Recent erosion and slumping events on the Songo River have caused
trees and shrubs to collapse into the river channel. The above photo shows
how erosion has caused entire sections of vegetation to become undermined
and slide into the river.
6. Analysis of impacts of lake-level management on the Songo and
Crooked Rivers.
FOSL has observed an unnatural degree of erosion and recession of the banks
of the Songo and Crooked River. Because of the dynamics of water moving
through a meandering river delta one might expect some degree of erosion
and movement of the river course over time. The rate of erosion and undercutting
of embankments now occurring appears to be larger that what would be expected
naturally.
FOSL suspects boat traffic with higher and more stable water levels in the
summer month is exacerbating the erosion and recession. The level of Sebago
Lake influences much of the lower reaches of the Crooked River and all of
the Songo River below Songo Locks. Eroded embankments above the Crooked
River bridge at Songo Locks appear to have a high clay content. FOSL requests
the EIS analyze the degree of erosion and recession now occurring on the
Songo and Crooked Rivers. This analysis should include the recession rate
of the embankments, impact of eroding silts and clay turbidity in the river,
delta habitat and the lake ecosystem.
See U.S. Army Corps of Engineers' CREEL Monograph 85-1, p.3, paragraph 3
and 4, which states:
"The introduction of sediment into the adjacent water column has significant
ramifications, perhaps the most important of which are the sediments' effect
upon water quality and biological activity .... Suspended sediments affect
aquatic biota through their lowering of light penetration (turbidity) and
the resultant changes in photosynthesis and primary bilogical production
and species composition. (Stall 1972, Oschwald 1972, Hecky et al. 1974,
Geen 1974, Barko 1981)."
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