2-1 Stream Morphology24.pdf

School of Environment and Geomatics ENVR 150 Hydrology Learning Objectives  4-dimensions of stream  Stream morphology  Upper reaches  Lower reaches  Base level  Stream processes  Erosion  Transportation  Cap...

School of Environment and Geomatics ENVR 150 Hydrology Learning Objectives  4-dimensions of stream  Stream morphology  Upper reaches  Lower reaches  Base level  Stream processes  Erosion  Transportation  Capacity  Competence  Deposition 4-dimensional aspect of streams  Longitudinal dimension  Length of the stream  Lateral dimension  Width of flood plain  Vertical  Depth of stream  Interaction with aquifers (hyporheic)  30% of the river flows underground  Downwelling  Upwelling  Time  Daily  Seasonal  Annual Ward 1989 Stream Morphology Profile – slope and gradient From the headwaters to mouth (Base level)  Stream Morphology Pattern – birds eye view Meandering – move from side to side more common in the floodplain depositional zone Straight – often unnatural Braided – common near glaciers and near the mouth, high sediment load, very active little vegetation Anabranched – larger braids but with vegetated islands Meandering River Kettle River, Grand Forks BC Google Earth Stream Morphology Channelized (Straight) Channel between Anabranched Yukon River Okanagan Lake and Skaha Lake https://images.app.goo.gl/AyHqddK3ynQ6Sns27 Photo Credit: Sabine Stanzer 2020 Stream Morphology Latitudinal Profile X-section Main channel Side channels Size and distribution of sediment (substrate) Vegetation type and location along channel Riparian Areas Committee on Riparian Zone Functioning and Strategies for Management, Water Science and Technology Board, National Research Council Stream Morphology Channel Type Alluvial Channels formed in and by sediment which is transported by the river These channels are dynamic Non-Alluvial Bounded by bedrock or concrete Deeply cut into deposits Glade waterfalls, Non-Alluvial Stream Morphology Seneca College, Pressbooks Introduction to Geology and Geomorphology Kokanee Glacier Stream Profile (top to bottom)   Youthful stream - characterized by steeply cut channels, large lag boulders, rapids and nickpoints. Wilson Creek Kokanee Creek  Canyons Macbeth Creek Kokanee Creek Canyon Davis Creek (N of Kaslo) Stream Profile  Upper Reaches (headwaters) of the stream  Vertical erosion, V shaped valleys, Steep gradient  Rapids, Waterfalls, Gorges, Lag boulders  Lower Reaches  Lateral erosion, U shaped valleys, Gentle gradient  Terraces, flood plains, meanders, oxbows, point bars and cut banks  Alluvial deposits Stream Profile Lower Reaches  Floodplain – built and maintained by river channel under current river conditions  Fluvial Terrace – ancient floodplain formed under different climate and sediment transport conditions Terraces of Castlegar Terraces of Castlegar Floodplain Features Geosystems William River , Alaska Drainage Area 30 sq. mi. Streamway 120 * DA 0.43 = 518 ft 1997 1980 1966 1951 1989 Salt Creek Vinton County, Ohio Features Of A River Stream Profile  Upper Reaches (headwaters) of the stream  Vertical erosion, V shaped valleys, Steep gradient  Rapids, Waterfalls, Gorges, Lag boulders  Lower Reaches  Lateral erosion, U shaped valleys, Gentle gradient  Terraces, flood plains, meanders, oxbows, point bars and cut banks  Alluvial deposits  Base Level  Level at which no more erosion can occur  Alluvial Fan  Delta Base Levels Geosystems Figure 14.3 Alluvial Fan  A fan-shaped deposit of sediment found at ground level where a mountain river meets a flat valley or plain. Nile River Delta Geosystems Figure 14.25 Mackenzie River Delta Delta Can you guess which river this is? Fluvial Transport The WORK of a river Most erosion and transportation occur when stream flow is highest Geosystems, Figure 14.12 Fluvial Processes  3 Fluvial Processes 1. Erosion –(degradation) removes bi-products of weathering and mass wasting (cut banks, down cutting, terraces)  Physical weathering  Scouring – stream load breaks material down  Cavitation – the force of bubbles bursting  Chemical weathering  Minerals (salts) are dissolved in the water Fluvial Processes  3 Fluvial Processes con’t 2. Transportation – movement, dilution of wastes and redistribution of materials  Bedload  Saltation – materials are bounced along stream bed  Traction – materials are dragged  Suspension – held in the water by velocity (Turbidity)  Solution – dissolved load of the stream (Conductivity) 3. Deposition – Aggradation – as the stream slows sediments (alluvium) are deposited (floodplains, renews soils, levees, alluvial fans)  Fluvial Determinants  3 Variables affect a stream’s ability to carry out this work  Velocity  Discharge  Turbulence / Laminar  Capacity – total possible load a stream can transport (amount of material)  Competence - a stream’s ability to move particles of a particular size  D-95 = 95th percentile largest  D-50 = 50th percentile  Measured at B-axis diameter  Particle size Category Dia (mm) Wentworth scale Boulder > 256 < -8 Cobble Large 128 - 256 -7 Small 64 - 128 -6 www.mountainspecs.com/creek.jpg Pebble Large 32 - 64 -5 Small 16 - 32 -4 Gravel Coarse 8 - 16 -3 Medium 4-8 -2 Small 2-4 -1 Sand Very Coarse 1-2 0 www.aquatic.uoguelph.ca/rivers/chphys.htm Coarse 0.5 - 1 1 Medium 0.25 - 0.5 2 Fine 0.125 - 0.25 3 Very Fine 0.063 - 0.125 4 Silt < 0.063 >5 www.enn.com/news/enn-stories/2000/02/02172000/alaska.jpg Particle size tends to decrease in a downstream direction with bedrock and boulders being common in rocky headwater streams and sand predominating in lowland rivers.