USGS Scientific Investigations Report 2012–5017  - Geomorphic Setting, Aquatic Habitat, and Water-Quality Conditions of the Molalla River, Oregon, 2009

Table 14. Physical characteristics for five sites sampled for water quality and algae in the Molalla River, Oregon. 

[Abbreviations: D₁₀, size of sediment for which 10 percent of the sample is finer; D₅₀, median particle size; D₉₀, size of sediment for which 90 percent of the sample is finer; FPkm, flood plain kilometer; km, kilometer; km², square kilometer; LiDAR, light detection and ranging; m, meter; mm, millimeter; m/m, meter per meter; m/s, meter per second; m/yr, meter per year; m²/m, square meter per meter; m³/s, cubic meter per second; n/a, no data available]

Variable	Molalla River sampling site
Variable	Upstream of Glen Avon Bridge	Upstream of Highway 211 Bridge	Upstream of Highway 213 Bridge	Upstream of Goods Bridge	Downstream of Knights Bridge
Instream/site characteristics
	Dominant land cover
	Forested	Forested/ rural/ agricultural	Rural/ agricultural/ forested	Rural/ agricultural	Rural/ agricultural/ urban
Elevation (m)	163	97	72	33	23
LiDAR river stationing (km)	44.20	31.07	23.40	10.50	4.75
D₁₀ particle size (mm)	32	38	29	25	14
D₅₀ particle size (mm)	108	71	95	71	41
D₉₀ particle size (mm)	316	157	156	139	77
Sand, percent	1.25	0.0	0	2	5.5
Drainage area (km²)	344	531	546	842	893
Low flow discharge (10 percent exceedance) (m³/s)	0.90	1.39	1.43	2.21	2.34
Median discharge (50 percent exceedance) (m³/s)	7.72	11.9	12.3	18.9	20.0
Bankfull discharge (2-year flood) (m³/s)	157	243	250	385	408
Water velocity at low flow, 90 percent exceedance (m/s)	0.39	0.52	0.45	0.47	0.54
Water velocity at median discharge, 50 percent exceedance (m/s)	0.83	1.06	1.00	0.91	1.04
Water velocity at bankfull discharge (2-year flood) (m/s)	2.41	2.56	2.27	2.53	2.79
Averaged residual pool depth (m)	n/a	0.4	1.7	0.7	0.4
Average water surface slope for 1 kilometer reach (m/m)	0.005	0.004	0.003	0.002	0.001
Presence of local streambed bedrock	Yes	Yes	Yes	No	Yes
Presence of local gravel bars	No	Yes	Yes	Yes	No
Flood-plain and channel characteristics
Geomorphic flood plain FPkm segment (km)	36	25	20	10	4
FPkm segment average flood plain width (km)	0.21	1.13	0.90	0.83	2.66
Local flood plain width, (km)	0.10	0.98	0.98	0.70	2.25
1994 active channel width (m)	29.5	38.8	44.7	44.1	30.3
2000 active channel width (m)	27.1	47.1	60.8	52.3	34.5
2005 active channel width (m)	27.4	35.1	39.8	47.5	35.0
2009 active channel width (m)	31.2	33.9	45.9	56.7	35.7
Averaged active channel width (m)	28.8	38.7	47.8	50.1	33.9
1994–2000 annual migration rate (m/yr)	1.02	2.27	3.43	1.62	1.11
2000–2005 annual migration rate (m/yr)	1.00	0.55	0.88	1.15	0.48
2005–2009 annual migration rate (m/yr)	1.36	1.58	1.92	3.70	2.05
Time-weighted annual migration rate (m/yr)	1.10	1.52	2.19	2.00	1.14
Gemorphic reach average percent confined banks	44.9	21.1	21.1	15.1	24.2
FPkm segment average percent confined banks	23.4	48.1	26.0	41.2	51.3
Local bank confinement (number: 0,1,2 banks confined)	0	2	0	2	2
1994 channel sinuosity	1.10	1.35	1.35	1.29	1.05
2000 channel sinuosity	1.12	1.39	1.39	1.45	1.08
2005 channel sinuosity	1.10	1.39	1.39	1.44	1.08
2009 channel sinuosity	1.10	1.40	1.40	1.29	1.09
Average sinuosity	1.10	1.38	1.38	1.37	1.07
2009 specific bar area in FPkm segment (m²/m)	6.68	24.73	56.60	19.47	8.31
2009 percentage of bare vegetation on bars	55.15	83.36	37.96	30.85	74.43
2009 percentage of moderate vegetation on bars	0	0	56.66	69.15	14.47
2009 percentage of dense vegetation on bars	44.85	16.64	5.38	0	11.10

Geomorphic Setting, Aquatic Habitat, and Water-Quality Conditions of the Molalla River, Oregon, 2009–10

Geomorphic Setting, Aquatic Habitat, and Water-Quality Conditions of the Molalla River, Oregon, 2009–10 