DEPARTMENT OF CITY PLANNING

Riverbank Stability Survey & Best Practices Study

Concerned by the number of landslides happening throughout the city, Pittsburgh’s Department of City Planning partnered with the U.S. Army Corps of Engineers (USACE) Pittsburgh District to assess the conditions of riverbanks along the Allegheny, Monongahela, and Ohio Rivers. The partnership’s objectives were to assess and map the current condition of approximately 43 miles of riverbank and develop an applied best practices document to guide future remediation of unstable riverbanks.

About the Riverbank Stability Survey

The team first developed evaluation criteria based on observable characteristics of the Pittsburgh Pool’s riverbanks. Attributes included:

  • Bank material and condition,
  • Slope,
  • The presence and type of vegetation,
  • Extent of impervious surfaces within the riparian area, and
  • Presence and/or extent of existing features that could further contribute to bank instability (ex, existing erosion or undercutting, man made structures).

Once these criteria were established, the USACE spent several days sailing the rivers to visually assess the banks. The assessment was done on all banks within Pittsburgh City limits, and on some neighboring municipalities’ banks.

The USACE created an interactive map with the survey findings.

Other features included on the map are the route of the survey boat, photos of points along the riverbank, location of ALCOSAN culvert and outlet locations, bicycle trails, amount of impervious surface within 75 feet of the riverbank, and zoning categories.

 

They also created a decision tree structure to define and assign bank conditions scores to the various riverbank typologies.

Riverbank Decision TreeThe final assessment results were based on material type, material condition, slope, observed typology, and riverbank condition.

About the Riverbank Best Practices Study

Once the team had categorized riverbank typologies, the USACE used the results to organize a Best Practices Guide, designed to assist with identifying the most effective riverbank stabilization and rehabilitation techniques for each riverbank typology. The Department of City Planning, Riverlife, and the USACE Pittsburgh District compiled pertinent existing reports and studies regarding Pittsburgh riverbank and riparian ecology, and best practices for riverbank rehabilitation and stabilization for urban riverbanks.

Riverbank stabilization approaches included in the report fall within the broad categories of bioengineering, erosion and sediment control, stormwater management, and geotechnical techniques.

After a description of the recommended approaches, the utilizes a series of tables to organize recommended stabilization techniques by final riverbank condition categories.

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