Nelson Slough - East Park WMA
Upon completion of the Nelson Slough project, wildlife managers will be able to more effectively manage flood waters to reduce "bounce", thereby improving habitat conditions for nesting and migrating waterfowl and other wetland wildlife on this nearly 2,482-acre impoundment. This goal will be achieved through
1) replacement of the existing outdated water control structure which also doesn't have the needed conveyance capacity; and
2) increase embankment heights by three and a half feet to provide more freeboard during large flood events, thus improving management capacity and overall safety of the project to meet the current Dam Safety Codes.
What is the issue:
Nelson Slough is an on-channel impoundment on Judicial Ditch 19 (JD19) built in 1971. In its over 50-year lifespan, the project has provided wetland wildlife habitat benefits and flood damage reduction benefits on East Park Wildlife Management Area (WMA). However, flood waters come more frequently than anticipated, and slow release of those flood waters is impeding wildlife production on the WMA. The structure has also passed its expected life span and doesn't meet the design standards of today.
What is the solution:
A project team established according to the 1998 Red River Basin Mediation Agreement to discuss how the project could best fit current needs. The Project Team consists of representatives from the Middle Snake Tamarac Rivers Watershed District (MSTRWD), the Minnesota Department of Natural Resources (DNR), and other local stakeholders, and settled upon the proposed design. The Watershed District along with the DNR is now looking forward to construction.
The project has two primary purposes:
1.Improve wetland wildlife habitat within the impoundment. Wildlife habitat, in particular for migratory waterfowl and wetland birds, will be managed to provide both forage and resting areas during the migration seasons, but also nesting habitat for those over-water nesting birds.
2.Improve the water storage capacity of the impoundment. In the new design the impounding capacity is not expected to change, but rather timing is expected to be utilized more effectively so the flood damages downstream are expected to be reduced with the improvements to the project.
Design and Scope of work:
MSTRWD-DNR partnership is proposing to replace the existing water control structure with a structure more capable of handling current flood events that feature the below changes:
The existing 6' primary and 70' secondary spillway will be changed to overall 250' spillway, with a 40' primary and 30' of secondary spillway, providing additional capacity that the existing structure lacks to manage the water elevation.
In addition, the existing embankments will be raised approximately 3.5' above the existing embankments to provide additional freeboard for expected flood events and to meet todays' design standards.
Managers will be able to manage water elevation and release timing more effectively with the completion of this project. Currently flood waters are slow to leave the impoundment, flooding out water bird nesting attempts and negating potential storage for follow-up flood events. Furthermore, the current embankments leave little freeboard, limiting the volume of flood waters that may be stored during any one event. With the replacement of the water control structure, the improved embankments, and improvements to correct stability issues downstream on JD 19, flood waters can be effectively stored and metered out following downstream flood peaks to decrease damages caused to infrastructure and adjacent farmlands.
Through improvements to the JD 19 system to improve stability, proposers of the project also expect to see improvements in water quality downstream in the legal ditch system as well as in the Tamarac River and Red River.
$4,174,000 the second year is to the commissioner of natural resources for an agreement with the Middle-Snake-Tamarac Rivers Watershed District to restore and enhance wetland and upland wildlife habitat on Nelson Slough and East Park Wildlife Management Area in Marshall County, Minnesota.
Improved aquatic habitat vegetation - Pre-project submerged aquatic plant conditions have been documented on Nelson Slough by the Shallow Lakes Program of the DNR. We anticipate these surveys to continue. With this data, managers will be able to compare post-project conditions to those from past years to better guide management into the future.
Remote data loggers have been documenting water levels continuously throughout the open-water season for multiple years at Nelson Slough. Since prolonged high water can negatively affect submerged aquatic vegetation (SAV), managers will be able to estimate how the impacts to SAV would have differed without the completion of the project
MSTRWD and DNR, MSTRWD and RRWMB, RRWMB and MSTRWD and BWSR