Streambank Erosion Associated with Grazing Activities in Kentucky

Streambank Erosion Associated with Grazing Activities in Kentucky

Summary

Surveys performed at permanent cross sections within grazed pastures receiving three levels of best management practices (BMPs) have been conducted to determine the degree of stream bank erosion associated with cattle activity. Photographic documentation and GPS surveys are also being conducted to monitor changes to the stream banks. At this time, statistical models are being developed to determine the effects of different grazing practices and BMPs on stream bank erosion.

Objectives/Performance Targets

The goal of this project is the provide the agricultural community with a better understanding of the impacts of cattle grazing on stream bank erosion so as to enhance current cattle production methods on small farms in Kentucky and possibly the eastern United States. Important to note is that this project is a subset of a larger research endeavor into the grazing impacts of cattle and BMPs on the water quality of a Kentucky stream whose objectives are to 1) determine whether the provision of cultural forms of BMPs such as an alternate water source, an alternate shade source, and/or the placement of supplemental feeding areas alter cattle behavior, 2) determine if the above BMPs collectively improve water quality, 3) determine if the inclusion of a fenced riparian zone with the BMP package significantly improves water quality over the BMP package alone, and 4) educate the agricultural community, especially livestock producers, about management systems that minimize the adverse environmental effects of grazing while maintaining production levels. This particular project, in combination with the larger research endeavor of which it is a part, address two main goals of the Sustainable Agriculture Research and Education (SARE) program by providing an assessment and evaluation of animal production practices to strengthen the agricultural competitiveness of Kentucky’s cattle producers while seeking to conserve soil, water and stream habitats.

Accomplishments/Milestones

After considering reviewer comments, a few changes were made to the methods described in the proposal. Instead of developing monthly topographic maps of the streamside area, permanent cross sections were installed and are being surveyed monthly using conventional leveling techniques. GPS technology was utilized to construct plan view maps of each stream on a semi-annual basis. Permanent photo stations were installed throughout the project site to provide monthly visual documentation of stream bank changes. Finally, the topography of the research pastures combined with the wet winter months experienced in Kentucky made it impossible to continuously maintain cattle on the pasture plots throughout the winter season without causing substantial damage to the pastures from the equipment used to feed the cattle hay. Cattle were removed from the pastures in December 2002 and will be reintroduced in April 2003. Preparations are underway to monitor flow as this component may assist in analyzing the stream bank changes.

During the summer of 2001, the location of the pasture plots was identified on the University of Kentucky’s Animal Research Center (ARC) and the required high tensile electric fences were constructed. Additional water lines and four water troughs were installed during the spring of 2002. All pasture plots were completed in May 2002 and were deemed ready for cattle (Figure 1). (editor’s note: all figures and supporting data can be obtained from the original report at the Southern Region SARE office by sending an email to sueblum@griffin.uga.edu.) Future plans include the construction of alleyways to facilitate movement of the cattle from the pasture plots to handling facilities. In July 2002, staff gauges were installed, one at the edge of each pasture plot, except at the most downstream points where the two weirs are located.

The literature has documented that one of the major impacts of grazing upon water quality is stream degradation. A total of 50 stream cross sections (23 in one replication and 27 in the other) were installed at random locations. Attempts were made to install cross sections in areas that exhibited a high potential for impact from cattle use (Figure 2). Surveys of the cross sections are performed monthly. To date, ten cross sectional survey events have been conducted. A comparison of the surveys conducted at different times revealed changes in the streams and thus an estimate of the amount of soil loss of gain that has occurred between sampling dates.

Changes to the stream banks are also being monitored using RTK-GPS (Real Time Kinematic Global Positioning System). This system has the capability of measuring to within two centimeters horizontally. Both streams were surveyed with RTK-GPS during the spring of 2002, prior to the introduction of cattle (Figure 3). A second survey was performed in the fall of 2002. Subsequent surveys will be conducted on a semi-annual basis. Results of the surveys can be overlain in a geographical information system to allow for the identification of stream bank alterations associated with the presence of cattle.

Soil lost or gained was computed for each cross section location for a unit length of stream using Equation 1. First, incremental areas of soil aggradation or degradation were computed for each cross section. The number of increments depended upon the number of stations designated for each cross section. Once the incremental values were determined, they were summed to provide the total area of soil change.

Eqn. 1

The subscript i represents time and subscript j represents location. The variable E indicates elevation and the variable S indicates station. A weighted distance associated with the appropriate cross section was then multiplied by each computed area from Equation 1. The exact location of all cross sections was identified using RTK-GPS allowing for the distance between subsequent cross sections to be computed, thus providing the weighted distance (Table 1, Figure 4). Graphs of the cross sections at various points throughout the year are available at http://www.bae.uky.edu/WQ406.

A total of 30 permanent photo stations were installed in May 2002. The photo stations allow for the photographic documentation of changes at the research site. Each photo station was established such that the maximum amount of the pasture plots, and especially the streams, could be monitored. Digital images are taken at each photo station once per month, and all digital photographs are taken using the same camera and settings for purposes of uniformity (Figures 5). Collection of the images coincides with the surveying of the cross sections.

Sixteen cattle were collared in May, August and November of 2002 for a period of 28 days (Figure 6). The 28-day period was selected because this is the interval that the cattle are captured for weighing. Periodically weighing the cattle provides handlers not only with the opportunity to determine the animal’s average daily weight gain, but it also allows up-close examination of the cattle for any potential health related issues. Data is collected at 5-minute intervals allowing for a 15 day data collection period, thus the collars remained on the cattle for a portion of time even when they were not actively collecting data. Information collected from the collars will provide an understanding of the level and location of cattle activity along the riparian areas.

Cattle were weighed monthly (Table 2). Data was not collected in December 2002 because the scale malfunctioned.

A newsletter detailing the aspects of the project was created in March 2002. The newsletter is available for viewing at http://www.bae.uky.edu/WQ406. Copies of the newsletter were provided to the appropriate extension personnel within the Biosystems and Agricultural Engineering Department for distribution (Appendix A).

Three separate tours have been conducted at the University of Kentucky’s Animal Research Center that included aspects of this project. The tours included visits by 1) Dr. Nancy Cox, Associate Dean of Research in the College of Agriculture at the University of Kentucky, 2) Dr. Wendy Baldwin, Vice-President for Research at the University of Kentucky, and 3) Dr. Colien Hefferan, Administrator of Cooperative State Research, Education, and Extension Service (CSREES), United States Department of Agriculture and Dawn Riley, Director of Legislative and Intergovernmental Affairs Research, Education, and Economics, United States Department of Agriculture.

A total of 15 additional monthly cross sectional survey need to be performed. Surveys of the streams using RTK-GPS will be conducted in May and November of 2003. Photographic documentation will also be conducted during the same time period as the cross sectional surveys.

Efforts are underway to develop statistical models for evaluating the results from the cross section surveys. A newsletter will be created during Year 3 to relate the results of the project to the agricultural community through field days and the Internet. Results will also be published in a peer-reviewed journal.

Impacts and Contributions/Outcomes

This project provides information regarding the impacts of cattle grazing on stream bank erosion on two central Kentucky streams. Results from this project will assist in understanding the effectiveness of different best management strategies for conserving stream habitats located in grazed pastures.

Collaborators: