WSP11194 - Laserfiche WebLink

Home Browse Search

Strata 8 Cluster 3 (rm 94.0) Seven cross sections were surveyed in this sequence. The control was located on a bedrock shelf and the flow measured in the field was 329 cfs (Appendix 2, Table 10). Total length surveyed in this cluster was 2,904 ft. A short riffle separated a shallow run in the lower half and a deep run in the upper half of this cluster. At flows less than 80 cfs, the dominant habitat type was the shallow pool. Usable pool habitats were very rare in this cluster at all flows modeled. Deep run habitat did not become common until a flow of 329 cfs (24%), and was very rare at flows under 80 cfs (Appendix 2, Table 5). Cluster 6 (rm 115.5) Six cross sections were surveyed in this cluster, representing 2,184 ft of river. Flow averaged 332 cfs for these cross sections (Appendix 2, Table 11). At 332 cfs, 87% of the area was unusable, cither shallow or fast (Appendix 2, Table 6). The river in this cluster was mostly shallow riffles (Fast) and fast-shallow runs. A long, deep run was located upstream of cross section 4. a riffle that indicated the upper terminus of the sequence. However, since there were no deep habitats between cross sections I and 4, the station was extended upstream into the deep run. A cross section was placed at the lower part of the run (cross section 5) and another near the middle part of the run (cross section 6). Neariy all the usable habitat in this cluster over the modeled range of flows was ~ssociated with cross section 6. Combined clusters in Strata 8 Figure 18 and Appendix 2, Table 12 show habitat composition when the 13 cross sections in the strata are combined. The total strata reach (33 miles) represented by the] 3 cross sections (5.088 ft) is 2.9 %. Shallow (unusable) pools are the most common habitats available at flows between one and 60 cfs and between 80 and 400 cfs shallow runs are the most common habitat type Gross surface area increases at a faster rate with flow than usable habitat (Figure 19). The pcrccnt of usable habitat also increased with flow. The clusters in Strata 8 were found to have less Class I and Class II pools habitats than Strata 6. Area of usable habitat increased from 7% at I cfs to 23% at 400 cfs. The two clusters in this stratum had fairly different width/discharge relationships. At one cfs, Cluster] 15.5 has an average cross section width of64 ft, but it was 106 feet at cluster 94.0 (Figurc 20). Mean cross section width (n = 13) at 400 cfs was 235 ft, which is about 84% of the mean channcl width or bankfull flow width (280 ft). The coefficient of variation for average cross section width/discharge showed that width is 37