Environmental and resource applications
The spatial distribution of any of the calculated parameters can immediately
be visualized within the GIS. Figure 8 illustrates the spatial distribution
of the calculated average sediment turnover as described below. The
highest turnover is occurring in the foreshore and lowest values occurring
in the deeper zones. Some local modifications can be observed, e.g. the
increase of sediment turnover in areas of moving ridges in the central
parts of the illustration. Beside morphological changes, the influence of
incorrect sea survey data is obvious in this illustration. The identification
of incorrect data has to be improved.
Examples for statistical parameters
Changes of depth and mass balances are not the only parameters to
describe morphological changes and activities. The use of a GIS enables
one to determine a variety of more accurate parameters in a very effective
way. Some of these parameters are discussed in this chapter.
Sediment turnover
The sediment turnover in a grid cell can be defined as the change in
the shoreface elevation between all survey campaigns. It is a measure
for the morphological activity m an area (Hofstede, 1991). Sediment turnover is influenced by the number of surveys and the time between
consecutive survey campaigns. Calculation of the average sediment
turnover per survey (i.e. sediment turnover divided by the number of
surveys) for every grid cell leads to more accurate description of the
morphological activity.
Sediment balance
The sediment balance for a grid cell or any other area is he clifference
in volume between the oldest and youngest survey campaigns. Incorrect
survey data has a significant influence on sediment balance. Therefore,
only limited conclusions can be drawn from the results of sediment
balance calculations.
Sediment balance - Sediment turnover ratio
The ratio of sediment balance and secliment turnover ranges from 0 to
± 1.0. By definition, sediment balance cannot be larger than sediment
turnover. When the ratio is close to unity, all changes in elevation over
time take the same direction, i.e. in the corresponding grid cells either
only erosion or only accumulation occurs over time. Values close to zero
indicate that erosion and accumulation alternate. However, similar to
sediment balance the balance-turnover ratio is influenced considerably
by inaccurate survey data.
Regression (in-or decrease) of shoreface elevation per year,
correlation coefficient
From a time series of shoreface elevation, a trend can be calculated.
The trend is described by two parameters: the gradient and the coefficient of the determination, r
2 . The gradient expresses the velocity of
229
The spatial distribution of any of the calculated parameters can immediately
be visualized within the GIS. Figure 8 illustrates the spatial distribution
of the calculated average sediment turnover as described below. The
highest turnover is occurring in the foreshore and lowest values occurring
in the deeper zones. Some local modifications can be observed, e.g. the
increase of sediment turnover in areas of moving ridges in the central
parts of the illustration. Beside morphological changes, the influence of
incorrect sea survey data is obvious in this illustration. The identification
of incorrect data has to be improved.
Examples for statistical parameters
Changes of depth and mass balances are not the only parameters to
describe morphological changes and activities. The use of a GIS enables
one to determine a variety of more accurate parameters in a very effective
way. Some of these parameters are discussed in this chapter.
Sediment turnover
The sediment turnover in a grid cell can be defined as the change in
the shoreface elevation between all survey campaigns. It is a measure
for the morphological activity m an area (Hofstede, 1991). Sediment turnover is influenced by the number of surveys and the time between
consecutive survey campaigns. Calculation of the average sediment
turnover per survey (i.e. sediment turnover divided by the number of
surveys) for every grid cell leads to more accurate description of the
morphological activity.
Sediment balance
The sediment balance for a grid cell or any other area is he clifference
in volume between the oldest and youngest survey campaigns. Incorrect
survey data has a significant influence on sediment balance. Therefore,
only limited conclusions can be drawn from the results of sediment
balance calculations.
Sediment balance - Sediment turnover ratio
The ratio of sediment balance and secliment turnover ranges from 0 to
± 1.0. By definition, sediment balance cannot be larger than sediment
turnover. When the ratio is close to unity, all changes in elevation over
time take the same direction, i.e. in the corresponding grid cells either
only erosion or only accumulation occurs over time. Values close to zero
indicate that erosion and accumulation alternate. However, similar to
sediment balance the balance-turnover ratio is influenced considerably
by inaccurate survey data.
Regression (in-or decrease) of shoreface elevation per year,
correlation coefficient
From a time series of shoreface elevation, a trend can be calculated.
The trend is described by two parameters: the gradient and the coefficient of the determination, r
2 . The gradient expresses the velocity of
229