1. Stream Morphology Assessment Greg Jennings, PhD, PE Professor, Biological & Agricultural Engineering North Carolina State University jennings@ncsu.edu Barbara Doll, PE Jan Patterson, PE Jason Zink, PE Zan Price, PE Kris Bass, PE Justin Church, PE Mike Geenen, EI Mike Shaffer, EI Karen Hall Dave Penrose
46. Watershed: “Area of land that drains water, sediment, and dissolved materials to a common outlet at some point along a stream channel” Dunne and Leopold, 1978 Watershed form is influenced by: Climate Geology & Soils Fluvial Geomorphology Vegetation Land Uses
47. From Webster's Revised Unabridged Dictionary (1913) : Watershed, n [Cf. G. wasserscheide; wasserwater + scheidea place where two things separate, fr. scheidento separate.] The whole region or extent of country which contributes to the supply of a river or lake. The line of division between two adjacent rivers or lakes with respect to the flow of water by natural channels into them; the natural boundary of a basin. Other Terms: Catchment, Drainage basin, River basin
50. Water Transport & Storage Hydrology: The study of the flow of the earth’s waters through the hydrologic cycle Hydrograph: Displays change in flow (discharge over time Peak Flow Rising Limb Falling Limb Mean Daily Flow www.Geology.com
54. Water Transport to Streams Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
55. Land use in a watershed affects:- water quality- water quantity- ecosystem services
57. Strahler Stream Order Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
58. USGS Topographic Map – 1:24,000 scale Courtesy of John Dorney and Perianne Russell, NC Division of Water Quality
61. Contributing Drainage Areas for Stream Origins(Ephemeral to Intermittent/Perennial) Courtesy of John Dorney and Perianne Russell, NC Division of Water Quality
62. Problems with Contiguous USGS Maps Headwater stream shown on one map and not the other Tributaries shown on one map and not the other McDaniel Bald and Marble Quadrangles, Cherokee County, NC Courtesy of John Dorney and Perianne Russell, NC Division of Water Quality
63. Groundwater Influences Streamflow Losing Stream Gaining Stream Groundwater Recharge Groundwater Discharge Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
78. Biological communities upstream and downstreamStream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
79. Field Investigations What is living in the stream? What are the physical and chemical conditions of the stream?
81. Stream Ecosystems Mostly downstream fluxes of energy and matter Lateral and vertical connections to the riparian and hyporheic zones Courtesy of Francois Birgand, NCSU
90. Abrasion of heavy materials rolling on bottomhttp://www.uwsp.edu/gEo/faculty/ritter/geog101/textbook/fluvial_systems/geologic_work_of_streams.html
91. Transportation: Movement of material by water Stream Load includes: dissolved + suspended + bed load Capacity: maximum load that can be transported for a given discharge (increases with velocity and turbulence) Competence: largest size material that can be transported for a given discharge http://www.uwsp.edu/gEo/faculty/ritter/geog101/textbook/fluvial_systems/geologic_work_of_streams.html
93. Deposition: Aggradation: Raising the bed elevation Bars: Depositional areas that may change flow directions http://www.uwsp.edu/gEo/faculty/ritter/geog101/textbook/fluvial_systems/geologic_work_of_streams.html
94. Bed Material (Substrate) Silt/Clay: < 0.062 mm Sand: 0.062 – 2 mm Gravel: 2 – 64 mm Cobble: 64 – 256 mm Boulder: 256 – 2048 mm
107. Meandering Stream: Alluvial Forms Flow Downstream Floodplain Scarp Bankfull Stage Point Bar Pool Left Bank Right Bank Riffle Thalweg
108. Bankfull Stage “corresponds to the discharge at which channel maintenance is the most effective, that is, the discharge at which moving sediment, forming or removing bars, forming or changing bends and meanders, and generally doing work results in the average morphologic characteristics” (Dunne and Leopold,1978) Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
115. Valley type affects stream morphology Colluvium is loose sediment transported by gravity and deposited at the bottom of a slope. Alluvium is sediment deposited by a river in the channel or floodplain Alluvial valleys occur where sediment particles are dropped by slow-moving water.
116. Valley Types: (www.epa.gov/watertrain/stream_class) Valley Type II Moderately steep, gentle sloping side slopes often in colluvial valleys From EPA Watershed Academy: Fundamentals of the Rosgen Stream Classification System
117. Valley Types: (www.epa.gov/watertrain/stream_class) Valley Type VIII Wide, gentle valley slope with well-developed floodplain adjacent to river terraces From EPA Watershed Academy: Fundamentals of the Rosgen Stream Classification System
118. Stream Corridor Lateral Profile Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
129. Pool Cross-Section (Meandering Stream) Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
134. Oxbow Formation in Meandering Streams Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
156. Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
157. Step Pool Streams (high gradient) Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
166. Natural Stream Channel Stability (from Leopold) River has a stable dimension, pattern and profile Maintains channel features (riffles, pools, steps) Does not aggrade (fills) or degrade (erodes)
175. Velocity & Discharge Q = VA = Discharge (cfs) V = Velocity (ft/s) A = Cross-Section Area (ft2) V related to slope, channel shape, and channel roughness Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
178. A = 40 sq ft W = 22 ft R = 1.7 ft S = 0.010 ft/ft n = 0.040 V = 5.0 ft/s Q = 200 cfs A = 220 sq ft W = 55 ft R = 3.5 ft S = 0.004 ft/ft n = 0.035 V = 6.1 ft/s Q = 1350 cfs
184. Shear Stress: fluid force per unit area acting on the streambed = Rs = Shear Stress (lb/ft2) = Unit Weight of Water = 62.4 lb/ft3 R = Hydraulic Radius (ft) = A / P S = Average Water Surface Slope (ft/ft) A = Riffle Cross-Section Area (ft2) P = Wetted Perimeter (ft) P = Wbkf +2*Dbkf (approx)
191. Bankfull Discharge Flow fills active channel and spreads onto floodplain Represents break between channel & floodplain processes For channel in equilibrium, assumed to equal the effective discharge Return Period typically 1 to 2 years
192. Bankfull Stage “corresponds to the discharge at which channel maintenance is the most effective, that is, the discharge at which moving sediment, forming or removing bars, forming or changing bends and meanders, and generally doing work results in the average morphologic characteristics” (Dunne and Leopold,1978) Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
224. Entrenchment Ratio ER = Wfpa / Wbkf Wfpa = Width of Flood Prone Area measured at the elevation twice bankfull max depth above thalweg Wbkf = Width of Bankfull Channel Wfpa Bankfull 2 x dmax above thalweg dmax Wbkf
226. Rocky Branch Phase II Reach 2: Priority 2 (floodplain excavation, C channel) Entrenchment Ratio = Wfpa / Wbkf = 90/20 = 4.5 Wfpa Wbkf Flood water flows onto floodplain several times each year
227. Rocky Branch Phase II Reach 1: Priority 3 (floodplain excavation, Bc channel) Entrenchment Ratio = Wfpa / Wbkf = 40/20 = 2 Wfpa Wbkf
228. Bank Height Ratio BHR = dmax tob/ dmax dmax tob= Max Depth from top of low bank to thalweg dmax = Max Depth from bankfull stage to thalweg Bankfull dmax tob dmax
229. BHR = 5.3 / 2.5 = 2.1 Top of Bank Bankfull dmax tob dmax
230. Pattern: Plan form Alluvial (low-gradient) streams naturally meander across a valley with a somewhat predictable pattern
231. Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
232. Sinuosity = stream length / valley length K = 1850 / 980 = 1.9 Valley Length
240. Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
241. Step Pool Streams (high gradient) Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
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