Waterworks revetment to the south is partially protected by deteriorated groins. 

 The feeder beach for the nourishment program extends from Park St. (located 

 about 600 m south of the south jetty) to just south of the Waterworks revet- 

 ment. Beginning with the Waterworks revetment and extending about 3.5 km 

 to the south, the shore is protected by an armor stone revetment (constructed 

 for the Chesapeake and Ohio Railroad over the first 1 .5 km and for the high- 

 way by the Michigan Department of Transportation, (MDOT), for the next 

 2 km). In some places, the revetment is fronted by groins, many of which are 

 in disrepair. The final 3.3 km of shore south of the end of the revetment 

 consists of various forms of deteriorated wall structures and entirely 

 unprotected sections. 



A Section 1 1 1 mitigation plan was implemented downdrift of St. Joseph 

 Harbor in 1976 by the U.S. Army Corps of Engineers (US ACE) to address the 

 erosion problems that may be associated with the interception of sediment on 

 the updrift side of the structures. The harbor jetties were constructed origi- 

 nally in 1903 and have been estimated to trap approximately 84,000 m of 

 sediment per year (USACE 1973). The mitigation consisted of placing fine 

 sand from the harbor maintenance dredging on the downdrift beaches (Johnson 

 1992). More than 1,700,000 m of sand has been placed on the beaches of 

 St. Joseph. Table 1 provides the annual placement details for beach nourish- 

 ment between 1970 and 1995. Parson (1992) has indicated that the fine sand 

 has been a less-than-ideal material for nourishment, noting its short retention 

 time and the fact that the fine sand does not fulfill the role of the coarser 

 sediment which forms a large part of the natural beach closer to shore (i.e., in 

 the surf and swash zones). 



Coarse material was placed on the beach in 1986, 1987, 1988, 1991, 1993 

 and, most recently, in the fall of 1995 (see Table 1). This coarse sediment 

 came from upland sources and was trucked to the site. The coarse grain sedi- 

 ment has a djQ of about 2 mm and is well-sorted with a range of grain sizes 

 from 0. 1 mm to 32 mm. This material has a longer retention time and it has 

 been postulated that it may protect the underlying glacial till from erosion in 

 the critical nearshore zone (Parson 1992). 



The beach nourishment is placed between the ordinary high water mark 

 (OHWM) (177.2 m International Great Lakes Datum (IGLD), 1985) and the 

 most landward 1.2-m depth contour (174.8 m). The maximum design height 

 for the placed material is 178.3 m and its maximum width is 46 m. The typi- 

 cal beach nourishment volume is about 50 m /m over the 1-km-long feeder 

 beach or about 50,000 m in total with fine sediment applied in the spring and 

 coarse sediment in the fall. 



To classify nourishment volumes and include the results in the descriptive 

 model, annual beach nourishments were grouped into three time periods: 1970 

 to 1975, 1976 to 1991, and 1991 to 1995, for both fine (dredged) and coarse 

 (trucked) sand (see Figure 2). Prior to the implementation of the Section 1 1 1 

 plan in 1976, annual nourishment volumes averaged 23,000 m and there was 

 no trucking from inland borrow sites. From 1976 to 1991, average annual 



Chapter 2 Background 



