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Full-Text Articles in Life Sciences

Modeling Of Sediment Trapping In A Vegetative Filter Accounting For Two-Dimensional Overland Flow, Matthew J. Helmers, Dean E. Eisenhauer, Thomas G. Franti, Michael G. Dosskey Jul 2003

Modeling Of Sediment Trapping In A Vegetative Filter Accounting For Two-Dimensional Overland Flow, Matthew J. Helmers, Dean E. Eisenhauer, Thomas G. Franti, Michael G. Dosskey

Matthew J. Helmers

Vegetative filters (VF) are used to remove sediment and other pollutants from overland flow. When modeling the hydrology of VF it is often assumed that overland flow is planar but our research indicates that it can be two-dimensional with converging and diverging pathways. Our hypothesis is that flow convergence will negatively influence the sediment trapping capability of VF. The objectives were to develop a two-dimensional modeling approach for estimating sediment trapping in VF and to investigate the impact of converging overland flow on sediment trapping by VF. In this study, the performance of a VF that has field-scale flow path ...


Assessment Of Concentrated Flow Through Riparian Buffers, Michael G. Dosskey, Matthew J. Helmers, Dean E. Eisenhauer, Thomas G. Franti, Kyle D. Hoagland Nov 2002

Assessment Of Concentrated Flow Through Riparian Buffers, Michael G. Dosskey, Matthew J. Helmers, Dean E. Eisenhauer, Thomas G. Franti, Kyle D. Hoagland

Matthew J. Helmers

Concentrated flow of surface runoff from agricultural fields may limit the capability of riparian buffers to remove pollutants. This study was conducted on four farms in southeastern Nebraska to develop a method for assessing the extent of concentrated flow in riparian buffers and for evaluating the impact that it has on sediment-trapping efficiency. Field methods consisted of mapping field runoff areas and their pathways to and through riparian buffers to streams. Mathematical relationships were developed from a model (VFSMOD) that estimates sediment-trapping efficiency from the ratio of buffer area to field runoff area. Among the farms surveyed, riparian buffers averaged ...


An Overland Flow Sampler For Use In Vegetative Filters, D. Eisenhauer, Matthew J. Helmers, J. Brothers, M. Dosskey, T. Franti, A. Boldt, B. Strahm Jul 2002

An Overland Flow Sampler For Use In Vegetative Filters, D. Eisenhauer, Matthew J. Helmers, J. Brothers, M. Dosskey, T. Franti, A. Boldt, B. Strahm

Matthew J. Helmers

Vegetative filters (VF) are used to remove contaminants from agricultural runoff and improve surface water quality. State and federal cost-share funds are available to encourage landowners to install VF. The USDA-National Conservation Buffer Initiative calls for 3.2 million km of buffers to be installed by the year 2002. Numerous experimental plot and modeling studies have quantified the removal of sediments and other non-point source (NPS) contaminants from agricultural runoff by VF. Almost all of these studies have been conducted under controlled settings, including artificial sheet flow conditions, and using expensive, labor-intensive measurement systems. There is a critical need for ...


Modeling Vegetative Filter Performance With Vfsmod, Matthew J. Helmers, Dean E. Eisenhauer, Michael G. Dosskey, Thomas G. Franti Apr 2002

Modeling Vegetative Filter Performance With Vfsmod, Matthew J. Helmers, Dean E. Eisenhauer, Michael G. Dosskey, Thomas G. Franti

Matthew J. Helmers

The model VFSMOD was used to investigate the effect of varying watershed characteristics and buffer dimensions on the sediment trapping efficiency of vegetative filters. This investigation allows for a better understanding of how watershed characteristics, buffer dimensions, and storm characteristics impact the performance of vegetative filters. Using VFSMOD, relationships that estimate sediment trapping efficiency from the ratio of filter area and field area were developed for different sites. These relationships have been applied for field assessment of concentrated flow.


Use Of Ultimate Load Theories For Design Of Drilled Shaft Sound Wall Foundations, Matthew J. Helmers Jun 1997

Use Of Ultimate Load Theories For Design Of Drilled Shaft Sound Wall Foundations, Matthew J. Helmers

Matthew J. Helmers

A study was performed to investigate the factors that affect the accuracy of the procedures used by the Virginia Department of Transportation for design of drilled shaft sound wall foundations. Field load tests were performed on eight inch and nine inch diameter drilled shafts, and the results were compared to theoretical solutions for ultimate lateral load capacity. Standard Penetration Tests were run in the field and laboratory strength tests were performed on the soils from the test sites. It was found that published correlations between blow count and friction angle for sands and gravels can be used to estimate friction ...