Michigan DOT I-696 Slope Restoration Project

The Michigan Department of Transportation (MDOT) restored roadside slopes along approximately 9 miles of I-696 between I-75 and I-94 using alternative plants that are heat and drought resistant and will help stabilize the slopes to prevent erosion.  The slope restoration project is part of an effort to reduce stormwater runoff from roadways and thereby protect the quality of Michigan waterways.  The 55,000 plants, shrubs, and trees selected create a variable-depth root structure to help stabilize the steep slopes and reduce runoff volume and velocity, particularly during intense rain events that are projected to increase in intensity and variability with climate change.

Michigan is projected to experience more frequent and intense rainfall events as well as longer periods of higher summer temperatures because of climate change.  Roadside slopes may be at higher risk of erosion due to more intense rainfall and vegetation loss due to extreme heat.  MDOT designed this alternative landscaping project for the steep slopes along a portion of I-696 in order to reduce the likelihood of both erosion and vegetation loss. 

Traditionally, steep slopes along Michigan’s roadways have been seeded with different turf grass species.  The grasses must be mowed regularly, which creates ruts in the soil.  During intense rain events, the ruts are further washed out and the shallow and invariable root structure of turf grasses cannot adequately absorb the high-velocity water flowing down the slopes.  As a result, sediment erodes from the slopes and is carried over roadways by the stormwater, leading to pollution of rivers and lakes. 

MDOT selected a variety of plant, tree, shrub, and vine species that would both resist extreme heat and drought and create a deeper and more variable root system to help stabilize the slope and absorb more stormwater during heavy rainfall.  The alternative landscaping project is expected to reduce erosion and resulting sediment pollution of waterways, while also reducing strain on storm sewer infrastructure.  MDOT also installed a barrier wall to allow the slope to be flattened slightly and a swale to catch additional rainfall not absorbed by the root structure, reducing the likelihood of stormwater spilling over onto the roadway.

In addition to benefiting the environment, the slope restoration project will help protect motorists, through installation of a barrier wall.  It will also reduce hazards to state employees, by removing the need for risky mowing on steep slopes.  The project utilized 55,000 plants and was funded by $9 million from the American Recovery and Reinvestment Act to bring economic relief to the Detroit metropolitan area.  The plants were selected based on research indicating species most able to withstand the Michigan climate and a variety of adverse roadside conditions. 

 

This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on February 17, 2015.
 

Publication Date: Fall 2012

Author or Affiliated User:

  • Michigan Department of Transportation

Related Organizations:

  • Michigan Department of Transportation

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  • Best practice
  • Case study

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