Streams and Flooding

The hydrologic cycle is the cycle through which water in the hydrosphere moves.

Main reservoirs are oceans, clouds (atmosphere), glaciers, ground water and lakes and streams; greatest fluxes are from the ocean to the atmosphere

Residence time

Residence time = size of reservoir / rate of influx- average time of water molecule to exist in the ocean and then go back into condensation is 34 years

Largest reservoir of water on earth is oceans

Largest of unfrozen freshwater is ground water

A stream is flowing water in a channel

A drainage basin is the region in which surface water drains into a particular stream

A discharge is the amount (volume) of water flowing past a given point over a particular time interval

Cubic feet per second (CFS) Q=VA – q is discharge v is velocity a is area

Alluvium is general term for particulate stream sediment

The main factor in determining how much sediment a stream can carry is stream capacityThis depends on discharge and amount of sediment available

Hydraulic Action: the friction of moving water loosens rock fragments and soil from the sides and base of the stream channelAbrasion: the grinding of sediment particles that wares them down and enlarges the stream channelDissolution: chemical attack on minerals in sediments and stream channel- places ions in solution

The gradient of a stream is the slope of a stream channel

The gradient near the source It is usually a steeper slope and as the stream continues on it gets less steep and carries smaller sediment