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Sediment Analysis <br /> The pebble count results show the upstream reference reach, station 3250,has a higher <br /> percentage of sand and silt compared to station 4450. Sand and silt is also present at the <br /> downstream location,but it represents a smaller percentage of the grain size distribution <br /> (Figure 7). This might be explained by a few separate processes. First, it appears that non-native <br /> materials were added to the stream around station 4450. Second,hydraulic processes may be <br /> more effective at carrying the smaller sediments downstream. This could be a result of a smaller <br /> channel cross section producing higher velocities through the reach. Slope is not a driving factor <br /> as it is relatively continuous through the study area. If small grained sediment was carried <br /> downstream of station 4450,we expect that sediment will eventually appear in the restoration <br /> reach. <br /> A 7.9 kilogram bulk sediment sample was collected from the reference station 3250. The Dso <br /> pebble size (the grain diameter at which 50%is smaller)was estimated to be 8 mm. The <br /> reference reach is thus classified as a gravel bed stream. The D16 sediment size was estimated to <br /> be 0.46 mm, and the D&4 pebble size was 28 mm.The geometric standard deviation of sediment <br /> sizes o-g(D84/D16)°5 was 7.7,indicating a non-uniform sediment mix (Fryirs and Brierly,2012). <br /> These values were used to estimate sediment transport. Of consequence for habitat quality,the <br /> upstream bulk sample clarified that the sediment larger than 2 mm is mostly medium and <br /> coarse sand (Figure 8). <br /> Histogram Harbison Creek,Pebble Size Histogram <br /> st.4450% st.325 % om <br /> ME=_ i`_76 <br /> 5-15 <br /> 5. 0 _:.76 8? <br /> .4-• <br /> 38 97 76 `oft <br /> rsataax+.s133fi#eeM <br /> 20-30 24 26 4.95 _ o . <br /> 3t}43 5.88 2.97 lx i>.r 11 11 1040 <br /> 40.50 2.2 00.00, ` `• <br /> Figure 7.Pebble count results at stream stations 3250 and 4450. <br /> Histogram-Weight Harbison Creek,sulk Sample Partkle Histogram-weight <br /> bunit Sample <br /> she finer then(awn) %of tarts# '>O <br /> 0 15 1-r <br /> 0.177 0 5 = :, <br /> 0.21 20 <br /> 2 3.7. �Y taa __.. se e*crfs srrc�e.ae+.-s. .6 <br /> 5.6 t = „rr an as+7v <br /> 10 13.6. <br /> 20,. ..'... au ., •31+1 <br /> 30' 14.1'.'.40 6,6: aaeraesa... <br /> 50 4.9' <br /> Figure 8.Grain size distribution of the channel bed material at station 3250. <br /> 9 <br />