AND RUNNING WATER Hydrologic Cycle •What happens to precipitation •, Creek, etc. • Banks, Bed • Confined to a –Except in time of • •Longtitudinal Profile Headwaters, mouth Cross-profile V-shaped

SHEETWASH –Unchanneled, thin sheet of flowing water – Results in Sheet • • Divide • Examples: –Mississippi River – Amazon River

Drainage Patterns •As seen from above • Dendritic (most common) • Radial • Trellis- in tilted or folded layered

Factors affecting stream erosion and •Velocity- –Distribution in cross-section •Gradient –Usually decreases downstream – Effect on deposition and erosion •Channel shape and roughness • - –Volume of water moving past a place in time •Usually given as cubic feet per second (cfs) –Usually increases downstream •Discharge- –Volume of water moving past a place in time •Usually given as cubic feet per second (cfs) –Usually increases downstream American River Discharge •In Sacramento: • Average 3,741 c.f.s. • Usual Range: –Winter 9,000 cfs – Last drought 250 cfs •1986 flood 130,000 cfs Stream Erosion •Hydraulic action • Solution- Dissolves rock • Abrasion (by and gravel) –Potholes •Deepens by eroding river bed • Lateral erosion of banks on outside of curves Transportation of • • • Deposition •Bars- –moved in – deposited as water slows – Placer Deposits (gold, etc.) – Braided Streams •heavy load of sand and gravel • commonly from outwash streams Meandering Streams •Point bars on inside of curves • cutoff – •Flood Plains –Importance to farm soil – Natural Deltas & Alluvial Fans •Delta –standing water slows stream – • –Decrease in gradient 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 • –Levees – Bypasses – •Problems with dams

Stream Valley Development • (abrasion of bed) • V-shaped valley- –If stream alone at work a slot – 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 • • Lateral Erosion •Valley widens by lateral erosion –after downcutting becomes ineffective – Flood plain widens

Landscape Evolution •“Youth” Initially, flat uplands dissected by streams • “Maturity” Then region in hillsides, with sharp divides • “Old Age” Hills slowly erode down as widen • • Stream terraces • Incised