Stream Widtii 



Stream width is difficult to measure accurately from photos. Perhaps the most practical 

 course is to group the stream segments on photos into width classes. This method produces 

 reliable estimates. Appropriate class limits for small mountain streams are: 



1-20 feet 

 21-50 feet 

 51-100 feet 

 101-200 feet 



Limits can be established as needed, depending on conditions in the area under study. However, 

 for evaluation of recreational possibilities of streams, the above classification is generally ade- 

 quate. If estimates of stream surface area are needed, the adjusted stream length and the 

 midpoint value for the width class can be multiplied together. Length of segments may be de- 

 termined in any convenient manner, depending on the general amount of variation in stream width. 



Stream Gradient 



Gradient can be determined most easily directly from contour maps. If contour maps are 

 not available, elevation differences may be determined by parallax wedge measurements on 

 aerial photos. Once the adjusted length for the entire stream has been determined, the gradient, 

 in percent, can be found by dividing the elevation difference between two points by the adjusted 

 stream length between these points and multiplying the result by 100. 



Streambank Cover 



Streambank cover can be recognized by an experienced photo interpreter and can be 

 classified for stream segments as: 



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



2. Brush- -woody vegetation up to 20 feet in height. 



3. Open --no shrub or tree cover recognizable on photos. 



If vegetation cover maps have been prepared for other purposes, they may provide ade- 

 quate cover information without further photo work. 



LEVELS OF INTENSITY OF AN INVENTORY 



The procedures in a water resource inventory may be combined in several ways to make 

 up inventories of varying degrees of intensity. 



LAKE INVENTORY 



In the early planning stage of the inventory, some decision will probably be made as to 

 the amount of information desired; however, in the course of the study, it may become advis- 

 able to step up or step down in intensity. Particularly promising lake areas discovered in the 

 course of a low-intensity study may warrant closer examination and measurement. In a high- 

 intensity study, a group of lakes of similar nature may require only sampling. 



As a guide in the choice of level, information is needed on the time required for each 

 procedure. In the present study the following evaluation has been made: 



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