C. DESCRIPTION OF HABITAT MAPPING UNITS (HMU) 



1) Aquatic 



This HMU included all the open water areas associated with the 

 rivers, major streams, ponds, lakes, sloughs and marshes located 

 within the area of concern. All the emergent vegetation zones 

 identified within or along the edges of the open water area were 

 included in the maj^ing unit. Few streams were large enough to be 

 easily identified from the aerial photos, therefore, they were not 

 included in the acreage calculations for this type. The extent of 

 this type was measured in acres, with the length of the two rivers 

 and their tributaries, including intermittent streams, also mea- 

 sured in miles of stream channel. 



2) Gravel Bars 



These were unstable areas containing sparse vegetation assoc- 

 iated with islands and streambanks. These areas were usually 

 covered with water during periods of high flows which inhibited the 

 establishment of vegetative cover. 



3) Sub-irrigated Grasslands/Meadows 



This HMU included those areas dominated by a variety of 

 grasses, sedges (Car ex s pp .) and rushes (Juncus sgp .) 

 influenced by the presence of an elevated water table readily 

 available to the root system. Agricultural hay meadows were in- 

 cluded within this type and composed the majority of the areas 

 identified as sub-irrigated grasslands. A variety of trees and/or 

 shrubs were sometimes present within this type; however, they 

 composed less than an estimated 10 percent of the total canopy 

 coverage . 



4) Deciduous Shrub Riparian 



This HMU contained a deciduous shrub overstory with an under- 

 story composed of a variety of grasses, forbs, and shrubs. Decid- 

 uous or coniferous trees were occasionally scattered throughout; 

 however, they did not comprise more than an estimated 10 percent of 

 the total overstory. 



5) Deciduous Tree Ripar ian 



This HI'4U contained an overstory (greater than 10%) composed of 

 deciduous trees, primarily black cottonwood (Populus trichocarpa) . 

 A dense shrub and herbaceous understory was usually present. Scat- 

 tered conifers were found within this HMU; however, they comprised 

 less than an estimated 20 percent of the total tree canopy. 



