problems in the loose soils characteristic of the Lake States area which require 

 3ontinual and expensive attention. These problems can be alleviated to a great 

 extent by constructing such weirs diagonally across the stream or in a "V" plan. 

 The increased area for passing water thus produced decreases the impounding action 

 of the weir to a minimumjscouring and erosion are likewise brought to a minimum. 



(2) and (3) Portable- type weirs and traps of the Carp Creek and Milligan 



Creek styles for medium-and small-size streams respectively, for cap- 

 turing spawning runs (Figs. 3-5, Ik and 15). 



Carp Creek style portable weirs and traps can be installed 

 and operated effectively in streams up to 00 feet wide if maximum 

 flood levels passing through the screens do not exceed 30 inches in 

 depth, and if careful maintenance is accorded the weirs during flood 

 periods. The maximum volume of flow which these weirs can probably 

 handle is about 300 cubic feet per second. Where greater volumes 

 of water must be passed, permanent-type structures are recommended. 



These weirs, constructed of lumber, l/2-inch-mesh hardware 

 cloth and steel fence posts, are perhaps the most economical control 

 device which has been developed to date (Figs, llj and 15). They may 

 be prefabricated and installed for a unit cost of $26.00 per linear 

 foot of stream width exclusive of engineering and construction- 

 supervision costs. This unit cost is based on a "V'-plan structure 

 with the wings of the weir set at a 32° angle to the bank. The term 

 "portable" weir is derived from the fact that after each spawning run 

 season, all of the structure except the sills, up-right posts, and 

 abutments is removed from the stream and stored until the next season, 



Where experience gained from one or more years of operation has 

 shown that a portable-type weir can be operated effectively in a given 

 stream, an inexpensive weir substructure and abutments of concrete 

 can be installed. Portable-type weirs can be reinstalled repeatedly 

 and operated with increased ease and with maximum effectiveness for 

 many years upon such a stable base. 



The Carp Creek stye is impractical in most streams less than 10 

 feet wide. The Milligan Creek style weir was developed for these 

 smaller tributaries, 10 feet or less in width, in which maximum flood 

 levels passing through the screens do not exceed 2li inches (Figs. 3 

 and 15). 



Uo 



