50
4 Hydrology of (Shallow) Coastal Regions
Condensation
Evaporation
Runoff
Precipitation
Atmospheric transport
Temporal storage
Fig. 4.1 Schematic water cycle of humid coastal areas. Precipitation exceeds evapotranspiration on
the land side, resulting in a positive water balance. Excess water flows toward the sea
Shallow coastal regions mostly are also characterized by a flat terrain. A flat terrain favors
slow hydrological flow processes compared to quick flow processes, for example, related
to runoff generation. Usually, in flat terrain subsurface flow processes are more important than surface runoff, except in case of soil saturation. Then, water accumulates at the
surface and may generate surface runoff.
In addition to the topography, dominance of hydrological processes also depends on
the soil properties and on the soil composition of coastal regions. While fine-textured
soil material tends to a better storage behavior, coarse-textured soils have a higher water
permeability. Storage capacity and permeability directly have an impact on the runoff
generation processes.
Figure 4.2 shows the spatial distribution of the permeability at the Northwest German
North Sea Coast.
1 Large parts of the shallow coastal areas are dominated by soils with
a low permeability. The fine-textured marsh soils mainly consist of clay, silt and organic
matter. They are characterized by a low permeability and a high productivity. For agricultural (or any other anthropogenic) use they require an intense drainage (see the dense
drainage network in Fig. 4.2).
The implications of these delineated hydrological characteristics for the water management of coastal regions are as follows (see also Figs. 1.3 and 1.4):
• Humid coastal regions are characterized by a positive water balance. If these regions
shall be used for agriculture or settlements, the area needs to be drained, and the drained
water needs to be conveyed to the sea,
• Shallow coastal regions are characterized by a flat terrain. Therefore, hydraulic gradients are small, and undrained coastal regions are usually wet landscapes. Efficient
drainage of such regions requires methodologies to accelerate water flow in order to
keep the regions dry.
1
k f is the coefficient of permeability or hydraulic conductivity; data has been provided by the Lower
Saxonian Agency for Mining, Energy and Geology.
4 Hydrology of (Shallow) Coastal Regions
Condensation
Evaporation
Runoff
Precipitation
Atmospheric transport
Temporal storage
Fig. 4.1 Schematic water cycle of humid coastal areas. Precipitation exceeds evapotranspiration on
the land side, resulting in a positive water balance. Excess water flows toward the sea
Shallow coastal regions mostly are also characterized by a flat terrain. A flat terrain favors
slow hydrological flow processes compared to quick flow processes, for example, related
to runoff generation. Usually, in flat terrain subsurface flow processes are more important than surface runoff, except in case of soil saturation. Then, water accumulates at the
surface and may generate surface runoff.
In addition to the topography, dominance of hydrological processes also depends on
the soil properties and on the soil composition of coastal regions. While fine-textured
soil material tends to a better storage behavior, coarse-textured soils have a higher water
permeability. Storage capacity and permeability directly have an impact on the runoff
generation processes.
Figure 4.2 shows the spatial distribution of the permeability at the Northwest German
North Sea Coast.
1 Large parts of the shallow coastal areas are dominated by soils with
a low permeability. The fine-textured marsh soils mainly consist of clay, silt and organic
matter. They are characterized by a low permeability and a high productivity. For agricultural (or any other anthropogenic) use they require an intense drainage (see the dense
drainage network in Fig. 4.2).
The implications of these delineated hydrological characteristics for the water management of coastal regions are as follows (see also Figs. 1.3 and 1.4):
• Humid coastal regions are characterized by a positive water balance. If these regions
shall be used for agriculture or settlements, the area needs to be drained, and the drained
water needs to be conveyed to the sea,
• Shallow coastal regions are characterized by a flat terrain. Therefore, hydraulic gradients are small, and undrained coastal regions are usually wet landscapes. Efficient
drainage of such regions requires methodologies to accelerate water flow in order to
keep the regions dry.
1
k f is the coefficient of permeability or hydraulic conductivity; data has been provided by the Lower
Saxonian Agency for Mining, Energy and Geology.