rivers and floods Flashcards
What is the representation of water stored?
oceans 97% of volumes
3% in fresh water
2/3 in ice
1/3 in ground
0.03% in lakes, streams, vegetations and atmosphere
what is the hydrological cycle?
water is constantly on the move
It is evaporated from the oceans, lakes, streams, the surface of the land, and plants (transpiration) by solar energy. It is moved through the atmosphere by winds and condenses to form clouds of water droplets or ice crystals.
What is the region drained by a single river variously is called a
drainage basin, watershed, river basin or catchment
What is gradient?
slope of the land it flows over
-determined by calculating the vertical drop in elevation of the channel over some horizontal distance
-meters per kilometer or feet per mile. If a river falls 1 meter per km, the slope is 1/1000 or 0.001 (0.1 percent).
what is the downstream elevation in river’s elevation?
The longitudinal profile
When do floods normally occur in the USA?
Spring
When does a river usually have steeper-sides and deeper valley?
At high elevation near headwaters
- base level is where wide floodplain is present
What happens at higher elevations?
the steeper river gradient increases flow velocity, which, in turn, increases erosional down-cutting by the river.
What does dissolve load consist of?
dissolved load consists of atoms or molecules, called ions, which are carried in chemical solution
Mandering pattern
- single-thread channel similar to the curves of a moving snake
-migrate back and forth floodplains
Braid pattern
multithread channel where there are two or more channels that unite and divide as the river flows downstream
What is a floodplain?
major river landform that develop over a period of years to decades and much longer
What is most floodplain related to?
amount and distribution of precipitation in the drainage basin, the rate at which the precipitation infiltrates (soaks) into the earth, and how quickly surface runoff from that precipitation reaches the river.
How are floods characterized?
here they occur in a drainage basin
-zones 1, 2, and 3
What is a flashflood
- most common in areas with steep topography or little vegetation, and following breaks of dams, dykes, and ice jams
- typically occur in the upper part of a drainage basin
- in zone 1
what is downstream floods of ZONE 2 associated with
inundation of the floodplain.
Zone 2 floods may cover a wide area and are usually produced by storms of long duration that saturate the soil and produce increased runoff.
Zone 3 association
particularly dangerous due to the uncertain and changing flow paths of both the river itself and ocean currents, waves and tides.
what is river discharge
int along its course is the amount of water passing through the channel cross-section at that point during a specified interval of time. River discharge is usually measured in cubic meters per second.
Why is knowledge about rivers important?
Understanding river behavior is essential for understanding the evolution of landscapes, environmental planning, and territorial planning.
What is river discharge?
River discharge is the amount of water passing through a channel cross-section at a point during a specified interval of time, usually measured in cubic meters per second.
What are some physical factors that affect river discharge?
Lithology and soil type, size and shape of the drainage basin, precipitation, and vegetation.
What are some human factors that affect river discharge?
mpermeable man-made surfaces, deforestation, and river management.
