Hydrologic Cycle, a model

                Diagrammatic pathways of water going though Earth’s environmental spheres

 

STREAM FEATURES AND ASPECTS

                River, Creek, intermittent stream, etc.

                Banks, Bed, natural levee, bars, swales

                water confined to a channel, except in time of flood

                Floodplain

                Longtitudinal Profile

                Headwaters, mouth

                Cross-profile or cross-sectional profile

                V-shaped

 

SHEETWASH

                Unchanneled, thin sheet of flowing water

                Results in Sheet Erosion

 

Drainage Basin (aka watershed)

                Tributary

                Divide

                Examples:

                                Kautz Creek; Chehalis, Nisqually, Columbia, Amazon, and Mississippi Rivers

                NOTE: watersheds can contain smaller watersheds

 

Drainage Patterns

                As seen from above:

                                Dendritic - (most common)

                                Radial - common on domes or volcanoes

                                Trellis - in tilted or folded layered rock

 

Factors affecting stream erosion and deposition

                Velocity-

                                Distribution in cross-section

                Gradient: aka "rise over run", or amount of drop per unit length of stream

                                Usually decreases downstream

                                Effect on deposition and erosion

                Channel shape and roughness

                Discharge- (Q = vA)

                                Volume of water moving past a place in time

                                Usually given as cubic feet per second (cfs) or cubic meters/sec [m3/s]

                                Usually increases downstream

                                Nisqually River Discharge

                                                In McKenna: Average <1,000 cfs

                                                                Usual Range:

                                                                                Winter ?  cfs

                                                                                Last drought cfs

                                                                                1996 flood >50,000 cfs; Nov. 2006 flood ~ 20,000 cfs

 

Chehalis River

Length 115 mi (185 km) [1]

 

 

Stream Erosion

                Hydraulic action

                Solution- Dissolves rock

                Abrasion  (by sand and gravel)

                Potholes

                Deepens valley by eroding river bed

                Lateral erosion of banks on outside of curves

 

Transportation of Sediment

                Bed load

                Suspended load

                Dissolved load

 

Deposition

                Bars-

                                moved in floods

                                deposited as water slows

                                Placer Deposits (gold, etc.)

 

Braided Streams

                heavy load of sand and gravel

                commonly from glacier outwash streams

 

Meandering Streams

                Point bars on inside of curves

                Meander cutoff

                Oxbow lake

                Flood Plains

                                source of sediment/nutrients for farm soil

                Natural levees

 

Deltas & Alluvial Fans

                Delta

                                standing water slows stream

                                Distributaries

                Alluvial Fan

                                Decrease in gradient and minimized confinement slows velocity of stream

FLOODS

                Water overtops its banks

                Recurrence Interval

                                The 100 year flood--What it means

                Sacramento Floods of 1986

                                64  year flood

                Flood Control

                                Levees

                                Bypasses

                                Dams

                                                Problems with dams

 

Stream Valley Development

                Downcutting (abrasion of bed)

                V-shaped valley-

                If stream alone at work a slot canyon

                Steam + Mass wasting-- V-shaped valley

 

Base level

                Graded vs. ungraded stream:         -Stream attempts to establish an even grade through erosion and deposition

                Ungraded has

                                Pools

                                Rapids

                                Waterfalls

                                Lateral Erosion

                                                Valley widens by lateral erosion after downcutting becomes ineffective.

                                                Flood plain widens

 

Landscape Evolution (the traditional model)

                “Youth” Initially, flat uplands dissected by streams

                “Maturity” Then region in hillsides, with sharp divides

                “Old Age” Hills slowly erode down as floodplains widen

                Headward erosion

                Stream terraces

                Incised meanders

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This outline modified slightly from one compiled by Brian Hausback of Cal. State Sacramento. Last updated June 23, 2009