Multi-Objective Stream Crossing Structures in the Garnsey Range

Project Overview

Garnsey Range is an important training asset for the Army and Fort Moore and continued access to the area is critical to the military mission. The roadway crossing at Shell Creek within Garnsey Range has historically utilized traditional corrugated metal pipes to convey flow through the channel. This solution has resulted in multiple structural failures that have led to blowouts, rendering the crossing impassable for standard range operations. These traditional solutions to stream crossing design also pose a barrier to aquatic organisms that disrupt connectivity throughout the stream’s watershed.  

We performed a preliminary analysis of this crossing and utilized an Engineering with Nature approach to develop a design of a multi-objective stream crossing structure. The goal was to provide a  robust, climate-resilient design that not only provides hydraulic capacity to safely pass flows attributed to changes in future land use and rainfall, but also supports aquatic organism passage and floodplain connectivity.  

Historical imagery of the drainage area and surrounding watersheds was analyzed to better understand the legacy of land management and anthropogenic disturbances.

Project elements

The old-fashioned culvert opening at Garnsey Range, which is less accessible for aquatic organisms and can contribute to roadway flooding.

The Problem

In-depth hydrologic and hydraulic analyses indicated that the most recent crossing solution, an 84-inch corrugated metal pipe, experienced significant roadway overtopping during the 25-year storm event. Further analysis indicated that a three-sided structure with a 20-foot span and 10-foot rise has the capacity to convey the 100-year storm event associated with an existing land use and existing rainfall pattern scenario; however, it does not have the capacity to pass flows attributed to future rainfall patterns or land use changes.

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