# Characteristic Numbers of Current Velocity (independent of tides)

### From BAWiki

## Motivation

Calculation and graphic display of several tide-independent characteristic numbers of current velocity can yield additional insight into velocity related phenomena of natural coastal and/or inland waters. In contrast to the computation of the tidal characteristic numbers of salinity the tide-independent numbers can be preferable used for

- natural waters which are not dominated by the tides, e.g. like the coastal waters and estuaries along the Baltic Sea coast of Germany, or in
- determination of characteristic values of current velocity for an arbitrary long (or short) period of time, or in
- those parts of tidal waters, where either no or only short current reversals occur, which makes the computation of tidal characteristic numbers of current velocity neither meaningful or not even possible.

In particular there are several useful applications possible for this type of data analysis, for example:

- From the computed times or frequencies for the duration of high current velocity and the duration of low current velocity one can draw conclusions with respect to the impact of current velocity on organisms living in the water or along the beaches.

**Analysis of Characteristic Numbers of Current Velocity Data is carried through by the computer programs LZKVF and NCANALYSE.**

## Definitions for the Characteristic Numbers

#### Maximum Current Velocity (Vmax)

Highest (local) value of current velocity within the period of data analysis.

Example figures: maximum current velocity.

Data analysis: LZKVF and NCANALYSE.

### Maximum valid Current Velocity (xVmax)

Highest valid (local) value of current velocity within an arbitrary period of time, computed out of a time serie which may contain invalid data due to different reasons (drying, instrument failure, etc.).

Data analysis: NCANALYSE.

#### Residual Current Velocity (Vres)

Residual value of current velocity (computed from addition of vectors) within the period of data analysis.

The residual is computed based on the real duration of flooding (wet period) for each location.

Example figures: residual current velocity.

Data analysis: NCANALYSE.

#### Mean Magnitude of Current Velocity (VmitB)

Mean magnitude of current velocity within the period of data analysis.

Mean current velocity is computed based on the real duration of flooding (wet period) for each location.

Example figures: mean magnitude of current velocity.

Data analysis: LZKVF and NCANALYSE.

#### Standard Deviation of Current Velocity (StdAbw)

Standard deviation of current velocity within the period of data analysis.

Computed for permanently flooded areas only.

Example figures: standard deviation of current velocity.

Data analysis: NCANALYSE.

#### Variance of Current Velocity (Var)

Variance of current velocity within the period of data analysis.

Computed for permanently flooded areas only.

Example figures: variance of current velocity.

Data analysis: NCANALYSE.

#### Duration of High Current Velocity (VhDau)

Period of the time during which local current velocity lies above a given velocity limit.

Example figures: duration of high current velocity.

Data analysis: LZKVF and NCANALYSE.

#### Duration of Low Current Velocity (VnDau)

Period of the time during which local current velocity lies below a given velocity limit.

Example figures: duration of low current velocity.

Data analysis: LZKVF and NCANALYSE.

#### Relative Frequency Distribution of Current Velocity (RelFreq)

Relative frequency of current velocity within given velocity intervals.

Example figures: relative frequency distribution of current velocity.

Data analysis: LZKVF and NCANALYSE.

#### Cumulative Frequency Distribution of Current Velocity (CumFreq)

Cumulative frequency of current velocity within given velocity intervals.

Example figures: cumulative frequency distribution of current velocity.

Data analysis: NCANALYSE.

#### Exceedance Frequency of Velocity Limits (ExcFreq)

Exceedance frequency of velocity limits within the period of data analysis.

Example figures: exceedance frequency of velocity limits.

Data analysis: NCANALYSE.

#### Underflow Frequency of Velocity Limits (UndFreq)

Underflow frequency of velocity limits within the period of data analysis.

Example figures: underflow frequency of velocity limits.

Data analysis: NCANALYSE.

### Quantiles of Current Velocity

Current velocity value of a time series which is not exceeded of a certain percentage of present current velocity values.

Computed for permanently flooded areas only.

- a) Example figures: median of current velocity Q_0.50
- b) Example figures: quantiles of current velocity Q 0.01, Q 0.05, Q 0.95, Q 0.99

Data analysis: NCANALYSE.

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