geo quiz 6

retaining walls, counterwight fills, benched slopes, rock bolts, drainage

engineering methods of enhancing slope stability

rotational slump

dominant failure mechanism for soil slopes

watershed

network of stream segments joining together

drainage divides

boundaries of river basins

first order

no tributaries

second order

merging of first order streams

headward erosion

extension of river channels in the upstream directions

stream capture (piracy)

interception of one stream by another

1-2 m/yr

retreat rate of niagara falls

waterfalls

formed by contact between rock types of different erosional resistance at river bed

stream velocity

function of slope of channel and distance from sides or bed

at surface in the middle of channel

where maximum velocity occurs in a river

0.6depth

mean velocity

load

total amount of sediemnt carried by stream

dissolved load

carried in solution

suspended load

carried in small particles

bed load

carried by large particles, roll and slide along bed

terminal velocity

balance between gravity and viscous resistance

meandering

favored by gently sloping area, low sediment supply, and cohesive sediments

cut bank

outside bank with greater velocity and erosion occuring

point bar

inside bank with lower velocity and deposition occuring

natural levee

coarse sediment deposited adjacent to channel margins

backswamps

organic-rich, fine-grained sediment, high water table

oxbow lake

formed by growth and abandonment of a meander, cutoff

skunk river

river in ames they tried to straighten by dredging, didn’t work that well

braided streams

broad shallow channels, with multiple sub channels. favored by high gradient and abundant source of coarse sediment

alluvial fans

emergence of a stream form a mountain front onto a basin

deltas

coastal counterparts of alluvial fans, river enters sea, decrease in velocity and deposition of coarse load near river mouth

avulsion

abandonment of an active part in preference of an adjacent part with steeper gradient

atchafalaya

mississippi river flow is shifting to

old river control structure

built by us army corps of engineers to prevent capture of mississippi river by atchafalaya

flood magnitude

elevation to which a river rises or maximum discharge

stage

river height

rating curve

river stage vs discharge

stream hydrograph

river stage or discharge vs time

flood frequency

probability of occurrencer

recurrence interval

inversely proportional to frequency

ri

statistical average

length of record available and peak measured discharge

flood frequency curves depend on

urbanization and tile drainage

land use changes that influence flood frequency curves

structural approach

control of river system by channelization, levees, dams

nonstructural approach

restriction of flood-prone areas to non-built environments

abyssal hills

ocean topography: more subdued relief

abyssal plans

ocean topography: landscape buried by continental sediment

continental shelves

ocean topography: gently sloping, submerged parts of the continentssu

submarine canyons

ocean topography: cut by rivers when shelves were exposed

continental slopes

ocean topography: steep slope after shelf

continental rise

ocean topography: marks transition from continental crust to ocean basins

turbidity currents

transportation of huge volumes of sediment onto abyssal plains

turbidites

graded bedding exposed in marine rocks on land

wavelength

distance between adjacent crests or troughs

period

amount of time for a full oscillation at a point

circular orbits

particle movement for waves in deep water

below ½ wavelength

where there is negligible water movement in deep water

fetch

distance of wind action, limiting factor for lakes and ponds

storm duration, wind speed, fetch

factors affecting wave formation size

swell

arrangement of waves with similar periods in regular near-sinusoidal disturbances

pile up height, drop in velocity

waves approaching shore

refraction

bending of wavefronts

headlands

wave energy focused here, causing greater erosion

bays

lower wave energy here, causing deposition