Rivers and Flooding

Hydrosphere

The way water moves through the Earths System

Precipitation

Liquid water or solid ice falling back to Earth

runoff

water flowing off the surface of land to form streams

Infiltration

Water soaking into the ground

interception

water retained by plants or human made structures

drainage basin

a large geographic area that funnels water into a main stream channel

drainage basin (watershed/catchment)

a large geographic area that funnels water into a main stream channel

drainage divide

a ridge of local higher relief that separates adjacent drainage basins

longitudinal profile

Traces a rivers elevation. It is steepest at higher elevations (headwaters) and shallowest near base level (mouth)

Gradient

The rise over run (elevation divided by distance traveled). It is the slope of the river.

Total load

The full amount of sediment a stream carries, composed of bed load, suspended load and dissolved load

Bed load

Sand and gravel that moves along the stream bed by saltation

suspended load

clay and silt particles carried above the bed by flowing water making the river appear murky

dissolved load

soluble ions from minerals (and pollutants) that are invisible and carried as an aqueous solution.

meanders

Curving channel bends. Velocity is greater on the outside of curves (causing erosion/cutbank) and slower on the inside (causing deposition/point bar)

floodplain

a broad valley created from overbank flow hat deposits sedimenr over multiple flood events.

delta

a depositional feature formed where a river meets a larger body of water (ocean or lake). Occurs in zone 3 (deposition) because the stream flow widens and slows, dropping sediment.

flooding

a natural process of overbank flow that occurs when discharge is greater than the channel capacity

stage

The height of the water level in a channel

bankfull stage

the height of a river above which water will spill over its banks

flood stage

the height at which the river is already overflowing its banks and is impacting the floodplain

discharge

the volume of water per unit time flowing through a certain spot of the river. Q= Velocity x Area

Hydrograph

A graph showing stream characteristics versus time

rating curve

a graph that relates historical discharge values to recorded stage (gage height)

Lag time

The time discrepancy between peak precipitation and peak discharge

Recurrence Interval (T)

The average number of years between floods of a given magnitude

Flood probability

The per year chance of a flood of a certain magnitude occurring calculated as 1/T or Recurrence Interval

sinuosity

the length of a stream channel divided by the straight line distance between its ends.

levee

a natural or human built embankment along the sides of a stream channel

braided stream

an overloaded stream so full of sediment that water flow is forced to divide and recombine in a braided pattern.