The municipality of Derry Township encompasses the borough of Hershey, Pa., where historical flooding and erosion problems have plagued the area.
Derry Township contracted Herbert, Rowland & Grubic Inc. to design a comprehensive upgrade to the township’s integrated storm water management plan. A major contributor to the flooding along Cocoa Avenue was the overflow of a minimally sloped (less than 0.1%) Spring Creek tributary with a 1.54-sq-mile drainage area that had incised a new channel with 90-degree bends. The $5.36-million project included the relocation of the tributary back to its historical location on the Hershey Trust property and was constructed by N. Abbonizio Contractors. The realigned tributary, with an increased conveyance capacity, was constructed to provide ample floodplain relief that would minimize overtopping of the tributary onto Cocoa Avenue. The stream channel was constructed in the fall, and the banks of the realigned stream channel were lined with domestically manufactured East Coast Erosion Control 12-in.-diameter coir logs. Jamie Higgins Landscaping placed dormant live willow and dogwood stakes in the stream bank upslope of the staked-in-place coir logs to establish a riparian zone. When properly prepared, handled and placed, the live stakes root, grow and form a stabilizing root mat that reinforces the soil as it binds soil particles and provides a medium for the plants to create a shaded canopy over the stream.
The coir logs protected the banks from the energy exerted by ice throughout the winter, then minimized accelerated erosion and the resulting sedimentation during the ensuing spring growing season. With the commencement of the growing season, the live stakes sprouted stems with leaves and various grass species were observed growing within the coir logs.
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