Herring River Restoration Project – Low-lying Roadways Review and Discussion

Ball, D.

ENSR completed a review of low-lying (or “low-laying”) roadways (LLRs) to determine what roads would be adversely affected by the modification of tidal control at Chequesset Neck Road. Planned modifications to tidal control at the existing restriction would result in a gradual increase in the range and elevation of daily tidal flooding in the Herring River floodplain. Under current project planning, the limit of tidal inundation upstream of Chequesset Neck Road will be restricted by the modified tidal control to elevation 5.1 feet (NAVD 88, or 6.0 feet NGVD 29). The various alternatives being considered for implementing tidal restoration are described in a separate report (DMJM-Harris and ENSR, June 2007). If full (i.e., unrestricted) tidal exchange returns to the Herring River floodplain, tidal elevations will more closely match those occurring in Wellfleet Harbor. Accordingly, ENSR’s evaluation in this report has used the tide heights that occur in Wellfleet Harbor to classify the full potential of roadway flooding above Chequesset Neck Road. There are a number of roadways upstream of the existing tide gate considered LLRs due to the elevations of their paved or unpaved road surfaces. The 100-year flood elevation in Wellfleet Harbor is 9.44 feet (10.3 ft NGVD 29), and therefore low-lying roadways at or below this elevation have been considered in this assessment. However, it is stressed that tidal controls are proposed to be implemented to protect low-lying properties from tidal flooding while also promoting ecological restoration of the River and its bordering salt marshes.

Herring River Restoration Project – Low-lying Roadways Review and Discussion

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