4 



INTRODUCTION 



Expanding urbanization and its effects of unfavorably reshaping the 

 channels of urban streams is a serious fisheries problem that has long 

 seemed obvious to biologists but may not be as apparent to others. Urban 

 stream alterations typically regarded as detrimental to fish habitat 

 include channel straightening and other unnatural relocation; excessive 

 stream widening or channel constriction through landfill, bridges and 

 culverts; impoundments; elimination of pools, riffles and biologically 

 productive side channels; removal of instream cover used by fish; and 

 construction of unnatural structures such as bulkheads, walls and certain 

 kinds of deflectors in and along streams. This situation has not been 

 thoroughly studied in quantitative terms, in large part perhaps because 

 it has seemed so blatantly obvious to specialists. Yet, when it comes 

 to making policy decisions on urban development along streams, quantitative 

 data are needed. 



Determining components of fish habitat that are adversely affected by 

 practices similar to these, although not necessarily classifiable as urban, 

 has been addressed in several studied. Whitney and Bailey (1959) and Elser 

 (1967) both found that channel alterations involved in highway construction 

 caused significant decrease in the salmonid carrying capacity of two Montana 

 streams. In particular, Elser determined the amount of cover per unit area 

 of stream to be substantially less and the occurrence of areas with more 

 shallow, fast reaches greater in altered stream sections. In a stream- 

 straightening project in Rocky Creek, Gallatin County, Montana, changes 

 in channel morphometry and loss of in-streara and bank cover were responsible 



