than a stream with comparable mean flow but a less variable flow (Beaumont 

 1975). Unregulated streams that have irregular flow patterns are more likely 

 to cause flood damage and erosion than those with regular flow patterns. 

 Variations in flow may influence animal behavior. Upstream migrations of fish 

 such as Atlantic salmon, an important Maine sport fish, are cued by peak 

 flows. Along the Maine coast, as in most of New England, maximum flows occur 

 in early spring (coinciding with snow melt) and minimum flows in late summer 

 and early autumn (Langbein and Wells 1955). 



Pollutant transport . In addition to temperature and precipitation, 

 transportation of pollutants, particularly nutrients, acids, and heavy metals, 

 has important effects on streams. Acid precipitation and associated heavy 

 metal contamination are of particular concern in Maine (Davis et al. 1978; and 

 Norton et al. 1978), where most natural waters have a low buffering capacity 

 (i.e., low resistance to changes in acidity). Under conditions of extremely 

 low buffering capacity (more likely to be encountered in lakes than in rivers) 

 acidification and metal contamination may interfere with fish reproduction 

 (Beamish 1976). Airborne acids and metals are usually the result of fuel 

 combustion, while nutrients are normally dust particles raised by wind, 

 farming, building construction, and similar dust-producing activities. The 

 extent of atmospheric pollutant problems in rivers of coastal Maine is not 

 known, but the general problems of acid precipitation are discussed in chapter 

 3, "Human Impacts on Coastal Maine." 



Geology-Hydrology 



The riverine system in coastal Maine lowlands originated after the Wisconsinan 

 deglaciation of about 11,000 to 13,000 years ago (Stuiver and Borns 1975). 

 Most streams are dependent upon or controlled by the geologic structure of 

 their channels or by the form and slope of the channels' surface. The channel 

 courses developed in the glacially-created terrain in response to sea-level 

 withdrawal and post-glacial upland uplift (Sayles 1938). 



Three stream course types based upon origin are present in the 

 characterization area: 



1. Large streams conforming to pre-Wisconsinan channels; 



2. Smaller streams following late glaciation meltwater stream courses; 



3. Smaller streams developing independent courses on the uplifted 

 coastal upland. 



The first type includes the tidal and lower perennial portions of the major 

 rivers (Kennebec, Androscoggin, Penobscot, and St. Croix), although portions 

 of these rivers were diverted from their pre-Wisconsinan channels by 

 glaciation (Gerber 1979). 



The second type includes many streams in regions 5 and 6 that developed on the 

 low topography of coastal lowlands. Here, water flows in a southeasterly 

 direction, parallel to the flow of glacial ice and meltwater streams. Water 

 courses are interrupted frequently by lacustrine and palustrine systems and 

 are diverted locally by marginal ridges that block their direct flow to the 

 ocean. 



6-12 



