In the summer of 1999, the U.S. Army Corps of Engineers, Philadelphia District, designed and constructed a flood protection project for Molly Ann’s Brook, located mainly in Paterson and Haledon, N.J. The brook is a tributary to the Passaic River, which flows through an urban area in New York Harbor. Communities along the 2.5-mile stretch of the brook have been subject to repetitive flooding as a result of inadequate channel capacity.
Within this location, there was also limited right of way, undulating and outcropping bedrock, and high stream velocities due to storm-water runoff from the surrounding developed areas. Erosion protection is paramount when designing flood protection projects in any environment, but it’s even more critical in an urban setting, due to limited space and the proximity of structures.
In addition to these challenges, the design of the Molly Ann’s Brook project varied from a trapezoidal riprap section to a rectangular section formed by precast concrete walls. Conventional solutions such as riprap, wire mesh gabions, cabled concrete mats, and more than 3,000 linear feet of precast concrete retaining walls were used to protect the banks of the brook and contain floods on adjacent areas.