PROCEEDINGS

FIRST INTERNATIONAL CONFERENCE ON

“SOFT SHORE PROTECTION”

Global warming, polar cap melting, sea level rising and wave-current action intensifying, factors responsible for alarming phenomena of coastal erosion, on one hand, and adverse environmental impacts and high cost of “hard” protection schemes, on the other, have created interest to examine in detail the potential and range of applicability of the immerging and promising category of “soft” shore protection methods against such erosion. “Soft” methods, e.g. beach nourishment, submerged breakwaters, artificial reefs, gravity drain systems, floating breakwaters, plantations of hydrophyle shrubs or even dry branches, etc, applied mostly during the past 20 years, are recognised to possess technically, environmentally and financially advantageous properties deserving more attention and further developmental experimentation than has been given hitherto.

“Hard” shore protection methods, such as seawalls, groins and detached breakwaters, on the other hand, artifacts borrowed from port design and construction technology, no matter how well designed and implemented they may be, can hardly avoid fortification of the concomitant erosive, often devastating, effect on the down-drift shores, and anyway do not constitute an environmentally and financially attractive solution to be applied to long stretches of eroding shoreline. Engineers and scientists practising design and implementation of shore defending schemes are, for a few years now, aware of the public and private demand for improved shore protection technologies and encourage efforts that promise enrichment of the log of environmentally sound and financially attractive methods that can be safely applied.

The objectives of the First International Conference on “Soft Shore Protection” held between 18 and 22 October 2000, in Patras, Greece, the Proceedings of which are reported in this volume, was to offer the opportunity to scientists and engineers to present their ideas, work, experiments and results and at the same alert the international community in intensifying and/or sponsoring research and pilot in situ experiments on promising methods of the “soft” protection category.

The concept of “soft” intervention, or “resilience” to sea wave-current action requires clarification, both for specialists and the general public. Sea action, a natural and unviolable phenomenon, when exceeding certain level, develops the capability to transport the sediment of the seabed, by either lifting grains (suspended matter) or displacing in small steps the bedload. The sediment transport mechanism in the surf zone is operating through either the “longshore” water current motion, driven by wave action and other causes, or the “rip” currents produced by the water setup during wave activity. Suspended matter, distributed within the entire moving water body is left out from the discussion that follows due to the complexity or inability to be controlled.

Any arrangement capable to reduce the speed or modify the direction of motion of longshore or rip currents and thus reduce or eliminate their sediment transport capability, is a shore protection arrangement. Breakwaters, groins, jetties, and piers have this property and hence are correctly classified as shore protection arrangements. The fact that they are “borrowed” from port construction technology is not a disadvantage per se, since cost/effectiveness and environmental acceptability constitute the criteria of suitability for application.

Responsible for bedload transport is not all the water body participating in the longshore or rip current motion. Only a very thin layer of water, of thickness not exceeding 0.5 cm, moving immediately above the seabed and transferring to the seabed constituents part of its kinetic energy, is the agent of sediment transport and the related erosion. Hence of prime concern of shore protection arrangements is nutralization of the operation of this water layer. Interception of the total of wave-current energy is unnecessary as well as harmful. Indeed, intercepting and absorbing wave and current energy of water that does not erode a shore implies elimination of the benevolent function of natural pollutant recycling performed by the sea. It turns out, in fact, that interception and absorption of all sea water energy is an anti-environmental act and as such, should be prohibited altogether.

The broader definition of “soft” protection arrangements is, hence, the interception and/or cut-off and/or divert and/or eliminate generation of water current motion in the thin erosive water layer acting upon bedload. Depending upon the requirement of the arrangement, e.g. its stability, integrity, functionality, etc, the layer of water whose energy is allowed to be intercepted can be several times the size of the energy transfer layer, paying attention to the need for minimal intervention in the water motion.

As already mentioned, drainage systems using pumps or gravity to eliminate setup during wave storms, aims at eliminating rip currents at their generation cause. Longshore currents are not intercepted at all and such arrangements are soft. Floating breakwaters, while eliminating wave action and hence intensification of longshore currents and generation of water setup and rip currents, are also soft. Detached low-height above seabed breakwaters and low-height groins are obviously soft arrangements. Last, but important soft interventions are these of nourishment, a practice deserving general attention on account of their generic character.

Identification of soft protection methods and evaluation of their quality (effectiveness, environmental impacts, cost, etc) was left to the authors and now to the good judgment of the reader. This is the first collection of technical information on soft shore protection and hence whatever criteria of quality classification has to rely on work that will follow and not on “borrowed” experience.

“Hard” protection advocates will find understanding listeners of their criticism. Soft shore protection is only starting to develop and certainly needs their input experience in their development course during the next fifty or so years towards its maturity. Such advocates, now under the attack of governments and supreme courts of many countries, may find a good ally in soft protection and also wisdom in the phrase "Man masters nature not by force but by understanding" of Jacob Bronowski (1908-74).