Streams: Outline Chapter 18 • Definition • Basins and divides: Colorado Rivers • Floods & Gradients Rivers and Streams Hydrologic Cycle Streams • A stream is a body of water that is confined in a channel and moves downhill under the influence of gravity. • This definition includes all sizes of running water from a tiny trickle to the Amazon. • The total area drained by a given stream is its drainage basin. Colorado Rivers Colorado DrainageN. Platte Basins Drainage Basins and Divides S. Platte Steamboat Boulder • The line separating one drainage basin from another is a drainage divide. • The Continental Divide separates Pueblo drainage basins of rivers that flow to Arkansas the Atlantic and Gulf of Mexico from Alamosa those flowing to the Pacific and Gulf Durango of Cortez (Gulf of California). Colorado RioGrande 1 Clicker Question Clicker Question • Water falling on Boulder goes down which • Water falling on Boulder goes down which river system? river system? – A. Colorado River to Gulf of California – A. Colorado River to Gulf of California – B. North Platte to Missouri River to Mississippi – B. North Platte to Missouri River to Mississippi River to Gulf of Mexico at New Orleans River to Gulf of Mexico at New Orleans – C. South Platte to Missouri River to – C. South Platte to Missouri River to Mississippi River to Gulf of Mexico at New Orleans Mississippi River to Gulf of Mexico at New Orleans – D. Arkansas River to Mississippi River to Gulf of – C. Arkansas River to Mississippi River to Gulf of Mexico at New Orleans Mexico at New Orleans – E. Rio Grande To Gulf of Mexico at Brownsville, – D. Rio Grande To Gulf of Mexico at Brownsville, TX TX Clicker Question Clicker Question • Water falling on Pueblo goes down which • Water falling on Pueblo goes down which river system? river system? – A. Colorado River to Gulf of California – A. Colorado River to Gulf of California – B. North Platte to Missouri River to Mississippi – B. North Platte to Missouri River to Mississippi River to Gulf of Mexico at New Orleans River to Gulf of Mexico at New Orleans – C. South Platte to Missouri River to Mississippi – C. South Platte to Missouri River to Mississippi River to Gulf of Mexico at New Orleans River to Gulf of Mexico at New Orleans – D. Arkansas River to Mississippi River to Gulf of – D. Arkansas River to Mississippi River to Mexico at New Orleans Gulf of Mexico at New Orleans – E. Rio Grande To Gulf of Mexico at Brownsville, – E. Rio Grande To Gulf of Mexico at Brownsville, TX TX Clicker Question Clicker Question • Water falling on Alamosa goes down which • Snow melting at Leadville goes down which river system? river system? – A. Colorado River to Gulf of California – A. Colorado River to Gulf of California – B. North Platte to Missouri River to Mississippi – B. North Platte to Missouri River to Mississippi River to Gulf of Mexico at New Orleans River to Gulf of Mexico at New Orleans – C. South Platte to Missouri River to Mississippi – C. South Platte to Missouri River to Mississippi River to Gulf of Mexico at New Orleans River to Gulf of Mexico at New Orleans – D. Arkansas River to Mississippi River to Gulf of – D. Arkansas River to Mississippi River to Gulf of Mexico at New Orleans Mexico at New Orleans – E. Rio Grande To Gulf of Mexico at Brownsville, – E. Rio Grande To Gulf of Mexico at Brownsville, TX TX 2 Clicker Question Clicker Question • Snow melting at Leadville goes down which • Snow melting at Breckenridge goes down river system? which river system? – A. Colorado River to Gulf of California – A. Blue River to Colorado River to Gulf of California – B. North Platte to Missouri River to Mississippi – B. North Platte to Missouri River to Mississippi River to Gulf of Mexico at New Orleans River to Gulf of Mexico at New Orleans – C. South Platte to Missouri River to Mississippi – C. South Platte to Missouri River to Mississippi River to Gulf of Mexico at New Orleans River to Gulf of Mexico at New Orleans – D. Arkansas River to Mississippi River to – D. Arkansas River to Mississippi River to Gulf of Gulf of Mexico at New Orleans Mexico at New Orleans – E. Rio Grande To Gulf of Mexico at Brownsville, – E. Rio Grande To Gulf of Mexico at Brownsville, TX TX Clicker Question Clicker Question • Snow melting at Breckenridge goes down • Snow melting at Steamboat Springs goes which river system? down which river system? – A. Blue River to Colorado River to Gulf of – A. Blue River to Colorado River to Gulf of California California – B. North Platte to Missouri River to Mississippi – B. North Platte to Missouri River to Mississippi River to Gulf of Mexico at New Orleans River to Gulf of Mexico at New Orleans – C. South Platte to Missouri River to Mississippi – C. Yampa River to Green River to Colorado River River to Gulf of Mexico at New Orleans to Gulf of California – D. Arkansas River to Mississippi River to Gulf of – D. Arkansas River to Mississippi River to Gulf of Mexico at New Orleans Mexico at New Orleans – E. Rio Grande To Gulf of Mexico at Brownsville, – E. Rio Grande To Gulf of Mexico at Brownsville, TX TX Clicker Question Clicker Question • Snow melting at Steamboat Springs goes • Water falling on Alamosa goes down which down which river system? river system? – A. Blue River to Colorado River to Gulf of – A. Colorado River to Gulf of California California – B. North Platte to Missouri River to Mississippi – B. North Platte to Missouri River to Mississippi River to Gulf of Mexico at New Orleans River to Gulf of Mexico at New Orleans – C. Yampa River to Green River to – C. South Platte to Missouri River to Mississippi Colorado River to Gulf of California River to Gulf of Mexico at New Orleans – D. Arkansas River to Mississippi River to Gulf of – D. Arkansas River to Mississippi River to Gulf of Mexico at New Orleans Mexico at New Orleans – E. Rio Grande To Gulf of Mexico at Brownsville, – E. Rio Grande To Gulf of Mexico at Brownsville, TX TX 3 Clicker Question Clicker Question • Snow melting at Durango goes down which • Snow melting at Purgatory (Durango) goes river system? down which river system? – A. Blue River to Colorado River to Gulf of – A. Blue River to Colorado River to Gulf of California California – B. Animas River to San Juan River to Colorado – B. Animas River to San Juan River to River to Gulf of California Colorado River to Gulf of California – C. Yampa River to Green River to Colorado River – C. Yampa River to Green River to Colorado River to Gulf of California to Gulf of California – D. Arkansas River to Mississippi River to Gulf of – D. Arkansas River to Mississippi River to Gulf of Mexico at New Orleans Mexico at New Orleans – E. Rio Grande To Gulf of Mexico at Brownsville, – E. Rio Grande To Gulf of Mexico at Brownsville, TX TX Colorado Drainage Basins Floods Steamboat Boulder • Flash floods can occur in a matter of hours as a result of a single storm. Pueblo • Flash floods are most likely in areas of high gradients. Alamosa • Annual floods result from Durango snowmelt or annual rain patterns (monsoons). Annual Floods Flash Flood, Boulder, 1894 4 Flash Flood, Boulder, 2013 Gradient • Gradient is the drop per mile (km). • Boulder Creek drops from 8000ft at Nederland to 5600’ in Boulder and has a gradient of 160 ft/mi (~30 m/km). • The Colorado River through Grand Canyon has a gradient of about 10 ft/mi (~2 m/km) • The lower Mississippi has a gradient of less than 0.5 ft/mi (~0.1 m/km). • Gradients usually decrease downstream. Gradient Decreases downstream Stream Velocity • Velocity is controlled by both gradient and channel size. • Steep gradients cause high velocities • Constricted channels cause high velocities. Discharge Discharge • Boulder Creek is typically 10-25 cfs, but may be 500 cfs or greater in May • Discharge is the total flow in ft3/s (cfs) and June. or m3/s. • The Colorado at Grand Junction is • 1 m3/s = ~35 ft3/s (cfs). typically 2000 cfs, but may exceed • In a section of stream with no 30,000 in May and June. tributaries, the discharge is constant • The lower Mississippi is typically while the velocity and channel size 250,000 cfs but exceeded 3 million may vary along the bed. cfs in 1993 flood. 5 Load Load • The load is the amount of material transported by a stream. – Dissolved load is the material in solution. – Suspended load is the material in suspension. – Bed load is the material on the bed • Saltation load is the material bouncing along the bottom. • Traction load is the material dragged along the bottom. Deposition and Erosion • The amount of bed load and suspended load vary with velocity. – Where a stream widens and slows, it deposits material. – Where a stream narrows and quickens, it erodes material. Deposition, Erosion, Bedrock Yellowstone and Valley Profiles channels River • Actively eroding streams valleys have a charac- teristic V-shape (no flood plain). • Actively depositing stream valleys have flat bottoms (flood plain). 6 V-shaped Valley Incised Meanders – meandering streams that were once “alluvial channels” near base level, but base level changed so they began to (Byers Canyon) downcut again…what happened here? – rise of the Colorado Plateau San Juan River, UT U-shaped Valley U-shaped/V-shaped Valley (Arlberg, Austria) (Val Feret, Suisse) Bars • Bars are material deposited by Flood streams. Plain – A point bar is a bar on the side of a stream. (Yampa) – A channel bar is a bar in the middle of a stream – A braided stream has many channels bars.