Clarity of Lake Water 



The relative clarity of the water contained in lakes can be judged on the basis of the color 

 tone of the photo image. Lakes which appear light gray or white (opaque) on panchromatic photos 

 generally contain suspended solids. It is more difficult to predict the water clarity of a lake 

 which appears dark on the photo. The water may be clear or may contain varying amounts of 

 suspended material . 



Shore Cover 



The type of vegetation surrounding a lake influences its recreational utility. Wood for 

 campfires is difficult to obtain at lakes without tree cover. Dense brush cover may require 

 construction of trails. Boggy or marshy areas surrounding a lake make access difficult. For 

 these and other reasons, it is desirable to indicate the approximate percentage of the lakeshore 

 that falls in the following cover classes: 



1. Fore St --stands of trees averaging 20 feet or more in height. 



2. Brush- -woody vegetation less than 20 feet in height. 



3. Bog --wet areas of grasses and sedges that usually appear in dark tones on photos. 



4. Meadow- -areas of grasses and sedges that are drier than bog and usually appear in 

 lighter tones on photos. 



5. Barren --no vegetation present. 



INVENTORY OF STREAMS 



Aerial photographs provide far less information for streams than for lakes. Streams less 

 than 20 feet wide can be easily obscured by tree or brush cover, so that any measurement is 

 difficult. Depth measurements such as those made on lakes are impossible, even when the 

 stream is plainly visible. Nonwater features are often mistaken for streams on photos. Live 

 streams that are not hidden by overtopping vegetation appear as thin and meandering dark lines 

 (fig. 4). Shadows of steep drainage banks, as well as the outcrops of dark rock strata, can 

 appear as similar lines. 



In spite of these problems, photo interpretation and measurement can be used to obtain 

 estimates of stream length, width, and gradient, and a general description of streambank cover. 

 The principal value of the photos in a stream inventory is to correct and supplement the informa- 

 tion given on available maps of the area. In addition, photos are a logical tool for field location 

 of sample points if on -the -ground measurement of additional stream characteristics is planned. 



If no field measurements are to be taken, aerial photos should be used to improve the 

 basic description of streams given on the best maps of the area. Most modern maps are made 

 from aerial photos and show the location of streams fairly accurately. However, because in 

 general these maps are based on small-scale photos, much detail visible on 1:20,000 scale 

 photos is not apparent to the mapmakers. 



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