Design Of Vegetative Filter Strips Research Articles

Effectiveness of vegetative filter strips for sediment control from steep construction landscapes

Sediment carried off-site by runoff poses a significant water quality threat to receiving water bodies. Best management practices (BMPs) are commonly applied to reduce the impact of runoff on surface water quality. Vegetative filter strips (VFS) are low-cost BMP that often provide significant runoff mitigation in agricultural and urban settings with moderate slopes (<15 %). However, the runoff mitigation effectiveness of VFS under steep, short slopes like those typical of roadway construction is unknown. This study aimed to systematically investigate the efficacy of short (<5 m) and sparse VFS on steep slopes (>15 %). Field experiments were conducted on a steep hillslope (3H:1V, 33.3 %) where three VFS lengths (1.52 m, 3.05 m, and 4.57 m) were monitored during runoff events (10-y, 6-hr) to measure runoff delivery ratio (RDR) and sediment delivery ratio (SDR). The experimental results showed reductions of 60–98 % in runoff and 73–98 % in sediment, confirming the potential efficiency of this BMP in high-sloped conditions like a roadway construction site under certain conditions. The Vegetative Filter Strips Modeling System (VFSMOD) was successfully tested against the observed field values (NSE = 0.98 and 0.89 for RDR and SDR, respectively) and used to explore more scenarios. A wide range of roadway construction settings (VFS size, slope, vegetation density) was investigated with VFSMOD, and two simplified statistical regression equations and nomographs were developed to quantify RDR and SDR based on the simulation results. The proposed equations simplify the complexity of VFS design and can be readily generalized to other locations (rainfall/runoff, soil, vegetation) after reparametrizing coefficients in regression equations based on VFSMOD simulations to obtain new nomographs as a design aid to determine the minimum buffer length for a particular site.

Modelling sediment trapping in vegetative filter strips on steep slopes

AbstractThe slope effects on sediment trapping process in vegetative filter strips (VFS) are usually neglected in current modelling practices for VFS operation, which hamper the VFS design and performance evaluation, especially on steep slopes. To fill the knowledge gap, 12 laboratory experiments of sediment trapping in VFS were conducted with three different inflow discharge (80, 100, and 120 ml s−1) and four slope angles (5,10, 15, and 20°). The experimental results show that, on steep slopes (10, 15, and 20°), a part of trapped sediment particles in VFS can be eroded again and then dragged to the downstream as bed load, whilst they do not move on gentle slope (5°). To describe the complex processes, a simple and effective modelling framework was developed for sloped VFS by coupling the slope infiltration, runoff, and modified sediment transport model. The model was tested against the experimental results and good agreements between the modelled and observed results were found in both runoff and sediment transport processes for all cases. On steep slopes, the sediment trapping performance of VFS decreases significantly because the erosion of deposited sediment particles can account for more than 60% of the sediment load in the outflow. The slope effect on sediment trapping efficiency of VFS varies greatly with soil, VFS, and slope properties. The model was compared with previous sediment transport equation and found that both methods can satisfactorily predict the sediment trapping of VFS on gentle slopes, but previous sediment transport equation is likely to overestimate the sediment trapping efficiency in VFS on steep slopes. This model is expected to provide a more realistic and accurate method for predicting runoff and sediment reduction in VFS on sloping surfaces.

Metamodeling methods that incorporate qualitative variables for improved design of vegetative filter strips

Significant amounts of pollutant are measured in surface water, their presence due in part to the use of pesticides in agriculture. One solution to limit pesticide transfer by surface runoff is to implement vegetative filter strips. The sizing of VFSs is a major issue, with influencing factors that include local conditions (climate, soil, vegetation). The BUVARD modeling toolkit was developed to design VFSs throughout France according to these properties. This toolkit includes the numerical model VFSMOD, which quantifies dynamic effects of VFS on site-specific pesticide mitigation efficiency. In this paper, a metamodeling, or model dimension reduction, approach is proposed to ease the use of BUVARD and to help users design VFSs that are adapted to specific contexts. Three different reduced models, or surrogates, are compared: a linear model, GAM, and kriging. It is shown that kriging, implemented with a covariance kernel for a mixture of qualitative and quantitative inputs, outperforms the other metamodels. The metamodel is a way of providing a relevant first approximation to help design the pollution reduction device. In addition, it is a relevant tool to visualize the impact that lack of knowledge of some field parameters can have when performing pollution risk analysis and management.

Using ArcGIS hydrologic modeling and LiDAR digital elevation data to evaluate surface runoff interception performance of riparian vegetative filter strip buffers in central Iowa

The Midwest is well known for agriculture, and Iowa is a leader in corn (Zea mays L.) and soybean (Glycine max [L.] Merr.) production. Fertilizers and chemical pesticides used to increase crop production can adversely affect the soil and water health. Midwest farmers also produce livestock and graze cattle on pastureland that can lead to excessive surface runoff and soil erosion. Establishing vegetative filter strips (VFSs) along the edge of farmland is one of the best management practices (BMPs) to reduce nutrient and sediment loss. However, studies have revealed that the classic VFS design along the length of an agricultural field does not adequately address nonuniform flow through the buffer. New designs are being researched to increase the efficiency of the VFS. In order to accurately implement new design strategies, the runoff flowpaths into the VFS need to be accurately modeled. This research assesses the performance of existing established VFS buffers of selected sites by modeling and analyzing the flow accumulation from the field into the VFS using geographic information system (GIS) and light detection and ranging (LiDAR) derived digital elevation model (DEM) 5 × 5 m data. This study also employed the new coefficient of flow interception (CFI) approach that improves the process of identifying areas where flow is concentrated and designing more efficient filter strips to account for concentrated runoff. In this study, the performance of VFS in three sites was evaluated by developing and using the CFI. Among the three sites, site 1 had very poor efficiency and no flow passes through the VFS, site 2 had low efficiency, and site 3 had excellent efficiency.

Optimization Models for the Design of Vegetative Filter Strips for Stormwater Runoff and Sediment Control

Vegetative filter strips (VFS) are an effective methodology for runoff management and control of sediment flow and soil erosion, particularly for large urban parking lots, and for irrigation water management. An optimization model for the design of vegetative filter strips for runoff management, that minimizes the amount of land required for the strips, is developed herein. The resulting optimization model is based upon the kinematic wave equation for overland sheet flow along with equations defining the cumulative infiltration and infiltration rate. The nonlinear programming (NLP) optimization model has been applied using the General Algebraic Modeling System (GAMS). The runoff management model is extended for the control of sediment. These new models provide flexibility for site-specific conditions and are a step forward in the development of new design methodologies for stormwater and irrigation flow management. The optimization models have been applied using a sensitivity analysis of parameters such as different soil types, rainfall characteristics etc., performed to validate the model. Results of the example model applications indicate the usefulness of the models for practical applications in the field. To our knowledge this is the first optimization model developed for the design of vegetative filter strips for runoff and sediment control.

Dynamics of runoff and sediment trapping performance of vegetative filter strips: Run-on experiments and modeling

Vegetative filter strips (VFSs) are a labor-saving and cost-effective agricultural best management practice to trap water runoff and sediment from the source areas. They also provide forage and/or fuel and are therefore potentially profitable for land owners. VFSs are however a dynamic system: the runoff delivery ratio (RDR) and sediment delivery ratio (SDR) vary with growth stage and vegetation types. The impacts of vegetation characteristics as well as soil physical properties modified by vegetation growth, on the RDR and SDR of VFS were evaluated by a flume experiment. Two plant species (cocksfoot (Dactylis glomerata L.) and white clover (Trifolium repens L.)) were tested at three stages in the growing season of 2016 (May, July, and August). The measured RDR and SDR were compared with the simulated results from Vegetative Filter Strip Modeling System (VFSMOD). In the early stages of the growing season, the cocksfoot formed a dense network of stems with high strip Manning's roughness faster than white clover. The runoff and sediment trapping effects of the white clover VFS were greater than that of cocksfoot VFS in all the three stages (lower RDR and SDR). This is likely attributed to strongly tillering, creeping stem posture and high infiltration capacity of the white clover VFS. VFSMOD simulated the RDR and SDR reliably except under low vegetation coverage conditions (white clover in May). The results suggested that (1) both soil physical properties and vegetation characteristics should be considered for the species-specific, temporally variable performance of VFS; and (2) when using VFSMOD inform the VFS design, modelers should take the dynamics of vegetation, mainly through vertical saturated hydraulic conductivity, stem spacing and strip Manning's roughness into account, and select parameters that reflect the actual field conditions.

A modeling approach to determining the relationship between vegetative filter strip design and sediment composition

Vegetative filter strips (VFS) are areas of either planted or indigenous established vegetation designed to improve the quality of surface runoff. They can be incorporated into pastures, grassed waterways, terraces, or cropland to remove sediment, nitrogen, or phosphorus from runoff. However, their trapping efficiencies depend mainly on the sediment characteristics. The finer soil particles pass through the filter more easily and have more surface area, accounting for most of the transported sediment-bound pollutants. Therefore, the objective of this study was to use a modeling approach to develop a Sediment Composition Vegetative Filter Strip (SCVFS) model to predict the clay, silt and sand trapping efficiencies of VFS based on a wide range of soil loss data from Central Chile. The physically based Water Erosion Prediction Project (WEPP) model was implemented using actual soil and climate data from Central Chile to generate a soil loss database for many VFS designs. More than 22,000 erosion events were generated with data from 28 sites. Three nonlinear relationships were developed between clay, silt and sand delivery and VFS length. The clay and silt models provided accurate estimates compared to WEPP for the calibration (R2=0.80–0.87) and validation (R2=0.73–0.80) sites. However, the sand estimates were not correlated to WEPP (R2=0.00–0.18), as the model computes sand using the difference between the total predicted sediments (R2=0.77–0.89) and the clay and silt estimates. Nevertheless, because most of the sediment-bound pollutants move with the finer sediments, this is not a modeling limitation. Compared to other physically based VFS models, the SCVFS model is remarkably easy to use because it only requires the characteristics of the sediment delivery when there is no filter, the rainfall erosivity and the hillslope and filter lengths. Additionally, it can be easily combined with many existing erosion models that provide daily soil loss estimates, making it a flexible VFS design tool. This study provides the detailed methodology to construct this model and discusses its advantages and limitations.

Sediment deposition and overland flow hydraulics in simulated vegetative filter strips under varying vegetation covers

Vegetative filter strips (VFSs) can effectively trap sediment in overland flow, but little information is available on its performance in controlling high-concentration sediment and the runoff hydraulics in VFS. Flume experiments were conducted to investigate the sediment deposition, hydraulics of overland flow and their relationships in simulating VFS under a great range of sediment concentrations with four levels of vegetation cover (bare slope and 4%, 11% and 17%) and two flow rates (15 and 30 L min−1). Sediment concentrations varied from 30 to 400 kg m−3 and slope gradient was 9°. Both the deposited sediment load and deposition efficiency in VFS increased as the vegetation cover increased. Sediment concentration had a positive effect on the deposited load but no effect on deposition efficiency. A lower flow rate corresponded to greater deposition efficiency but had little effect on deposited load. Flow velocities decreased as vegetation cover increased. Sediment concentration had a negative effect on the mean velocity but no effect on surface velocity. Hydraulic resistance increased as the vegetation cover and sediment concentration increased. Sediment deposition efficiency had a much more pronounced relationship with overland flow hydraulics compared with deposited load, especially with the mean flow velocity, and there was a power relationship between them. Flow regime also affected the sediment deposition efficiency, and the efficiency was much higher under subcritical than supercritical flow. The results will be useful for the design of VFS and the control of sediment flowing into rivers in areas with serious soil erosion. Copyright © 2015 John Wiley & Sons, Ltd.

Can vegetative filter strips efficiently trap trace elements during water erosion events? A flume experiment with contaminated sediments

Soils polluted with trace elements can become sources of pollution for surrounding soil and water resources as a result of dispersion of contaminated soil particles by water erosion. Vegetative filter strips (VFS) implemented downstream of the source of pollution may be used to trap sediments and their associated contaminants. An experimental flume was designed in order to test the potential of Lolium perenne and Trifolium repens VFS to retain sediment contaminated by As and Pb (Ath) or Zn and Cd (Prayon). T. repens with its creeping posture and large leaves had a higher sediment retention efficiency (SRE=47%) than L. perenne with an erect posture (SRE=26%). Sedimentation upstream of and in the strip led to the selective retention of coarse particles and an enrichment in fine soil particles at the outlet of the flume. This effect was most marked for the T. repens VFS compared to L. perenne and bare soil. Consequently, for the Prayon soil, the retention efficiency of Cd in T. repens VFS (53%) was higher than the SRE (48%) because Cd concentrations were 3 times higher in the sand fraction than in the clay fraction. On the contrary, the retention of Zn (48%), which was distributed more homogeneously across particle size fractions, was similar to the SRE. For Ath, the retention of both As (26%) and Pb (11%) in the T. repens VFS was lower than the SRE (46%) because both trace elements were preferentially associated with clay size particles. Trace element retention efficiency of VFS may thus be higher or lower than the SRE depending on the distribution of trace elements among particle size classes. This must be taken into account in the proper design of VFS aimed at controlling off-site pollution by trace element-contaminated sediments.

Development of Web GIS-Based VFSMOD System with Three Modules for Effective Vegetative Filter Strip Design

In recent years, Non-Point Source Pollution has been rising as a significant environmental issue. The sediment-laden water problem is causing serious impacts on river ecosystems not only in South Korea but also in most countries. The vegetative filter strip (VFS) has been thought to be one of the most effective methods to reduce the transport of sediment to down-gradient area. However, the effective width of the VFS first needs to be determined before VFS installation in the field. To provide an easy-to-use interface with a scientific VFS modeling engine, the Web GIS-based VFSMOD system was developed in this study. The Web GIS-based VFSMOD uses the UH and VFSM executable programs from the VFSMOD-w model as core engines to simulate rainfall-runoff and sediment trapping. To provide soil information for a point of interest, the Google Map interface to the MapServer soil database system was developed using the Google Map API, Javascript, Perl/CGI, and Oracle DB programming. Three modules of the Web GIS-based VFSMOD system were developed for various VFS designs under single storm, multiple storm, and long-term period scenarios. These modules in the Web GIS-based VFSMOD system were applied to the study watershed in South Korea and these were proven as efficient tools for the VFS design for various purposes.

Performance Evaluation of Three Vegetative Filter Strip Designs for Controlling Feedlot Runoff Pollution

A vegetative filter strip (VFS) is designed to reduce transport of sediments and nutrients downstream mainly through settling, infiltration (into soil profile), adsorption (to soil and plant materials), and by plant uptake. However, the performance of a VFS greatly depends on a VFS design and climatic conditions of a region. In this paper, relative performance of three VFSs (hereafter Cass County-CC, Sargent County-SC, and Richland County-RC buffers) was evaluated and compared in the context of VFS design for feedlot runoff pollution control and management under agro-climatic condition of North Dakota. Buffer at CC feedlot was established with broadleaf or common cattail (Typha latifolia) grass filter, SC feedlot buffer had Garrison creeping foxtail (Alopecurus arundinaceus Poir.) and reed canary grass (Phalaris arundinaceus), and RC feedlot buffer had mixed grasses. Automatic samplers were installed to collect runoff samples at each inflow and outflow locations. Collected runoff samples were analyzed for total suspended solids (TSS), ortho-phosphorus (ortho-P), total phosphorus (TP), ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N), total Kjeldahl nitrogen (TKN), total nitrogen (TN), and potassium (K). Cass County (CC) VFS with cattails grass filter had the longest runoff-flow length (65 m) and resulted in better conducive environment for restricted TSS and TP transports reduction and better adsorption of ortho-P, NH4-N, and K compared to SC and RC feedlot buffers. Overall TSS, ortho-P, TP, NH4-N, and K removal efficacies were 88%, 90%, 89%, 91% , and 90%, respectively, at CC VFS. At SC feedlot VFS resulted in the highest NO3-N reduction. Relatively poor performance was observed for the RC feedlot which was due to smaller runoff-flow length (12 m). Overall, CC feedlot outperformed the SC and RC VFSs in respect of TSS, ortho-P, TP, NH4-N, TKN/TN transport reductions.

Distinct influence of filter strips on acute and chronic pesticide aquatic environmental exposure assessments across U.S. EPA scenarios

Vegetative filter strips (VFS) are proposed for protection of receiving water bodies and aquatic organisms from pesticides in runoff, but there is debate regarding the efficiency and filter size requirements. This debate is largely due to the belief that no quantitative methodology exists for predicting runoff buffer efficiency when conducting acute and/or chronic environmental exposure assessments. Previous research has proposed a modeling approach that links the U.S. Environmental Protection Agency’s (EPA’s) PRZM/EXAMS with a well-tested process-based model for VFS (VFSMOD). In this research, we apply the modeling framework to determine (1) the most important input factors for quantifying mass reductions of pesticides by VFS in aquatic exposure assessments relative to three distinct U.S. EPA scenarios encompassing a wide range of conditions; (2) the expected range in percent reductions in acute and chronic estimated environmental concentrations (EECs); and (3) the differential influence of VFS when conducting acute versus chronic exposure assessments. This research utilized three, 30-yr U.S. EPA scenarios: Illinois corn, California tomato, and Oregon wheat. A global sensitivity analysis (GSA) method identified the most important input factors based on discrete uniform probability distributions for five input factors: VFS length (VL), organic-carbon sorption coefficient (Koc), half-lives in both water and soil phases, and application timing. For percent reductions in acute and chronic EECs, VL and application timing were consistently the most important input factors independent of EPA scenario. The potential ranges in acute and chronic EECs varied as a function of EPA scenario and application timing. Reductions in acute EECs were typically less than percent reductions in chronic EECs because acute exposure was driven primarily by large individual rainfall and runon events. Importantly, generic specification of VFS design characteristics equal across scenarios should be avoided. The revised pesticide assessment modeling framework offers the ability to elucidate the complex and non-linear relationships that can inform targeted VFS design specifications.

Escherichia coli Load Reduction from Runoff by Vegetative Filter Strips: A Laboratory-Scale Study

Vegetative filter strips (VFS) are commonly used best management practices for removing contaminants from runoff. Additional research is warranted to determine their efficiency and the most appropriate metrics for predicting fecal bacteria reductions. The objective of this research was to determine VFS effectiveness in removing from runoff relative to inflow rate, infiltration capacity, and flow concentration. This research also investigated the presence of in runoff from clean water runon after diluted manure runon events. A laboratory-scale VFS soil box (200 cm long, 100 cm wide, 7.5% slope) was packed with a sandy loam soil. Ten constant-flow VFS experiments were conducted with and without vegetation (8-10 cm ryegrass [ L.]) at low (20-40 cm s), medium (40-60 cm s), and high (85-120 cm s) flow rates and for a full (100 cm) or concentrated (40 cm) VFS flow width to simulate a channelizing flow condition. Two runon events were investigated for each experimental condition: (i) diluted liquid swine manure runon and (ii) clean water runon 48 h afterward. was used as an indicator of fecal contamination and was quantified by the most probable number (MPN) technique. No concentration reductions were observed based on peak outflow concentrations, and only small concentration reductions were observed based on outflow event mean concentrations. The mass reductions ranged from 22 to 71% and were strongly correlated to infiltration or runoff reduction ( = 0.88), which was dependent on the degree of flow concentration. Little to no effect of sedimentation on transport was observed, hypothesized to be due to minimum attachment to sediment particles because the bacteria originated from manure sources. Therefore, the design of VFS for bacteria removal should be based on the infiltration capacity in the VFS and should prevent concentrated flow, which limits total infiltration. The event mean concentrations in clean water runon experiments were between 10 and 100 MPN per 100 mL; therefore, under these conditions, VFS served as a source of residual from previous runon events.

GDVFS: A New Toolkit for Analysis and Design of Vegetative Filter Strips Using VFSMOD

Abstract The Guelph design tool for vegetative filter strips, GDVFS, is a toolkit for the analysis and design of vegetative filter strips (VFSs). The upland hydrology model UH and the vegetative filter strip model VFSMOD (the two main components of GDVFS) were adopted from an existing interface (VFSMOD-W), and new nutrient and bacteria transport add-ons for UH and VFSMOD were incorporated into GDVFS. Other utilities and tools were also included in GDVFS to provide a capable toolkit for the analysis and design of VFSs. The published evaluation of computational procedures used in GDVFS indicates that these procedures perform very well in the estimation of VFS sediment and phosphorus removal efficiencies. According to these results, comparison of the predicted and observed values for sediment and phosphorus removal efficiencies indicates 10 and 20% error, respectively. This paper provides descriptions on the capabilities and methodology followed in the GDVFS toolkit.

Performance of Vegetative Filter Strips with Varying Pollutant Source and Filter Strip Lengths

Vegetative filter strips (VFS) can reduce runoff losses of pollutants such as nitrogen (N) and phosphorus (P) from land areas treated with fertilizers. While VFS effectiveness is considered to depend on lengths of pollutant source and VFS areas, there is little experimental evidence of this dependence, particularly when the pollutant source is manure-treated pasture. This study assessed the effects of pollutant source area (fescue pasture treated with poultry litter) length and VFS (fescue pasture) length on VFS removal of nitrate N (NO3-N), ammonia N (NH3-N), total Kjeldahl N (TKN), ortho-P (PO4-P), total P (TP), total organic carbon (TOC), total suspended solids (TSS), and fecal coliform (FC) from incoming runoff. This research examined poultry litter-treated lengths of 6.1, 12.2, and 18.3 m, with corresponding VFS lengths of up to 18.3 m, 12.2 m, and 6.1 m, respectively. Runoff was produced from simulated rainfall applied to both the litter-treated and VFS areas at 50 mm/h for 1 h of runoff. Pollutant concentrations in runoff were unaffected by litter-treated length but demonstrated a first-order exponential decline with increasing VFS length except for TSS and FC. Runoff mass transport of NH3-N,TKN, PO4-P, TP and TOC increased with increasing litter-treated length (due to increased runoff) and decreased (approximately first-order exponential decline) with increasing VFS length when affected by VFS length. Effectiveness of the VFS in terms of NH3-N, TKN, PO4-P, TP and TOC removal from runoff ranged from 12-75, 22-67, 22-82, 21-66, and 8-30% respectively. The data from this study can help in developing and testing models that simulate VFS performance and thus aid in the design of VFS installed downslope of pasture areas treated with animal manure.

Vegetative Filter Strip Design for Grassed Areas Treated with Animal Manures

Vegetative filter strips (VFS) are a low-cost management option that have been demonstrated to be effective in reducing runoff transport of fertilizer constituents applied to grassed areas (pasture or meadow). Runoff quality studies involving fertilizers applied to grassed areas suggest that VFS can be designed by assuming that (1) only infiltration is responsible for pollutant removal, (2) the first post-application runoff event is most important from a water quality perspective (enabling a design event approach), and (3) no pollutant build-up that degrades VFS performance will occur. The purpose of this study was to develop a VFS design algorithm for grassed areas that uses available information on the water quality dynamics of these systems to simplify the design process to the greatest degree practical. The design algorithm consists of the SCS (1972) Curve Number method for runoff estimation and the Overcash et al. (1981) equation for predicting concentrations of pollutants exiting a VFS as a function of VFS and runoff parameters. The procedure can be used to determine the VFS length required to meet either an allowable pollutant runoff concentration or allowable pollutant mass transport. As an alternative, the process can be used to determine VFS length required to achieve given relative reductions in incoming pollutant runoff concentrations and mass transport. This algorithm can be used quickly and with minimal data to determine the VFS length requirement necessary to provide any desired degree of effectiveness given inputs such as incoming pollutant runoff concentration, background pollutant runoff concentration, soil hydrologic properties, and design storm parameters. Charts are presented that eliminate the need for computations in selected cases.