2 Background 



Lake Huron is the fifth largest inland body of water in the world and second 

 largest in North America with a surface area of 59.600 sq km (23,010 square 

 miles). Its maximum depth is 229 m (750 ft), and it drains an area of approxi- 

 mately 129,500 sq km (50,000 square miles) (Hough 1958). Except for a small 

 amount of water diverted from Lake Michigan at Chicago into the Illinois River, 

 the entire upper Great Lakes system (Lake Superior, Lake Michigan, and 

 Lake Huron) discharges through Lake Huron and into the St. Clair River, 

 Lake St. Clair, the Detroit River, and Lake Erie. Lake Michigan and Lake Huron 

 are connected by the Straits of Mackinac and have the same water level. The 

 surface of Lake Superior is approximately 6.1 m (20 ft) higher than that of 

 Lakes Michigan and Huron and is connected to Lake Huron by the St. Marys 

 River, which contains a series of locks and canals (Hough 1958). 



The Great Lakes do not experience astronomical tides, but water-level fluctua- 

 tions are common as a result of storms, wind, and barometric pressure differences. 

 Fluctuations in the still-water level result from seasonal precipitation patterns and 

 snowmelt runoffs and over longer time periods in response to large-scale weather 

 patterns. In general, the Great Lakes water levels are highest in the spring and 

 summer and lowest in the winter. Figure 4 shows historic water levels of 

 Lake Huron. Because the Great Lakes are composed of fresh water, ice is 

 common throughout the system. Shore ice can extend up to 2 km ( 1 .2 miles) 

 offshore, and on occasion ice can cover an entire lake. Mobile ice fields and ice 

 flows can cause damage to coastal structures. 



The study site at Port Huron, Michigan, is located on the western shore of 

 Lake Huron just as the lake narrows into the St. Clair River. This transition 

 region is highly dynamic with strong river currents (depth-averaged velocities in 

 excess of 1 .8 m/sec (6 ft/sec) just north of the Blue Water Bridge and 0.9 to 

 1 .2 m/sec (4 to 5 ft/sec) in the vicinity of the boat basin). 



Two shoaling studies have been conducted for the boat basin at Port Huron. 

 The USCG Academy conducted the first study in 1974 (USCG Academy 1974). 

 A subsequent study was conducted by the USCG Civil Engineering Unit, 

 Cleveland (CEU Cleveland), in 1991 (CEU Cleveland 1991). These reports are 

 summarized below: 



Chapter 2 Background 



