LE8 - STREAMS AND FLOODING Flashcards
The basic role of streams and rivers
To drain water off the landscape and to transport sediments
A stream may overflow its banks when its ability to carry water is overwhelmed by the sheer volume of water flowing off the landscape and create
Flood
Humans tend to concentrate their settlements along waterwats plus relatively frequent nature of flooding puts large number of people and buildings at
Risk
Historically, people take Advantages of living along rivers, why?
Water supply, fertile soils, and ability to transport goods
Described as the voume of water moving through a channel over a given time interval, commonly measured in units such as cubic feet per sec. Ft³/s
Stream discharge
Process where water flows through stream channels
Runoff
Precipitation reaching the land surface moves downslope in tuin sheets
Overland flow
Allows water to return back to the atmosphere
Evaporation and plant transpiration
Discharge of groundwater into the surface environment
Groundwater basèflow
Groundwater may travel anywhere from a few days to thousand of years before discharging into a stream channel
Sporadic input of water to a stream
Process of Stream Discharge
Precipitation that falls onto land surface can take different paths through the hydrologic cycle, some of the water moves overland dlow and enters directly into stream channeos, most of the remaining water infiltrates the soil zone where it can return to the atmosphere via evaporation and plant transpiration. If soil moisture becomes great enough, infiltrating water can reach the water table and eventually flow with the grounwater system and discharge into the stream channel.
Provides information about river or stream by simple plottinf the discharge by time
Stream hydrographs
amount of time for water to move across the landscape and into the channells
lag time
lag time varies depending on the
distance between where the rain is falling and the particular channel where discharge is being measured
continuous input of groumdwater baseflow allows streams in many areas to keep flowing at some minimum level called…
baseflow conditions
groundwater baseflow keeps streams from…. is also critical in maintaining the health of stream ecosystems
going dry between rain events
high precipitation allows more water to infiltrate to the water table which causes the water table in humid regions to be higher than the stream channel, forcing groundwater to ________________ also called as _______.
flow into streams, gaining streams
high precipitation allows more water to infiltrate to the water table which causes the water table in humid regions to be higher than the stream channel, forcing groundwater to ________________ also called as _______.
flow into streams, gaining streams
____ result of less deep infiltration in arid areas resulting in a water table that is below the level of most stream channels, where the water in the stream will _____
losing streams, flow into the groundwater system
stream hydrographs are useful because?
it helps analyze how stream discharge change overtime
overland flow from heavy rains creates ____ in discharge, which can be large enough to cause streams to overflow their banks and flood low-lying areas.
spike
water that infiltrates and slowly makes its way to a stream through the groundwater systems provides a steady supply of water called_____
baseflow
groundwater baseflow enables stream to ____ between precipitation events
keep flowing
a network of stream channel where merging tributaries form progressively larger streams
drainage system
often applied to the larger stream that serves as the principal channel within a drainage system.
river
the upper portion of the river is called ____ usually small and relatively fast moving occupy narrow valleys, and ________ is the lower part of the system where a river empties to an ocean, lake or another river which are gently flowing that occupy wider valleys.
headwater; mouth
individual systems are separated from one another by a tp[pgraphic high or crest in the landscape called a …
drainage divide
