Lower Platte Sedimentation Study

In Fall 2008 UW-Madison graduate students—Benjamin Lee, Cory Anderson, Megan Corrado and Hoi Lai Tseung—taking a course in Sediment Processes and Engineering in Natural Channels under the direction of Professor John Hoopes undertook the problem of understanding the sedimentation in the Lower Platte River (LPR) and developing solutions to restore a stable channel in the lower Platte. This fall they completed their report with a historical account of the cause of excess sedimentation, an analysis of present sedimentation and flow rates and recommendations for establishing a stable channel in the lower Platte River. Important features of the LPR have been identified and used to propose a stable channel from the Hwy 61/35 Bridge to the Mississippi River:

• Instability in the Lower Platte River (LPR) was the result of a base level change introduced by Lock and Dam 11 in 1937;
• Low velocities in and excessive sediment supply to the LPR continue to cause sediment deposition and channel alteration principally downstream of the Banfield Bridge and probably upstream, though vertical accretion was not apparent in the field inspection;
• The channel width through the LPR appears relatively stable upstream of the Banfield Bridge and unstable downstream of the bridge, although the original LPR thalweg is evident downstream;
• The channel between the Banfield Bridge and the Hwy 61/35 Bridge cut itself off after the opening of Lock and Dam 11 to increase the bed slope and transport the sediment supplied to it;
• The slope of the LPR is about 0.000306;
• The low flow channel width at the Hwy 61/35 Bridge was 110 ft and 210 ft at the Banfield Bridge;
• The measured flow rate on November 15, 2008 was similar to the value obtained by scaling the flow at the Rockville gauge to the LPR by the ratio of drainage areas;
• The 100-year flood discharge is approximately 36,500 cfs;
• Suspended sediment is the dominant mode of transport, and medium silt is the median grain size;
• A yearly sediment supply of 80,759 tons is expected at the Rockville flow gauge, and a yearly supply of 196,211 tons is predicted to the LPR by scaling of drainage areas;
• The dominant discharge is approximately 5,500 cfs;
• A bankfull depth and width of approximately 7 ft and 140 ft, respectively, are expected for a stable channel cross section.

These data will be used to explore methods of attaining a stable channel (through methods such as parallel embankment or porous sediment fence)

Dredging of Banfield Boat Launch

Look for improvements at Banfield Park this spring when using the park and launching boats from the landing. Late last fall the boat launch area was dredged and access to the landing area was improved. This work was completed through the cooperative efforts of the Friends of the Platte River, UW-Extension, UW-Platteville students, Grant County Parks Commission and Paris Township.A

team of civil engineering students, Pat Gavinski, Brian Scott, and Pat Schultz from the University of Wisconsin-Platteville designed the improvements to Banfield Bridge Recreation Area.

The students evaluated  the launch site and erosion issues at the park and put together a very comrehensive plan to beautify the park and increase its useability. 

Well Testing Project

On the evening of May 29, 2008 over sixty local residents crowded into the commons of the Platteville Middle school to receive their individual results from our well testing project and participate in an educational program to learn about the results. Three levels of testing were offered in this program: a Basic Homeowners Package to give a good indication of overall water quality; a Heavy Metals package for those with concerns about the levels of metals in their drinking water, and a Triazine Screen which indicates the presence of pesticides in drinking water.

In total 76 Platte River watershed residents took part in the program.

The program was sponsored by The Friends of the Platte River, Southwest Badger RC&D, and UW Extension to provide residents of the watershed a ten dollar discount on their well testing.
Funding for the project was provided by the Wisconsin DNR through a River Planning Grant and a donation from Grant County Land Conservation.

Peggy Compton, our local basin educator explained the process of how water moves from the surface of the ground, into the ground, and through our wells using a ground water model.

Kevin Masarik, groundwater education specialist in the College of Natural Resources at UW-Stevens Point explained the meaning of each of the tests and remedies for people with unsafe or undesirable results. He also mapped the results by general location throughout the watershed for comparative purposes.

In general, Kevin felt the ground water in the Platte River watershed was better than he expected for the geography and land use of our region when compared to results from other watersheds in the region—good news indeed!

Watershed Tour

Over a dozen people participated in our May 19, 2007 watershed tour and had the opportunity to get to know the Platte River watershed and to learn about measures that can be taken on land and in the water to ensure high quality waters throughout the watershed.
The tour included a fish shocking demonstration hosted by the Wisconsin DNR.

A big thanks goes out to all the folks who shared their knowledge on the tour: Bradd Sims and Jim Amrhein, WDNR, Steven Bertjens, USDA, Kevin Lange, Grant County Land Conservation, David Wilson, Driftless Area Initiative, Mark Sethne, UWP geography.

A portion of the tour included visiting several farms in the watershed where farmers are employing conservation measures which result in less soil erosion and cleaner streams and rivers.

The following is a list of some of the conservation features observed:

Contour Strip-Cropping: Planting crops along the contour of the hillside prevents soil from running down the hillside and entering streams when it rains. Rows of alfalfa and other perennials catch the soil as it moves down the hillside from other more erodible crops.

No-Till Cropping: By not plowing the crop residue into the soil after harvest, it is left on the fields to hold soil in place to prevent rain from washing it into streams. Crop residues help protect the soil surface from the impact of a raindrop so the soil particles do not dislodge and erode. No-till farming increases soil organic matter which increases soil tilth, a major factor in determining whether rain will infiltrate or run-off. Next season’s crops can be planted through the crop residue. The more a field is plowed, the more organic mater is
lost, thus the potential for soil erosion and sedimentation is increased.

Barnyard System: Concrete walls around a barnyard prevent barnyard runoff from entering streams and rivers by containing the manure when it rains. Screens and a grass filter are used with the system to ensure that the barnyard waste filters properly instead of running unfiltered into streams.

Dam: An earthen dam is constructed to stabilize an area where a gulley is causing significant soil erosion. Dams hold back runoff water from storm events and trap up to 70% of the sediment that enters the structure.

Stream stabilization: Large rocks are placed along the stream bank and in the toe of
the stream to prevent banks from eroding and sloughing.

The tour also included a visit to the Grant County wetland near Hwy 61 where the group learned more about the importance of wetlands in the river system and about ways any citizen of the watershed can help improve and maintain clean waters in the Platte River watershed.

Wetlands are an important part of the watershed because they slow down the flow of surface water, reducing the severity of floods. Wetlands act like a big filter, removing sediment and contaminants form the surface water before it moves downstream into larger rivers and lakes. Wetlands also provide food and shelter for many fish and waterfowl.

Anyone in the watershed can protect streams by planting a rain garden, a low garden designed to collect rainwater during storms and slowly filter water into the ground. People who have a river or stream running through their property can leave a buffer strip of un-mown grass or plants along the stream to catch nutrients and runoff from their yards.

This wetland area of the watershed is historically significant as it was once the general location of the city of Paris, an early settlement founded by a Frenchman. Paris Township derives its name from this ghost town.

To the delight of all, multiple species of fish…and a snake…were collected from Blockhouse Creek during the fish shocking demonstration. The unique features of each of the species where demonstrated and the young Friends in the group had an opportunity to get up close and personal with our aquatic neighbors. Blockhouse Creek is known for its smallmouth bass population. Over seventeen other species of fish are known to populate this stretch of the creek.