Lansing Big Lake: A Backwater and Side Channel Restoration Case Study

In the Upper Mississippi River floodplain, many backwater habitats
are significantly impacted by increasing connection with the main channel,
increasing sedimentation, and loss of topographical diversity. In 1995, the
Upper Mississippi River Restoration - Environmental Management Program
initiated a project that employed several different management measures to
reduce hydrological connectivity between the main channel and the Lansing Big
Lake backwater complex. Lansing Big Lake is a 1,500 acre backwater fed by six
secondary channels, located in Pool 9 near Lansing, IA. The total habitat
complex, including floodplain forest, secondary channels, backwater lakes,
and islands encompasses over 9,000 acres. In the 1980s and 1990s, many of the
secondary channels connecting Lansing Big Lake to the main channel had been
eroding progressively larger, conveying around 25% of the total river
discharge through the backwater system. The increased flow was depositing
large quantities of sediment, filling in the deep water habitat of the
backwater. Higher flow velocities were also creating unsuitably cold
overwintering conditions. The original goal of the project was to reduce flow
through the backwater, restoring overwintering habitat for centrarchids.
Seventeen years later, evaluation of these management measures has provided
lessons regarding their long-term effectiveness and the response of the
backwater habitat.  Several different measures were used to reduce erosion
and flow through secondary channels; some were more successful than others at
maintaining target discharge conditions. This project offers lessons
regarding management measures, objective-setting, and environmental response
to backwater restoration. The project also provides an opportunity to examine
the evolution of restoration planning over the course of EMP, including the
new context provided by recent large scale planning efforts to establish
system and pool-scale objectives.