Mitigation of Harbor Caused Shore Erosion with Beach Nourishment Delayed Mitigation, St. Joseph Harbor, MI

by Charles N. Johnson, U S Army Corps of Engineers, Chicago, United States,



Document Type: Proceeding Paper

Part of: Coastal Engineering Practice

Abstract:

St. Joseph Harbor MI. was the first Corps of Engineers Section 111 erosion-mitigation project to be built. Between 1 Jun 76 and 5 Aug 85, about 1,067,000 cy of fine sand was placed in the feeder beach area about 3500 feet downdrift of the harbor. Between 13 Jan 86 and 20 Nov 87, about 181,400 cy of gravel and coarse sand, 2-4 mm dia., was placed instead of fine sand. Between 31 May 88 and 1 Jun 91, 231,800 cy of fine sand was placed. The fine sand has not stayed at the water's edge as it has been carried downdrift past the many seawalls within the first 4 miles downdrift, but may have come ashore along a 1.5 mile unprotected stretch at Glenlord Road farther south. The gravel consumes itself building beaches over every seawall it encounters, hence moves very slowly downdrift. This qualitative difference in sand vs gravel movement appears to have created a depletion transient following the 1983-84 fine-sand nourishments. Adverse effects of the harbor may now be the cause of severe erosion spreading to more than 8 miles downdrift from the harbor.

Subject Headings: Sandy soils | Ports and harbors | Gravels | Erosion | Coastal management | Beach protection and nourishment | Sand (hydraulic)

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