[22, 23]. The shoreline change analysis can be automated in GIS to provide rapid,
high-resolution evaluation of multiple temporal shoreline delimitation. Two
approaches, raster-based and vector-based, are generally employed to model spatial
and temporal shoreline change. The vector approach to analyzing historic shoreline
change data contrasts with a raster approach in its sampling flexibility and temporal
scalability.
The vector approach can accept any number of temporal linear representations of
the shoreline and can flexibly sample those shorelines to calculate past variability
and project future changes. Baselines must be constructed for all historic shorelines
to provide a starting point for the transecting operation and must be digitized parallel
to the general trend of the historic shorelines. There are a number of GIS extensions
that can be used to generate transects, perform the analysis, and deliver results in GIS
format [24]. Satellite imageries in conjunction with GIS can also be used to assess
coastal storm damage. Time series of remotely sensed data have been used to
investigate sediment transport processes in the coastal areas [7, 25].
4.1.4 Water Quality Monitoring
In the area of water quality, remote sensing and GIS techniques can be used to assess
and map several water quality parameters including suspended sediments, chlorophyll, turbidity, total phosphorus, Secchi depth, temperature, and dissolved organic
matter. These water quality parameters are important in defining total maximum
daily loads (TMDLs). The remote sensing technique involves the derivation of
algorithms which relate the spectral reflectance to in situ field measurements of
water quality parameters. The exact relationship will vary regionally and depends on
the optical properties of the water. Once an algorithm is derived, the water quality
parameters for each pixel of water in the image can be calculated using only the
spectral reflectance values. GIS is usually used to present the results in
two-dimensional thematic maps and in dynamic sequential images. The GIS visualization helps to enhance understanding of water quality conditions.
Significant relationships have been shown between water quality parameters and
reflectance values from spectral wave bands or combinations of wave bands on
satellite or aircraft sensors. These algorithms are site specific, and therefore applying
the same algorithms to other sites may not be appropriate due to the very different
characteristics and compositions of column material in these waters. However, the
same procedure used to develop these algorithms may be followed to develop
algorithms for other sites. Table 5.2 lists some of the algorithms that have been
derived from remote sensing data. The sources for these algorithms are also provided
in the table.
Suspended sediments increase the radiance emergent from surface waters in the
visible and near-infrared proportion of the electromagnetic spectrum [31]. The
amount of reflected radiance tends to saturate as suspended sediment concentrations
increase [32–34]. The point of saturation depends on wavelength with the shorter
wavelength saturating at low concentrations. Since suspended sediments increase
5 Geographic Information Systems and Remote Sensing Applications in Environmental. . . 209
high-resolution evaluation of multiple temporal shoreline delimitation. Two
approaches, raster-based and vector-based, are generally employed to model spatial
and temporal shoreline change. The vector approach to analyzing historic shoreline
change data contrasts with a raster approach in its sampling flexibility and temporal
scalability.
The vector approach can accept any number of temporal linear representations of
the shoreline and can flexibly sample those shorelines to calculate past variability
and project future changes. Baselines must be constructed for all historic shorelines
to provide a starting point for the transecting operation and must be digitized parallel
to the general trend of the historic shorelines. There are a number of GIS extensions
that can be used to generate transects, perform the analysis, and deliver results in GIS
format [24]. Satellite imageries in conjunction with GIS can also be used to assess
coastal storm damage. Time series of remotely sensed data have been used to
investigate sediment transport processes in the coastal areas [7, 25].
4.1.4 Water Quality Monitoring
In the area of water quality, remote sensing and GIS techniques can be used to assess
and map several water quality parameters including suspended sediments, chlorophyll, turbidity, total phosphorus, Secchi depth, temperature, and dissolved organic
matter. These water quality parameters are important in defining total maximum
daily loads (TMDLs). The remote sensing technique involves the derivation of
algorithms which relate the spectral reflectance to in situ field measurements of
water quality parameters. The exact relationship will vary regionally and depends on
the optical properties of the water. Once an algorithm is derived, the water quality
parameters for each pixel of water in the image can be calculated using only the
spectral reflectance values. GIS is usually used to present the results in
two-dimensional thematic maps and in dynamic sequential images. The GIS visualization helps to enhance understanding of water quality conditions.
Significant relationships have been shown between water quality parameters and
reflectance values from spectral wave bands or combinations of wave bands on
satellite or aircraft sensors. These algorithms are site specific, and therefore applying
the same algorithms to other sites may not be appropriate due to the very different
characteristics and compositions of column material in these waters. However, the
same procedure used to develop these algorithms may be followed to develop
algorithms for other sites. Table 5.2 lists some of the algorithms that have been
derived from remote sensing data. The sources for these algorithms are also provided
in the table.
Suspended sediments increase the radiance emergent from surface waters in the
visible and near-infrared proportion of the electromagnetic spectrum [31]. The
amount of reflected radiance tends to saturate as suspended sediment concentrations
increase [32–34]. The point of saturation depends on wavelength with the shorter
wavelength saturating at low concentrations. Since suspended sediments increase
5 Geographic Information Systems and Remote Sensing Applications in Environmental. . . 209