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Abstract: Session F  3:30 pm (Back to Session F)
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Consequences of Localized Q500+ Storm Events on Newly Installed and Mature Stream Restorations

Steven F. Church
KCI Technologies, Inc.
Richmond, VA

Authors:  Steven F. Church, Kathy L. Hoverman

Pride sweeps over a stream restoration designer when the landscaping contractor mulches the last tree installed on a restoration site he/she designed and the project is considered complete. Following the completion milestone, the designer and client then contemplate if the restoration will remain structurally sound and stable during future rainfall events. What if those rainfall events far surpass bankfull or even the 10- or 100-year Q and enter the realm of 500-year and greater exceedance probabilities?

Watersheds near Ellicott City (in Howard County), Maryland have endured two rainfall events since 2016 that have surpassed the 500 year exceedance probability (July 2016 and May 2018). Stream restoration projects within those watersheds transported those event flows. Several stream restoration sites designed by KCI Technologies for Howard County were visually assessed immediately after the May 27, 2018 flood event. Some of the restorations were so new at the time that very little vegetation was established, while other sites were several years old and had well-established vegetation.

What impacts did that extreme rainfall event have on those restorations? Did the bed materials and bank structures remain in place? Did the riparian vegetation withstand the floodplain inundation? What failed and how did it fail? This presentation will summarize the findings of the visual assessments completed by KCI stream restoration staff.