Hydrology Terminology

Watershed

Streamflow

Routing

Reservoirs

Channel

Precipitation

Snow

Runoff

Infiltration

Unit hydrograph

Timing

Flooding

Flow

Grade lines

Land Use

Frequency

-return period

-probability

• The frequency of a storm event is described by its return period. For example a two year storm event has a 1 in 2 chance of occurring in any given year.

• The probability is also affected by the return period. Thus the probability of a 2 year storm occurring is 50%. The probability of a 100-year event occurring is 1/100 or 1%

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