1 for total dissolved N and total P, respectively) and a low erosion rate (0.23thayr−1). The results also confirm that nutrient and sediment transport via runoff is essentially a springtime process in this region, and they indicate that dissolved P represents the bulk of the total P load, most likely due to artificial subsurface drainage systems in the watershed. These results are compared to the results obtained by using averaging methods and to several other sources of information from literature, confirming the order of magnitude but highlighting some remaining uncertainties. Finally, some research avenues are proposed to improve the proposed framework and to investigate other estimation methods adapted to data characteristics. [Copyright &y& Elsevier]

The author read with much interest the publication by Mize et al. (2018) on the decrease in suspended-sediment concentrations and loads in the lower Mississippi and Atchafalaya Rivers between 1980 and 2015. Researchers interested in sediment dynamics in the lower Mississippi and Atchafalaya Rivers also should be aware that sediment data previously reported for the lower Mississippi-Atchafalaya River Basin by the U.S. Geological Survey (USGS) and U.S. Army Corps of Engineers (USACE) were affected by a systematic error in the fines fraction (particle sizes less than 0.063 millimeter) of the suspended-sediment concentration. This error affected results reported from October 1973 through February 2015 for two sites on the main stem of the Mississippi River, three sites on the Atchafalaya River, one site on the Old River Outflow Channel, and one site on the Red River. The USGS and USACE identified the error and have revised the results for samples collected from October 1989 through February 2015, as reported by Norton et al. (2019a) and Norton et al. (2019b). The significant conclusions of Mize et al. (2018) and sediment loads modeled using the Weighted Regressions on Time, Discharge, and Season (WRTDS) method were unaffected by the systematic error because the models used data from unaffected sites; however, the background information provided in tables 1 and 2 of Mize et al. (2018) included references to several previous studies that contained results affected by the error. This comment paper identifies which references in Mize et al. (2018) were affected by the error and alerts readers to implications of the data revision. [ABSTRACT FROM AUTHOR]