# Tidal Characteristic Numbers of Morphodynamics

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##### Revision as of 11:00, 9 June 2010 by imported>BAWiki 3

## Motivation

Computation as well as graphical display of the tidal characteristic numbers of morphodynamics contribute to a better understanding of short term system behaviour of tidal estuaries and coastal seas. Morphological variability within a tidal cycle or over a spring neap cycle can be assessed.

- Maximum, mean and minimum depth during one or several tidal cycles provide the setting, within which morphological changes can take place. Especially minimum depth values are of great interest for many navigational purposes.
- Tidal depth variation is ideal to describe morphological variability within a tidal cycle. Contrary, tidal depth change is well suited to characterise the respective integral depth change. The magnitude of tidal depth change is always less or equal to the respective tidal depth variation.
- The characteristic numbers for tidal erosion, tidal deposition as well as an additional dimensionless number help to clarify the significance of erosive as well as depositional processes at the bottom. Even when tidal depth variation and tidal depth changes are small, erosion as well as (compensating) deposition may still be strong and therefore relevant processes.

An automatic analysis of all tidal characteristic numbers of morphodynamics is carried through by the computer program TDKWF.

## Definition of the Tidal Characteristic Numbers of Morphodynamics

### Maximum Tidal Depth

Greatest depth between two subsequent low waters.

Example: Not yet available.

### Minimum Tidal Depth

Smallest depth between two subsequent low waters.

Example: Not yet available.

### Mean Tidal Depth

Mean depth between two subsequent low waters.

Example: Not yet available.

### Tidal Depth Variation

Magnitude for the difference of maximum tidal depth and minimum tidal depth between two subsequent low waters.

Example: Not yet available.

### Tidal Depth Change

Difference between actual depth at the end and the beginning of a tidal cycle between by two subsequent low waters.

Example: Not yet available.

### Tidal Erosion

Sum of all depth increments (deepening) within a tidal cycle, defined by two subsequent low waters.

Example: Not yet available.

### Tidal Deposition

Sum of all depth decrements (shallowing) within a tidal cycle, defined by two subsequent low waters.

Example: Not yet available.

### Tidal Deposition/Tidal Erosion

Dimensionless number. Describes the relative significance of tidal deposition versus tidal erosion within a tidal cycle. Positive numbers indicate net deposition, whereas negative numbers indicate net erosion. A value of 1.0 corresponds to deposition with no erosion, whereas a value of -1.0 is equivalent to erosion with no deposition. Ín case of equilibrium between deposition and erosion the characteristic number will be 0.0. A tidal cycle is defined by two subsequent low waters.

Example: Not yet available.

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