With regard to the sea-bed survey it can be stated that before obtaining the sand the presence and position of the borrow areas for this material should be found through bathymetric and & seismic reflection survey, grid positioning, gravity cores, vibrocores, cone penetration tests, boreholes & sampling (preferably undisturbed samples), etc.
Through laboratory tests the characteristics of the sand to be used must be determined, a.o. average grain size, grain size distribution, mineralogical type, specific density. Attention should also be paid to silt and clay particles.
The various dredging techniques should be compared and the right one should be chosen. In some cases adaptation is necessary in order to achieve environmental friendly dredging. Deep dredging in restricted areas or the use of larger but thinner subsurface layers and limited depths, dredging in alternate zones, specially designed suction heads and pumping systems, silt screens, etc., are aspects which can be considered. In some cases deep dredging for sand can be followed by environmental friendly storage of contaminated sediments and certain wastes in the created sand borrow pits. In some cases prior to extraction of suitable sand, layers of marine mud and clay have to be removed.
Of importance is the distance between the marine borrow areas and the land reclamation under consideration. When the distance is too short the new flexible dynamic equilibrium coast can not be obtained, because the slope towards the sea-bed of the new coast is influenced; when the distance is too large the costs become too high; environmental factors and geological uncertainties can also play a role. Generally there is an optimum range, provided suitable borrow areas can be found within that range.
Even if a new flexible dynamic equilibrium coast cannot be achieved, because erosion is clearly dominating accretion, and solid seawall elements therefore have to be chosen for coastal protection, sand from the sea-bed still has to be used for the land reclamation, which means that dredging remains in all cases of vital importance.
Very important, also from a viewpoint of nature, planning and cost effectiveness, is that a coastal extension or offshore island of certain dimensions can be created segment after segment, phase after phase.
Finally, with regard to the urban and regional planning of the newly acquired area, landscaping and the introduction of parks and even of new nature reserve areas - provided that the new area is not too small - offer excellent possibilities. For a relative high value of a nature reserve area it is important to obtain an abundance of different species. This can be achieved by applying differences in height, in gradients from salt to fresh water, differences in chalk content, variations in micro-climate, etc.
Of great importance in the terrestrial coastal zone is water resources management and linked to that the reduction of waste loads in the adjacent sea, bay, estuary or lagoon.
Therefore special attention is necessary for sewer systems; waste water purification; the collection-transport-temporary disposal-processing-recycling & final environmental friendly storage of solid wastes.
In the coastal zone we always have to deal with existing and new man-induced conversion processes in the field of industry, power stations for energy-supply, agriculture and acquaculture, transport and distribution, and also in the domestic sector.
In the direct future those processes should be developed and implemented that with less raw materials and with less energy, produce products at a higher yield, with less hazardous emissions to air, water and soil, and with less waste products. In case waste products are formed, they should be converted to environmental friendly products, or safely stored.
