sediment input to the lake or because the shores are moderately steep. These 

 shores are stable and are affected little by changes in water levels. 



Beaches and spits of sand or mixed sand and gravel occur along lake shores in 

 which the shore substrate consists of glaciof luvial sands and gravels. These 

 features commonly occur on the eastern shores of lakes, as prevailing south- 

 westerly winds create waves of sufficient magnitude to erode shoreline banks 

 and transport material along the beach. 



Mud flats (vegetated and unvegetated) may occur along lake shorelines, but are 

 found infrequently, except where lake levels are lowered artificially. 

 Littoral flats may occur lakeward of beach and spit shorelines or may occur 

 unassociated with such features in sheltered shallow coves of lakes with high 

 mud-content sediment input. Littoral flats also may be associated with deltas 

 that form at the mouths of streams entering a lake. 



A more common depositional feature of coastal Maine lakes is delta deposits at 

 the heads of lakes. While generally of small areal extent (10s of hectares) 

 they indicate the first step of lake infilling by sediments delivered in 

 streams. They are usually sand deposits that are capped by mud sediments and 

 are deposited after spring freshets or during winter months. Delta surfaces 

 usually are vegetated with freshwater aquatic vegetation and upland emergent 

 plant species. The deposits are irregular in shape and often have a straight 

 channel in the center, leading from the stream to the open lacustrine tract. 

 The distal (outer) margins of the delta may be rimmed by sandy beaches and 

 spits. Beaches and spits are common where sediment-input sand volume is high. 



Deltas extend into the lake depths by deposition of sand on the prodelta face 

 below the delta channel mouth (progradation) . Sand deposited in this way 

 (extending laterally into the lake) forms three types of beds (bottomset, 

 foreset, and topset beds). Mud accumulates on the surface of the delta, 

 entrained by aquatic and emergent plants during high spring runoff and flood 

 water levels. Thus, delta surfaces are built up over time. No studies have 

 be_n undertaken to ascertain delta progradation or accretion (vertical growth) 

 rates. Present rates of lake infilling or lake delta progradation within the 

 characterization area are unknown but it can be assumed that these rates are 

 highly variable. 



The areal extent and processes of littoral deposit are determined by the rate 

 of sediment input, by lake water levels, and by waves. Lake levels fluctuate 

 due to watershed runoff input or as a result of manipulation by people. 

 Unless there is a rapid input of sediment from alongshore, a raising or 

 lowering of the water level by more than several tens of centimeters either 

 will cover existing littoral deposits or leave them stranded subaerially, 

 respectively. In the latter case, these deposit surfaces will become 

 colonized by upland plant vegetation. 



Soils 



The primary influence that the geology and soils of the coastal zone have on 

 lake ecosystems derives from their effect on the chemistry of runoff waters 

 from watersheds. If rock chemistry is such that high concentrations of 

 nutrients are released into the runoff waters the effect will be an increase 

 in biological productivity. The structure, depth, and permeability of the 



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