XII. Streams A.The Hydrologic Cycle (components and pathways) B.Stream Velocity (controls and results) C.Drainage Patterns and Landscape Features (results of erosion and deposition) D.Stream Valley Development (tectonic uplift and downcutting)

The Hydrologic Cycle See Fig. 12.3

Systems of streams and their tributaries that collect runoff Divide Ground Water Drainage Basins Great Lakes Drainage Basin

Steam Profiles (Streams Shaping the Land) V-Shaped Valley Flood Plain

What is this Drainage Pattern? (What does is tell of the geology?)

Valley and Ridge Province of PA (Trellis Stream Patters)

Stream Gradient Slope of the land Sinuosity of stream 10 m/km 10 m per 1¼ km = 8 m/km 10 m 1 km 10 m 1 km

Meander Velocity Higher velocities on outside of meanders causes erosion (cut bank) Lower velocities on inside of meanders causes deposition (point bar) Fig. 10.6

Channel Shape and Roughness A. Narrow and Deep Less resistance Faster flow B. Wide and Shallow More resistance Slower flow C. Rough Streambed More resistance Slower flow

Stream Velocity Controls: How much and what grainsize of sediment is Eroded and Transported Where and what grainsize size will be sediment

Stream Erosion Then, Erosion Solution (chemical weathering) Hydraulic Action (lifting) Abrasion (crushing and grinding) Pg First, Weathering Fracturing (mechanical) Loosening (mechanical and chemical) Solution (chemical)

Stream Transport Dissolved Load Suspended Load Bed Load Saltation Rolling, sliding Pg. 276 (ions)

Stream Deposition Braided Streams Alluvial Fan e.g., Alluvial Fans Fig a Fig b Erosion Dominated High gradients Less resistance Fast velocities Deposition Dominated Lower gradients More resistance Lower velocities

Stream Deposition Midchannel bars Fig. 12.7b Point bars Fig 12.9 Braided streams Fig. 12.7a

Deltas Fig Reduction of velocity due to extreme widening Deposition of silt and clay

Erosion and Deposition  Transport E.g., Meandering streams As meanders are migrating Cutbanks eroding Point bars building Sediment is moving downstream

Meander Cutoff How does the gradient change with meandering and meander cutoff?

Meandering Streams Identify Cutbanks Point bars Meander neck Oxbow lakes Areas of Erosion Areas of Deposition A A B B C C D D E E

Flooding Overbank deposits Widening of stream into flood plain Deposition of sediment Coarse near stream Fine farther away Natural Levees Fig

Graded Streams Increased velocity and accelerated erosion. Erosion acts to grade the Longitudinal stream profile to concave-upward curve Base level: Lake or Sea Same Base level

Drainage Patterns Geology controls stream patterns A.Uniformly Erodible (e.g., flat-lying sedimentary rocks of the Midwest) B.Conical Mountains (e.g., Volcanoes) C.Fractured bedrock (shallow bedrock) D.Resistant ridges of tilted sedimentary rocks (e.g., Valley and Ridge Province of Pennsylvania) A. Dendritic B. Radial C. Rectangular D. Trellis