Lecture 5 - Flooding and Landslides Flashcards
What is a region that is drained by a single stream?
A drainage basin/watershed/river basin/catchment
Gradient of a river?
The drop in elevation over distance
Where is the gradient of a river highest/lowest?
Greatest in headwaters, lowest at the river mouth
Bed load?
The particles of sand and gravel that slide along the bottom of a channel in rapidly moving water
Suspended load?
Silt and clay particles carried in the water (90% of total load)
Dissolved load?
Ions that are carried in solution in water
Discharge?
The volume of water flowing through a cross section of a river per unit time (V*A=Q)
What forms where a river deposits sediment?
Alluvial fan (on land) or delta (in water)
Braided channel?
A large number of intersecting channels
Anastomosing channels?
Two or more channels with stable islands/bars where sediment is stored
Meandering channels?
Migrate back and forth across a floodplain
Cutbanks?
erosion on the outside of curves due to higher velocity
Point bars?
deposition on the inside of curves due to slower movement
Avulsion?
riber abandons a looping section of the old channel
When does flooding of a stream begin?
When the stream achieves bankfull discharge
Flood Discharge?
the level of river surface at a point (stage)
Flood stage?
indicates that a river has reached a level likely to cause property damage
Recurrence interval?
Avg time between floods
Where do flashfloods occur?
Upper parts of watersheds and in small tributary basins of large rivers
What causes a flash flood?
Large quantities of rain in a short time
Downstream Flood?
- affect larger areas than flashfloods, more destructive
- produced by storms of long duration, or rapid melting of snowpacks
Glacial Lake Outburst Floods (GLOF)
Sudden-onset outburst floods that result from the failure of a moraine-dam, ice dam
Where are many GLOFs found?
SHIT TONS IN PERU
Dykes?
Thick wall constructed to prevent flooding
