Site Evaluations Lower Eightmile Creek Site Information Site Location: Mt Hood NF, east of cascade crest, Forest Road 4440 Year Installed: 2000 Lat/Long: 121°26”32.90”W 45°24”47.89”N Watershed Area (mi2):4.78 Stream Slope (ft/ft)1: 0.037 Channel Type: Step-pool Bankfull Width (ft): 16.5 Survey Date: April 26 2007 1 Water surface slope extending up to 20 channel widths up and downstream of crossing. Culvert Information Culvert Type: Open-bottom arch Culvert Material: Annular CMP Culvert Width: 12 ft Outlet Type: Mitered Culvert Length: 55 ft Inlet Type: Mitered Pipe Slope (structure slope): 0.024 Culvert Bed Slope: 0.026 (First hydraulic control upstream of inlet to first hydraulic control downstream of outlet.) Culvert width as a percentage of bankfull width: 0.73 Alignment Conditions: Appears OK. May have been slight adjustment from original stream channel. Bed Conditions: Coarse angular material in pipe. Some material has aggraded in upstream half of pipe. Some riprap material from inlet sides possibly being recruited into pipe. Pipe Condition: Good condition. Hydrology Discharge (cfs) for indicated recurrence interval 25% 2-yr Qbf2 2-year 5-year 10-year 50-year 100-year 43 50 171 236 287 418 478 Bankfull flow estimated by matching modeled water surface elevations to field-identified bankfull elevations. 2 Lower Eightmile Creek A—159 Culvert Scour Assessment LOWER EIGHTMILE CREEK Points represent survey points Figure 1—Plan view map. A—160 Lower Eightmile Creek Site Evaluations History Survey Summary There is no information available for site history. Sixteen cross sections and a longitudinal profile were surveyed along Lower Eightmile Creek in April 2007 to characterize the culvert and an upstream and downstream representative reach. Representative sections in the culvert were taken through a pool and steep riffle. Two additional cross sections were surveyed upstream to characterize the inlet as well as the contraction of flow. Another two cross sections were surveyed downstream of the culvert to characterize the outlet and the expansion of flow. Site Description The Lower Eightmile culvert is a bottomless arch mitered to conform to the slope of the road fill. It is a relatively new installation (2000). The upstream portion of the culvert is characterized by a wide and deep pool that drops into a series of steps/steep riffles through the culvert to the outlet. Large angular bed material makes up the bed through the downstream portion of the culvert. An upstream and downstream representative reach were identified at this site. The upstream representative reach consists of a series of three wood jams that account for most of the drop in grade through the reach. Backwater pools, riffles, and short steps are interspersed between the three jams. Fines have accumulated in the backwater pools created by the jams. A low active flood plain with large conifers and small underbrush line both banks. The downstream representative reach begins as a relatively steep and evenly graded riffle. At the downstream end, the channel opens up into a wide backwater pool. A low flood-plain surface on the right bank, similar to the upstream reference reach, contributes wood to the channel. Whereas no log jams were present in the representative reach, large wood was present both in and around the channel. The lack of wood jams may be a result of the maintenance of the channel due to its proximity to a campground area on the left bank. Lower Eightmile Creek In the upstream representative reach, representative cross sections were taken through a pool and a riffle. An additional two sections were taken to characterize the upstream and downstream boundaries of the reach. In the downstream representative reach, representative cross sections were taken through a step and a pool. An additional two sections were taken to characterize the upstream and downstream boundaries of the reach. Profile Analysis Segment Summary The profile analysis resulted in a total of 14 profile segments. Two segments with similar gradient in the upstream channel were not combined in order to separate out the inlet transition segment (segment I) from the upstream representative segment K. The culvert consisted of two profile segments. The downstream segment in the culvert was comparable to two representative profile segments, one in the upstream channel and one in the downstream channel. The upstream segment in the culvert was comparable to one representative profile segment in the downstream channel. The upstream transition A—161 Culvert Scour Assessment segment was comparable to three representative profile segments, two in the upstream channel and one in the downstream channel. One downstream transition segment was comparable to an upstream and a downstream representative segment and one was comparable just to a downstream representative segment. See figure 2 and table 1. Scour Conditions Substrate – The bed material in the pool in the upstream portion of the culvert has more coarse material and fewer fines than pools in the upstream and downstream channels. This pool is more glide-like (higher velocity and less residual depth) than the pools in the natural channel. The step in the culvert also has more coarse material than the riffles/steps in the natural channel. The D84 and D95s are both larger in the culvert than in the riffle and step units in the natural channel. There are also fewer fines in the culvert. Observed conditions Footing scour – Footings are exposed throughout much of the culvert but they are not scoured to the base of the footings and they generally appear in good condition. The riprap placed around the culvert and along the road fill has remained in place. Culvert-bed adjustment – There are no obvious signs of bed adjustment except for some recently aggraded sediment in the upstream half of the culvert. There is angular rock forming a step in the downstream portion of the culvert; it is unknown whether this was placed during construction or if it washed in from the riprap banks at the inlet. Profile characteristics – The profile has a convex shape through the crossing with a rise in bed elevation within the culvert (figure 2). Residual depths – Culvert residual depths are lower than residual depths in corresponding channel segments (C, J, and A) (figure 21). The upstream transition segment (I) has residual depths that are both greater and less than the range of residual depths in corresponding profile segments (D, J, and L). The single residual depth in downstream transition segment F is lower than the single depth in corresponding profile segment L. A—162 Predicted conditions Cross-section characteristics – Modeling suggests that the culvert has a large effect on flow geometry. The culvert exhibits signs of inlet control conditions. Backwatered conditions create subcritical flow upstream of the inlet that transitions to supercritical or near supercritical within the pipe. The flow geometry therefore changes dramatically within the culvert (figures 5 through 7 and 12 through 19). Flow area, wetted perimeter, and top width are reduced whereas hydraulic radius and depth are increased, particularly near the upstream end of the culvert. Transition areas are also affected, particularly the upstream transition (I) where widths and depths are elevated above what is found in corresponding profile segments in the natural channel (D, J, and L). Shear stress – Shear stress is low at the inlet because of backwater effects but increases towards the downstream end of the culvert and is very high at the outlet area (figure 10). The downstream transition area (F) exhibits the greatest shear stress (figures 10 and 19). The upstream transition (I) has low shear stress because of the effect of culvert backwater on the energy grade slope. Lower Eightmile Creek Site Evaluations Excess shear – Model results show that the culvert excess shear stress is within the range of channel conditions (figure 20) except at high flows (Q50 and above) where culvert bed mobility may exceed that of the natural channel. AOP Conditions Velocity – Velocity is low at the inlet because of backwater effects but increases towards the downstream end of the culvert and is very high at the outlet area (figure 11). The downstream transition area (F) exhibits the greatest velocity (figures 11 and 18). The upstream transition (I) has low velocity because of the effect of culvert backwater on the energy grade slope. Profile complexity – Vertical sinuosity in the culvert segments were equal to or lower than corresponding profile segments in the natural channel (table 4). Vertical sinuosity in the upstream transition (I) was within the range of corresponding profile segments (D, J, and L). Vertical sinuosity in the downstream transition segments (E and F) were equal to or lower than corresponding profile segments in the natural channel (D, L, and C). Scour summary Currently there are no significant signs of scour in the pipe. The rise in bed elevation in the culvert appears to be related to the step that makes up the downstream half of the pipe. This step is composed of angular large cobbles and small boulders and may be riprap material washed into the culvert from the banks at the inlet. There is streambed material (rounded alluvium) that has aggraded upstream of this step. The grade control provided by the step, and the associated aggradation in the upstream half of the pipe, may be limiting culvert capacity and creating scour risk during high flows. Hydraulic modeling at this site indicates inlet control conditions at high flows. High shear stress and velocity at the downstream end of the pipe may create scour risk. This site is a relatively recent installation (year 2000) has not yet experienced large flood flows. This site is likely to experience considerable adjustment during future floods, which may scour material from the pipe, as well as flatten and coarsen the bed. Lower Eightmile Creek Cross-section complexity – The sum of squared height differences in the culvert cross sections are both greater than those in the channel cross sections (table 3). Depth distribution – The upstream cross section in the culvert had less shallow channel margin habitat than the natural channel but the downstream cross-section value was within the range of the natural channel (table 5). Habitat units – The culvert has more glide habitat and less pool habitat than the channel outside the crossing (table 6). Residual depths – Culvert residual depths are lower than residual depths in corresponding channel segments (C, J, and A) (figure 21). The upstream transition segment (I) has residual depths that are both greater and less than the range of residual depths in corresponding profile segments (D, J, and L). The single residual depth in downstream transition segment F is lower than the single depth in corresponding profile segment L. A—163 Culvert Scour Assessment Substrate – The bed material in the pool in the upstream portion of the culvert has more coarse material and fewer fines than pools in the upstream and downstream channels. This pool is more glide-like (higher velocity and less residual depth) than the pools in the natural channel. The step in the culvert also has more coarse material than the riffles/steps in the natural channel. The D84 and D95 are both larger in the culvert than in the riffle and step units in the natural channel. There are also fewer fines in the culvert. Large woody debris – There was a very small amount of LWD present in the culvert (table 8). The natural channel had moderate to very high LWD abundance. LWD formed steps and scour pools in the channel outside the crossing and played a primary role in habitat unit creation and complexity. Features in the culvert did not mimic the role of wood in the natural channel. AOP summary Visual observations of the culvert bed indicate significantly less complexity than the natural channel bed. Large wood plays an important role in creating steps and complexity in the natural channel and this dynamic is not present in the culvert. The rock step in the culvert is unlike anything found in the natural channel. The natural channel either has free-formed riffles of gravels or cobbles or wood-forced steps. The complexity metrics used in the analysis do not adequately reflect these observations. A—164 Flow in the culvert was wall-to-wall throughout much of its length at the time of the survey. At low summer flows, wide shallow flow may create fish passage issues. At higher flows, the high velocity in the downstream portion of the pipe may also impede passage, especially considering the lack of bank roughness that can provide velocity refuge. There were patches of exposed banks observed during the survey but they were discontinuous and would not create suitable conditions for passage of terrestrial organisms at the observed flow. Design Considerations Hydraulic analysis and observations at other sample sites suggest that this site may experience bed adjustment during future high flows. The culvert appears to have insufficient capacity to adequately convey high flows. Contributing factors may include an inadequate culvert size and the presence of aggraded material within the pipe. Design improvements would include a larger culvert (current culvert is less than 75 percent of the bankfull width) and a properly constructed bed that creates a more uniform profile through the crossing. Constructed bed elements could include banks that provide flow concentration and roughness (velocity refuge) for fish passage and that also would provide exposed banks to facilitate passage of terrestrial organisms. Lower Eightmile Creek Lower Eightmile Creek Relative elevation (ft) 29 42 47 30 31 33 18 41 G H I J K L M N 400 D L C D J L I I I D o w n s trea m T ra n s itio n F F E C J A R epres en ta tiv e C h a n n el S eg men t G G H U ps trea m T ra n s itio n C u lv ert S eg men t Table 1—Segment comparisons D XS 3: Pebble count (step) Representative Channel XS 2: Pebble count (pool) 0 .0 1 3 0 .0 4 9 0 .0 4 0 0 .0 3 7 0 .0 0 6 0 .0 5 5 0 .0 2 9 0 .0 6 2 0 .0 3 7 0 .0 5 8 0 .0 2 3 XS 4 21.6% 5.6% 7.4% 0.1% 5.3% 25.9% 4.5% 28.1% 25.9% % D ifferen c e in G ra d ien t Figure 2—Lower Eightmile Creek longitudinal profile. 80 85 500 13 F XS 1 30 E B 62 D A 0 .0 2 8 14 C C 0 .0 6 4 23 B 0 .0 0 7 28 A S e g m e n t G r a d ie n t S e g m e n t L e n g th (ft) S egment 90 elevation (feet) Relative 95 100 105 110 E XS 6 XS 7: Pebble count (step) G D is ta nc e a long bed (feet) 300 XS 5 F H XS 9 XS 11 I 200 XS 10 XS 8: Pebble count (pool) C ulvert XS 12 J XS 13: Pebble count (riffle) K XS 15: Pebble count (pool) 100 Representative Channel XS 14 L M N XS 16 0 Site Evaluations A—165 A—166 n o i t a v e l E ) t f ( F G H I J L 0 * 5 . 1 * * 1 2 3 4 5 . . . . . 2 2 2 2 2 0.1009 – 0.1138 0.1049 – 0.1256 0.1079 – 0.1191 0.0997 – 0.1105 0.1058 – 0.1115 0.1093 – 0.1209 0.1052 – 0.1244 0.0861 – 0.1052 2 1 3 2 1 1 1 1 1 2 3 5 5 5 4 2 5 7 3 3 # of interpolated XSs * 6 4 . 3 * 4 6 . 3 * 2 8 . 3 4 100 * * * 5 5 2 4 6 9 2 . . . . . 4 4 4 4 5 5 7 . 6 6 7 1 1 * 6 . 1 2 1 1 * 3 5 1 . . . 2 2 3 1 1 1 300 Main Channel Dis tance (ft) * 3 3 3 5 3 5 8 5 7 . . . . . 0 0 7 7 8 8 9 1 1 200 * 5 2 . 3 1 * 5 4 4 . . 3 3 1 1 4 1 * 5 . 4 5 1 1 * 3 . 5 1 5 . 5 1 * 6 . 5 1 400 * 7 . 5 1 Stations with decimal values are interpolated cross sections placed along the surveyed profile. * 8 2 . 3 Figure 3—HEC-RAS profile. 85 90 95 100 105 110 E 115 D 0.0876 – 0.0945 0.08 – 0.0832 # of measured XSs 8 . 5 1 6 1 500 Obtained using equation from Jarrett (1984): n = 0.39S0.38R-0.16, where S=stream slope; R=hydraulic radius. Jarrett’s equation only applied within the following ranges: S = 0.002 to 0.08, R = 0.5 ft to 7 ft. For cross sections outside these ranges, n was computed either from adjacent sections that fell within the ranges, using the guidance of Arcement and Schneider (1987), or from the HEC-RAS recommendations for culvert modeling. C 1 A SegmentRange of Manning’s n values1 Table 2—Summary of segments used for comparisons Ground W S Qbf W S Q2 W S Q10 W S Q50 W S Q100 L e ge nd Culvert Scour Assessment Lower Eightmile Creek Lower Eightmile Creek Elevation (ft) n o i t a v e l E ) t f ( n o i t a v e l E ) t f ( 100 0 20 40 .1009 0 Station (ft) RS = 14 Station (ft) 60 .1009 20 .11 80 40 .11 100 60 Bank St a Ground WS Qbf WS Q2 WS Q10 WS Q50 WS Q100 L e ge nd Bank St a Ground WS Qbf WS Q2 WS Q10 WS Q50 WS Q100 L e ge nd n o i t a v e l E ) t f ( Elevation (ft) 0 98 100 102 104 106 108 110 102 104 106 108 110 112 -20 20 .1073 0 .1049 40 .1073 60 Station (ft) 20 .1049 RS = 13 Station (ft) RS = 15 .1073 40 .1049 80 60 100 L e ge nd B a n k S ta L e ve e G ro u n d W S Qb f W S Q2 W S Q1 0 W S Q5 0 W S Q1 0 0 L e ge n d Bank St a Ground WS Qbf WS Q2 WS Q10 WS Q50 WS Q100 Figure 4—Cross-section plots. Only measured cross sections are included. Manning’s n values are included at the top of the cross section. The stationing (RS) corresponds to the stationing on the HEC-RAS profile. Green arrows define the ineffective flow areas. Black arrows represent points surveyed in as the bankfull channel boundary. Only those points identified in the field and supported by hydraulic and topographic analyses are marked below. Elevation (ft) 102 104 106 .1009 -20 .11 n o i t a v e l E Elevation (ft) 108 110 112 102 -40 104 106 108 110 112 114 RS = 16 ) t f ( Site Evaluations A—167 n o i t a v e l E ) t f ( Elevation (ft) n o i t a v e l E ) t f ( A—168 96 20 40 20 Station (ft) 60 .1079 RS = 10 Station (ft) 40 .1115 80 .1079 60 .1115 100 80 B a n k S ta In e ff G ro u n d W S Qb f W S Q2 W S Q1 0 W S Q5 0 W S Q1 0 0 L e ge n d Bank St a Ground WS Qbf WS Q2 WS Q10 WS Q50 WS Q100 L e ge nd n o i t a v e l E ) t f ( Elevation (ft) 96 98 100 102 104 106 108 0 96 98 100 102 104 106 108 0 20 .1077 20 .1162 40 .1077 40 Station (ft) RS = 9 Station (ft) 60 60 .1162 RS = 11 .1077 80 80 .1162 B a n k S ta In e ff G ro u n d W S Qb f W S Q2 W S Q1 0 W S Q5 0 W S Q1 0 0 L e ge n d Bank St a Ground WS Qbf WS Q2 WS Q10 WS Q50 100 100 L e ge nd WS Q100 Figure 4—Cross-section plots. Only measured cross sections are included. Manning’s n values are included at the top of the cross section. The stationing (RS) corresponds to the stationing on the HEC-RAS profile. Green arrows define the ineffective flow areas. Black arrows represent points surveyed in as the bankfull channel boundary. Only those points identified in the field and supported by hydraulic and topographic analyses are marked below. (continued) Elevation (ft) 98 100 102 .1079 0 .1115 n o i t a v e l E Elevation (ft) 104 106 108 98 -20 100 102 104 106 108 110 RS = 12 ) t f ( Culvert Scour Assessment Lower Eightmile Creek Lower Eightmile Creek Elevation (ft) n o i t a v e l E ) t f ( n o i t a v e l E ) t f ( 94 -40 -20 .118 0 0 Station (ft) .118 RS = 6 Station (ft) . 1 1 8 20 20 40 40 60 60 B a n k S ta In e ff G ro u n d W S Qb f W S Q2 W S Q1 0 W S Q5 0 W S Q1 0 0 L e ge n d n o i t a v e l E ) t f ( Elevation (ft) -20 94 96 98 100 102 104 -40 96 98 100 102 104 106 0 -20 .1244 0 20 20 Station (ft) .1244 RS = 5 Station (ft) .0946 40 . 1 2 4 4 RS = 7 Note: n values for first profile. 40 60 60 L e ge nd 80 B a n k S ta In e ff G ro u n d W S Qb f W S Q2 W S Q1 0 W S Q5 0 W S Q1 0 0 L e ge n d Bank St a Ground WS Qbf WS Q2 WS Q10 WS Q50 WS Q100 Figure 4—Cross-section plots. Only measured cross sections are included. Manning’s n values are included at the top of the cross section. The stationing (RS) corresponds to the stationing on the HEC-RAS profile. Green arrows define the ineffective flow areas. Black arrows represent points surveyed in as the bankfull channel boundary. Only those points identified in the field and supported by hydraulic and topographic analyses are marked below. (continued) Elevation (ft) 96 98 100 -20 Bank St a Ground WS Qbf WS Q2 WS Q10 WS Q50 WS Q100 L e ge nd n o i t a v e l E Elevation (ft) 102 104 106 96 -40 98 100 102 104 106 108 .0882 RS = 8 Note: n values for first profile. ) t f ( Site Evaluations A—169 n o i t a v e l E ) t f ( Elevation (ft) n o i t a v e l E ) t f ( A—170 88 20 .08 40 RS = 2 60 60 Station (ft) Station (ft) 40 .08 .0861 80 80 100 Bank St a Ground WS Qbf WS Q2 WS Q10 WS Q50 WS Q100 L e ge nd 100 B a n k S ta L e ve e G ro u n d W S Qb f W S Q2 W S Q1 0 W S Q5 0 W S Q1 0 0 L e ge n d n o i t a v e l E ) t f ( Elevation (ft) 88 20 90 92 94 96 98 100 90 92 94 96 98 100 102 40 .0819 20 .0877 40 60 Station (ft) .0819 RS = 1 80 Station (ft) 60 .0877 RS = 3 .0819 80 100 .0877 100 120 L e ge n d Bank St a Ground WS Qbf WS Q2 WS Q10 WS Q50 WS Q100 L e ge nd B a n k S ta L e ve e G ro u n d W S Qb f W S Q2 W S Q1 0 W S Q5 0 W S Q1 0 0 Figure 4—Cross-section plots. Only measured cross sections are included. Manning’s n values are included at the top of the cross section. The stationing (RS) corresponds to the stationing on the HEC-RAS profile. Green arrows define the ineffective flow areas. Black arrows represent points surveyed in as the bankfull channel boundary. Only those points identified in the field and supported by hydraulic and topographic analyses are marked below. (continued) Elevation (ft) 90 92 .08 20 .0861 n o i t a v e l E Elevation (ft) 94 96 98 0 0 100 92 94 96 98 100 102 .0861 RS = 4 ) t f ( Culvert Scour Assessment Lower Eightmile Creek Lower Eightmile Creek . P . W l a t o T 0 50 100 150 200 250 300 0 A 50 B C 100 D W.P. total (ft) A—171 0 A 50 B C Figure 6—Wetted perimeter. 10 20 30 40 50 60 70 80 100 D Figure 5—Flow area (total) profile plot. Flow area (sq ft) ) t f ( w o l F a e r A q s ( ) t f E E 150 150 200 Culvert H 250 I 200 Culvert H 250 I Main Channel Distance (ft) F G Main Channel Distance (ft) F G 300 J 300 J K K 350 350 L L M N 400 N Flow 400 M Flow 450 450 W.P. Total Qbf W.P. Total Q2 W.P. Total Q10 W.P. Total Q50 W.P. Total Q100 Legend Flow Area Qbf Flow Area Q2 Flow Area Q10 Flow Area Q50 Flow Area Q100 Legend Site Evaluations A—172 p o T h t d i W 0 1 2 3 4 5 6 7 0 A 50 B C 0 0 A 50 B C Figure 8—Top width. Top width (ft) 20 40 60 80 100 Figure 7—Hydraulic radius. Hydraulic radius (ft) ) t f ( r d y H s u i d a R ) t f ( 100 D 100 D E E 150 150 200 Culvert H 250 I 200 Culvert H 250 I Main Channel Distance (ft) F G Main Channel Distance (ft) F G 300 J 300 J K 350 350 K L L 400 M Flow 400 M Flow N N 450 450 Top Width Qbf Top Width Q2 Top Width Q10 Top Width Q50 Top Width Q100 Legend Hydr Radius Qbf Hydr Radius Q2 Hydr Radius Q10 Hydr Radius Q50 Hydr Radius Q100 Legend Culvert Scour Assessment Lower Eightmile Creek r a e h S n a h C q s / b l ( 100 E E 150 F G 200 Culvert H 250 I 300 J J 350 K L L 400 M Flow N N 450 Max Chl Dpth Q100 Legend 1 2 3 4 5 Lower Eightmile Creek 0 A 50 B C 100 D Figure 10—Shear stress (channel) profile. Shear channel (lbs/sq ft) 0 10 20 30 40 150 200 Culvert H 250 I Main Channel Distance (ft) F G Main Channel Distance (ft) 300 350 K 400 M Flow 450 Shear Chan Qbf Shear Chan Q2 Shear Chan Q10 Shear Chan Q50 Shear Chan Q100 Legend Max Chl Dpth Qbf Max Chl Dpth Q2 Max Chl Dpth Q10 50 D 6 0 B C Max Chl Dpth Q50 A 7 8 9 Figure 9—Maximum depth. Maximum channel depth (ft) ) t f x a M l h C h t p D ) t f ( Site Evaluations A—173 ) s / t f ( A—174 l e V l n h C 0 0 50 100 Figure 11—Velocity (channel) profile plot. Velocity channel (ft/s) 2 4 6 8 10 12 150 250 Main Channel Distance (ft) 200 300 350 400 450 Vel Chnl Qbf Vel Chnl Q2 Vel Chnl Q10 Vel Chnl Q50 Vel Chnl Q100 Legend Culvert Scour Assessment Lower Eightmile Creek Flow area (ft2) A—175 J L A C D A L J G (Culv) H (Culv) F (DS Trans) Qbf H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) E (DS Trans) D A C D I (US Trans) Figure 12—Flow area (total). 0 50 A 100 Flow Area (ft2) 150 200 250 300 50% of the values A L I (US Trans) J H (Culv) E (DS Trans) F (DS Trans) H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) G (Culv) 2 D J L A C D 100% of the values G (Culv) H (Culv) E (DS Trans) F (DS Trans) C J L A C D Minimum value 25th percentile 10 J L A C D A L J H (Culv) E (DS Trans) F (DS Trans) 50 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) G (Culv) Median (aka 50th percentile) 75th percentile Maximum value A L J H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) I (US Trans) Box Plot Explanation I (US Trans) D C Lower Eightmile Creek C L L I (US Trans) J G (Culv) H (Culv) E (DS Trans) F (DS Trans) 100 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) J Site Evaluations D C D C H (Culv) A C D C C G (Culv) H (Culv) G (Culv) J J L A C D 2 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) F (DS Trans) F (DS Trans) F (DS Trans) Qbf D D A C D E (DS Trans) E (DS Trans) F (DS Trans) 2 H (Culv) L J L J L H (Culv) I (US Trans) A A H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) I (US Trans) Figure 14—Hydraulic radius. 0 I (US Trans) J E (DS Trans) Hydraulic Radius (ft) 1 2 3 4 5 6 7 G (Culv) G (Culv) Qbf 10 L A C D J L A C D 10 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) G (Culv) L L F (DS Trans) F (DS Trans) A A G (Culv) H (Culv) A A C C J H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) H (Culv) I (US Trans) H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) I (US Trans) J C C D D L L H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) E (DS Trans) E (DS Trans) A A J L J A C D 50 A C D 50 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) J L H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) F (DS Trans) F (DS Trans) J H (Culv) A C D H (Culv) I (US Trans) J L I (US Trans) J D D C C G (Culv) G (Culv) I (US Trans) J Figure 13—Wetted perimeter. Hydraulic Radius (ft) E (DS Trans) D D L L J L A C D E (DS Trans) E (DS Trans) A A A C D D D 0 J L L J H (Culv) 100 L 100 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) J H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) G (Culv) 20 Wetted Perimeter (ft) C C F (DS Trans) F (DS Trans) 40 E (DS Trans) E (DS Trans) G (Culv) H (Culv) 60 I (US Trans) I (US Trans) A—176 J Wetted perimeter (ft) L 80 Culvert Scour Assessment Lower Eightmile Creek F (DS Trans) J L J H (Culv) H (Culv) G (Culv) H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) F (DS Trans) Qbf C C A C D J J L A C D 2 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) F (DS Trans) A A F (DS Trans) 2 H (Culv) L J L H (Culv) I (US Trans) D A C D I (US Trans) I (US Trans) Figure 16—Maximum depth. 0 I (US Trans) J E (DS Trans) 2 Maximum Depth (ft) 4 6 8 D D L L G (Culv) Figure 15—Top width. E (DS Trans) E (DS Trans) G (Culv) G (Culv) Qbf H (Culv) J L A C D 10 10 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) J L A C D H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) G (Culv) A A F (DS Trans) F (DS Trans) H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) C C G (Culv) H (Culv) H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) D D J J A C D I (US Trans) I (US Trans) J L E (DS Trans) E (DS Trans) L L J L A C D D D A A J L J A C D 50 A C D 50 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) J L H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) F (DS Trans) F (DS Trans) A C D H (Culv) 0 C C G (Culv) G (Culv) 15 H (Culv) I (US Trans) 45 I (US Trans) J 60 E (DS Trans) E (DS Trans) L L 75 D D 90 J L L H (Culv) 100 L 100 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) J H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) G (Culv) A A F (DS Trans) F (DS Trans) A A C C G (Culv) H (Culv) C C E (DS Trans) E (DS Trans) J J 30 Top Width (ft) Maximum depth (ft) D I (US Trans) I (US Trans) Lower Eightmile Creek L Top width (ft) E (DS Trans) Site Evaluations A—177 C C I (US Trans) I (US Trans) H (Culv) H (Culv) F (DS Trans) F (DS Trans) H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) J L A C D J L A C D 2 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) F (DS Trans) G (Culv) G (Culv) Qbf E (DS Trans) E (DS Trans) E (DS Trans) E (DS Trans) A C D H (Culv) H (Culv) J J Figure 18—Velocity (channel). 0 I (US Trans) I (US Trans) D Velocity 3 (ft/sec) 6 9 12 D D J J A A F (DS Trans) 2 C C L L Figure 17—Width-to-depth ratio. G (Culv) G (Culv) Qbf 10 J L A C D J L A C D 10 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) F (DS Trans) L L F (DS Trans) H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) E (DS Trans) E (DS Trans) H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) H (Culv) H (Culv) A A G (Culv) G (Culv) H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) I (US Trans) I (US Trans) A C D D D J J J L C C L L J L A C D 50 A C D 50 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) J L H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) F (DS Trans) F (DS Trans) J L A C D E (DS Trans) E (DS Trans) A C D H (Culv) H (Culv) A A G (Culv) G (Culv) 0 I (US Trans) I (US Trans) 20 D D J J 30 C C 40 D D L L J L L J 100 L 100 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) J H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) F (DS Trans) F (DS Trans) A A E (DS Trans) E (DS Trans) C C H (Culv) H (Culv) A A G (Culv) G (Culv) 10 Width-to-depth Ratio Velocity (ft/sec) D I (US Trans) I (US Trans) A—178 J Width-to-depth ratio L 50 Culvert Scour Assessment Lower Eightmile Creek Shear stress (lbs/ft2) A C D L I (US Trans) J G (Culv) H (Culv) F (DS Trans) Qbf H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) Excess shear (Applied/tcrit) D C A 200 300 C Dis charge (cfs ) G (Culv) F (DS Trans) 2 I (US Trans) H (Culv) 500 C 600 L A C D L I (US Trans) J G (Culv) H (Culv) E (DS Trans) F (DS Trans) 10 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) J D L J D DS Channel (US pebble count) - step Culvert (DS pebble count) - step size. Values of excess shear greater than 1 indicate bed movement for the D84 particle size. Figure 20—Excess shear stress. C US Channel (DS pebble count) - riffle A C D A Excess shear stress is the channel shear divided by the critical shear for bed entrainment of the D84 particle Excess Shear (Applied / tcrit) 0 0 100 2 4 6 8 J L A H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) E (DS Trans) 400 J L A C D A Figure 19—Shear stress (channel). 0 E (DS Trans) Lower Eightmile Creek 10 Shear Stress (lbs/ft2) 20 30 40 A C D A L I (US Trans) J G (Culv) H (Culv) E (DS Trans) F (DS Trans) 50 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) J L L L I (US Trans) J G (Culv) H (Culv) E (DS Trans) F (DS Trans) 100 H (culv) G (culv) I (us trans) F (ds trans) E (ds trans) J Site Evaluations A—179 D C D Culvert Scour Assessment Table 3—Sum of squared height difference Reach XSUnit type Location Culvert Sum of squared height difference Within range of channel conditions? US Pool 0.09 No DS Step 0.10 No US Pool 0.04 DS Riffle 0.08 US Step 0.06 DS Pool 0.05 Upstream Downstream Table 4—Vertical sinuosity Segment A DS channel 1.001 B DS channel 1.000 C DS channel 1.009 D DS channel 1.001 E DS transition 1.004 F DS transition 1.001 G Culvert 1.007 H Culvert 1.001 I US transition 1.003 J US channel 1.012 K US channel 1.009 L US channel 1.004v M US channel 1.005 N US channel 1.003 A—180 LocationVertical Sinuosity (ft/ft) Lower Eightmile Creek Site Evaluations Table 5—Depth distribution Reach XS Location 25% Q2 Culvert Within range of channel conditions? US 0 No DS 3 Yes US 8 DS 3 US 1 DS 8 Upstream Downstream Table 6—Habitat unit composition Percent of surface area Reach Pool Glide Riffle Step Culvert 12% 47% 33% 0% Upstream Channel 70% 4% 12% 14% Downstream Channel 32% 0% 53% 15% 1.2 Residual Depth (ft) 1.0 0.8 0.6 0.4 Residual depth (ft) 0.2 Segment N Segment M Segment L Segment K Segment J Segment I US Transition Segment H Culvert Segment G Culvert Segment F DS Transition Segment E DS Transition Segment D Segment C Segment B Segment A 0.0 Culvert Culvert Segment Segment J Segment L SegmentSegment A Segment B Segment C D K Segment N Segment M Segment H:Transition Segment G: Segment Segment E: DS Transition F: DS Transition Segment I: US Figure 21­—Residual depths. Lower Eightmile Creek A—181 Culvert Scour Assessment Table 7—Bed material sorting and skewness Reach XSUnit Sorting Location Type Culvert Within range Skewness of channel conditions? Within range of channel conditions? US Pool 2.27 Yes 0.26 Yes DS Step 1.22 No -0.15 No US Pool 2.06 0.35 DS Riffle 3.17 0.36 US Step 1.59 0.35 DS Pool 2.64 0.00 Upstream Downstream Table 8—Large woody debris Reach Culvert Pieces/Channel Width 0.3 Terminology: US = Upstream DS = Downstream Upstream 5.49 RR = Reference reach Downstream 1.73 XS = Cross section View upstream through culvert. A—182 View downstream through culvert. Lower Eightmile Creek Site Evaluations Downstream reference reach - upstream Downstream reference reach – downstream pebble count, riffle. pebble count, pool. Upstream reference reach – upstream pebble count, pool. Upstream reference reach – downstream pebble count, riffle. Culvert – downstream pebble count, riffle. Lower Eightmile Creek Culvert – upstream pebble count, pool. A—183 Culvert Scour Assessment Cross section: Upstream Reference Reach – Upstream Pebble Count Material sand very fine gravel fine gravel fine gravel medium gravel medium gravel coarse gravel coarse gravel very coarse gravel very coarse gravel small cobble medium cobble large cobble very large cobble small boulder small boulder medium boulder large boulder very large boulder bedrock S ize C las s (mm) C ount Item % C umulative % 35 4 1 2 8 13 10 15 5 5 1 0 1 0 0 0 0 0 0 0 35% 4% 1% 2% 8% 13% 10% 15% 5% 5% 1% 0% 1% 0% 0% 0% 0% 0% 0% 0% 35% 39% 40% 42% 50% 63% 73% 88% 93% 98% 99% 99% 100% 100% 100% 100% 100% 100% 100% 100% <2 2-4 4 - 5.7 5.7 - 8 8 - 11.3 11.3 - 16 16 - 22.6 22.6 - 32 32 - 45 45 - 64 64 - 90 90 - 128 128 - 180 180 - 256 256 - 362 362 - 512 512 - 1024 1024 - 2048 2048 - 4096 Bedrock 40 100% 35 90% Frequency 70% 25 60% 20 50% 40% Frequency 15 30% 10 20% 5 Cumulative Frequency 10% Bedrock 2048-4096 512-1024 1024-2048 362-512 256-362 180-256 128-180 64-90 90-128 45-64 32-45 22.6-32 16-22.6 8-11.3 11.3-16 5.7-8 <2 4-5.7 <2 0% 2-4 0 2-4 4 - 5.7 - 8 32 -45 45-64 64- 90 8 - 11.3 90 - 128 Bedrock 11.316- 16 -22.6 22.6- 32 128180 - 180 256 - 256 362 - 362 - 512 512 - 1024 Particle Size Category (mm) 1024 2048 - 2048 - 4096 Particle Size Category (mm) S ize C las s S ize perc ent finer than (mm) D5 D16 D50 D84 D95 D100 1 1 12 28 50 140 A—184 Cumulative Frequency 80% 30 Sorting Coefficient: Material P erc ent C ompos ition Sand Gravel Cobble Boulder Bedrock 35% 63% 2% 0% 0% 2.06 Skewness Coefficient: 0.35 Lower Eightmile Creek Site Evaluations Cross section: Upstream Reference Reach – Downstream Pebble Count Material sand very fine gravel fine gravel fine gravel medium gravel medium gravel coarse gravel coarse gravel very coarse gravel very coarse gravel small cobble medium cobble large cobble very large cobble small boulder small boulder medium boulder large boulder very large boulder bedrock S ize C las s (mm) C ount Item % C umulative % 16 1 1 1 1 3 4 10 8 7 5 8 8 7 4 0 4 0 0 0 18% 1% 1% 1% 1% 3% 5% 11% 9% 8% 6% 9% 9% 8% 5% 0% 5% 0% 0% 0% 18% 19% 20% 22% 23% 26% 31% 42% 51% 59% 65% 74% 83% 91% 95% 95% 100% 100% 100% 100% <2 2-4 4 - 5.7 5.7 - 8 8 - 11.3 11.3 - 16 16 - 22.6 22.6 - 32 32 - 45 45 - 64 64 - 90 90 - 128 128 - 180 180 - 256 256 - 362 362 - 512 512 - 1024 1024 - 2048 2048 - 4096 Bedrock 100% 16 90% 14 80% 70% Frequency 12 60% 10 50% 8 Frequency 6 40% 30% Bedrock 2048-4096 1024-2048 362-512 512-1024 256-362 180-256 90-128 128-180 64-90 45-64 32-45 22.6-32 Cumulative Frequency 2-4 4 - 5.7 - 8 32 -45 45-64 64- 90 8 - 11.3 90 - 128 Bedrock 11.316- 16 -22.6 22.6- 32 128180 - 180 256 - 256 362 - 362 - 512 Particle Size Category (mm) 512 - 1024 1024 2048 - 2048 - 4096 Particle Size Category (mm) S ize C las s S ize perc ent finer than (mm) D5 D16 D50 D84 D95 D100 1 1 43 200 313 530 Lower Eightmile Creek 11.3-16 <2 16-22.6 0% 5.7-8 0 8-11.3 10% 4-5.7 2 <2 20% 2-4 4 Cumulative Frequency 18 Sorting Coefficient: Material P erc ent C ompos ition Sand Gravel Cobble Boulder Bedrock 18% 41% 32% 9% 0% 3.17 Skewness Coefficient: 0.36 A—185 Culvert Scour Assessment Cross section: Culvert – Upstream Pebble Count Material sand very fine gravel fine gravel fine gravel medium gravel medium gravel coarse gravel coarse gravel very coarse gravel very coarse gravel small cobble medium cobble large cobble very large cobble small boulder small boulder medium boulder large boulder very large boulder bedrock S ize C las s (mm) <2 2-4 4 - 5.7 5.7 - 8 8 - 11.3 11.3 - 16 16 - 22.6 22.6 - 32 32 - 45 45 - 64 64 - 90 90 - 128 128 - 180 180 - 256 256 - 362 362 - 512 512 - 1024 1024 - 2048 2048 - 4096 Bedrock C ount Item % C umulative % 9 1 0 5 7 8 10 3 2 10 13 14 6 6 6 0 0 0 0 0 9% 1% 0% 5% 7% 8% 10% 3% 2% 10% 13% 14% 6% 6% 6% 0% 0% 0% 0% 0% 9% 10% 10% 15% 22% 30% 40% 43% 45% 55% 68% 82% 88% 94% 100% 100% 100% 100% 100% 100% 16 100% 14 90% Frequency 70% 10 60% 8 50% 40% Frequency 6 30% 4 20% Bedrock 2048-4096 1024-2048 362-512 512-1024 256-362 180-256 90-128 128-180 64-90 45-64 32-45 22.6-32 11.3-16 Cumulative Frequency 2-4 4 - 5.7 - 8 32 -45 45-64 64- 90 8 - 11.3 90 - 128 Bedrock 11.316- 16 -22.6 22.6- 32 180 - 180 256 - 256 362 - 362 - 512 Particle Size Category 128 (mm) 512 - 1024 1024 2048 - 2048 - 4096 Particle Size Category (mm) S ize C las s S ize perc ent finer than (mm) D5 D16 D50 D84 D95 D100 1 10 50 180 262 330 A—186 16-22.6 5.7-8 <2 8-11.3 0% 4-5.7 0 <2 10% 2-4 2 Cumulative Frequency 80% 12 Sorting Coefficient: Material P erc ent C ompos ition Sand Gravel Cobble Boulder Bedrock 9% 46% 39% 6% 0% 2.27 Skewness Coefficient:0.26 Lower Eightmile Creek Site Evaluations Cross section: Culvert – Downstream Pebble Count Material sand very fine gravel fine gravel fine gravel medium gravel medium gravel coarse gravel coarse gravel very coarse gravel very coarse gravel small cobble medium cobble large cobble very large cobble small boulder small boulder medium boulder large boulder very large boulder bedrock S ize R ange (mm) C ount Item % C umulative % 0 0 0 0 0 1 2 2 3 10 16 18 7 7 12 8 6 0 0 0 0% 0% 0% 0% 0% 1% 2% 2% 3% 11% 17% 20% 8% 8% 13% 9% 7% 0% 0% 0% 0% 0% 0% 0% 0% 1% 3% 5% 9% 20% 37% 57% 64% 72% 85% 93% 100% 100% 100% 100% <2 2-4 4 - 5.7 5.7 - 8 8 - 11.3 11.3 - 16 16 - 22.6 22.6 - 32 32 - 45 45 - 64 64 - 90 90 - 128 128 - 180 180 - 256 256 - 362 362 - 512 512 - 1024 1024 - 2048 2048 - 4096 > 4096 100% 20 80% Frequency 16 14 60% 12 40% 10 8 Frequency 6 20% 4 Cumulative Frequency 18 0% Cumulative Frequency 2 Bedrock 2048-4096 1024-2048 362-512 512-1024 256-362 180-256 128-180 64-90 90-128 45-64 32-45 22.6-32 16-22.6 11.3-16 5.7-8 8-11.3 <2 4-5.7 <2 -20% 2-4 0 2-4 4 - 5.7 5.7 - 8 > 4096 32 -45 45-64 64- 90 8 - 11.3 90 - 128 11.316 - 16 -22.6 22.6- 32 128180 - 180 256 - 256 362 - 362 - 512 512 1024 Particle Size Category (mm) 1024 2048 - 2048 - 4096 Particle Size Category (mm) S ize C las s S ize perc ent finer than (mm) D5 D16 D50 D84 D95 D100 36 60 120 350 525 550 Lower Eightmile Creek Sorting Coefficient: Material P erc ent C ompos ition Sand Gravel Cobble Boulder Bedrock 0% 20% 52% 28% 0% 1.22 Skewness Coefficient:-0.15 A—187 Culvert Scour Assessment Cross section: Downstream Reference Reach – Upstream Pebble Count Material sand very fine gravel fine gravel fine gravel medium gravel medium gravel coarse gravel coarse gravel very coarse gravel very coarse gravel small cobble medium cobble large cobble very large cobble small boulder small boulder medium boulder large boulder very large boulder bedrock S ize C las s (mm) C ount Item % C umulative % 2 0 1 1 2 4 4 1 6 6 8 8 16 13 16 9 1 0 0 0 2% 0% 1% 1% 2% 4% 4% 1% 6% 6% 8% 8% 16% 13% 16% 9% 1% 0% 0% 0% 2% 2% 3% 4% 6% 10% 14% 15% 21% 28% 36% 44% 60% 73% 90% 99% 100% 100% 100% 100% <2 2-4 4 - 5.7 5.7 - 8 8 - 11.3 11.3 - 16 16 - 22.6 22.6 - 32 32 - 45 45 - 64 64 - 90 90 - 128 128 - 180 180 - 256 256 - 362 362 - 512 512 - 1024 1024 - 2048 2048 - 4096 Bedrock 100% 16 90% 80% Frequency 14 70% 12 60% 10 50% 8 Frequency 6 40% 30% 4 20% 2 10% Cumulative Frequency Bedrock 2048-4096 512-1024 1024-2048 362-512 256-362 180-256 128-180 64-90 90-128 45-64 32-45 22.6-32 16-22.6 8-11.3 11.3-16 5.7-8 <2 4-5.7 <2 0% 2-4 0 Cumulative Frequency 18 2-4 4 - 5.7 5.7 - 8 32 -45 45-64 64- 90 8 - 11.3 90 - 128 Bedrock 11.316- 16 -22.6 22.6- 32 128180 - 180 256 - 256 362 - 362 - 512 512 - 1024 Particle Size Category (mm) 1024 2048 - 2048 - 4096 Particle Size Category (mm) S ize C las s S ize perc ent finer than (mm) D5 D16 D50 D84 D95 D100 10 35 140 300 420 550 A—188 Sorting Coefficient: Material P erc ent C ompos ition Sand Gravel Cobble Boulder Bedrock 2% 26% 46% 27% 0% 1.59 Skewness Coefficient: 0.35 Lower Eightmile Creek Site Evaluations Cross section: Downstream Reference Reach – Downstream Pebble Count Material sand very fine gravel fine gravel fine gravel medium gravel medium gravel coarse gravel coarse gravel very coarse gravel very coarse gravel small cobble medium cobble large cobble very large cobble small boulder small boulder medium boulder large boulder very large boulder bedrock S ize C las s (mm) C ount Item % C umulative % 32 4 3 7 6 4 5 10 11 6 3 0 2 0 4 0 2 0 0 0 32% 4% 3% 7% 6% 4% 5% 10% 11% 6% 3% 0% 2% 0% 4% 0% 2% 0% 0% 0% 32% 36% 39% 46% 53% 57% 62% 72% 83% 89% 92% 92% 94% 94% 98% 98% 100% 100% 100% 100% <2 2-4 4 - 5.7 5.7 - 8 8 - 11.3 11.3 - 16 16 - 22.6 22.6 - 32 32 - 45 45 - 64 64 - 90 90 - 128 128 - 180 180 - 256 256 - 362 362 - 512 512 - 1024 1024 - 2048 2048 - 4096 Bedrock 100% 35 80% Frequency 25 70% 60% 20 50% 15 Frequency 40% 30% 10 20% 5 Cumulative Frequency 10% Bedrock 2048-4096 1024-2048 362-512 512-1024 256-362 180-256 128-180 64-90 90-128 45-64 32-45 22.6-32 11.3-16 16-22.6 5.7-8 8-11.3 2-4 <2 4-5.7 0% <2 0 2-4 4 - 5.7 - 8 32 -45 45-64 64- 90 8 - 11.3 90 - 128 Bedrock 11.316- 16 -22.6 22.6- 32 128180 - 180 256 - 256 362 - 362 - 512 512 - 1024 Particle Size Category (mm) 1024 2048 - 2048 - 4096 Particle Size Category (mm) S ize C las s S ize perc ent finer than (mm) D5 D16 D50 D84 D95 D100 1 1 10 50 271 700 Lower Eightmile Creek Cumulative Frequency 90% 30 Sorting Coefficient: Material P erc ent C ompos ition Sand Gravel Cobble Boulder Bedrock 32% 57% 5% 6% 0% 2.64 Skewness Coefficient: 0.00 A—189