64,968 tons of sediment are delivered annually to the nearshore area northeast 

 of Casco Bay. Total organic carbon discharges as particulate matter range 

 from about 5 mg/1 to 12 mg/1 and do not appear to vary seasonally (U.S. 

 Geological Survey 1976). Schnitker (1974) reported that under normal 

 meteorological conditions suspended sediment concentrations entering estuaries 

 from the ocean are about 2 to 2.5 mg/1. During storm periods, this 

 concentration increases to 6 mg/1. Schnitker 's (1972) studies in Montsweag 

 Bay, the Sheepscot River estuary, indicate that sediments derived from within 

 the basin normally reach concentrations of about 6 mg/1. If the normal 

 discharge concentrations (about 1 mg/1) entering the estuary from rivers are 

 subtracted, it becomes evident that about 5 mg/1 of concentrate is derived 

 from within the basin. This sediment remains within the nearshore area as 

 redeposited material. Suspended sediment concentrations of bottom waters 

 within the estuary may exceed 10 mg/1 during and immediately after storm 

 periods. Schnitker (1972) reported that these values of sediment flux 

 resulted in a net deposition rate of 0.7 to 1.1 inch (1.9 to 2.8 cm) per year 

 in Montsweag Bay. These figures probably are applicable to most of the 

 intertidal nearshore area. The nearshore sedimentation of fine-grained 

 sediments, coupled with an ongoing sea level rise of approximately 0.08 to 

 0.14 inch (0.22 to 0.36 cm) per year (Hicks 1972) results in a sediment wedge 

 accumulating at the nearshore, which will migrate landward (figure 2-21). 



Shoreline erosion . Shoreline erosion along the Maine coast has been 

 documented by Timson and Kale (1977). Erosion of unconsolidated shorelines is 

 dependent on several factors including: the amount of wave energy impacting 

 the shoreline, the type of unconsolidated sediment existing at the shoreline, 

 shoreline orientation, and the influence of people. Natural erosion of 

 unconsolidated shorelines is occurring at a rate of about 0.5 to 2 feet (15 to 

 61 cm) per year along the coast. Many beaches are eroding at greater rates, 

 primarily due to the influence of protective engineering structures and 

 navigation works. The highest rate of shoreline erosion occurs at Hunnewell 

 Beach, Phippsburg, at the mouth of the Kennebec River. Timson (1977) 

 attributes this high erosion rate to dredging in the Kennebec River estuary 

 between the river mouth and the city of Bath. 



Acceleration of erosion rates, to recession rates of up to 90 feet (27 m) per 

 year, is caused by disruption of normal sand transport pathways by the removal 

 of channel bar sediment from the estuary floor. Offshore disposal or disposal 

 of sediment elsewhere within the estuarine system has disrupted the rate of 

 delivery of sediment to the Popham Beach area. Supporting evidence for this 

 disruption includes: 



1. Hunnewell Beach was progradational until 1940. Dredging of the 

 Kennebec began in 1942 and recurred at intervals of 2 to 4 years. 

 Hunnewell Beach became recessional with the commencement of dredging. 



2. The volume of sand lost from Hunnewell Beach from 1940 to 1974 

 approximates the amount of material dredged from the estuary during 

 the same time interval. 



2-42 



