avatar
Open Coast Issues


I wanted to share some information, thinking I stumbled on thanks to getting involved with local environmental activists and surfers. The local issue of Miyazaki Port disturbing littoral drift and road construction on sand dunes further disturbing sand budget equilibrium introduced me to the global issue coastline erosion. The 1990 debut textbook on sandy beaches gave me the basic understanding to follow the arguments against groins (Newjerseyization) and led me to a surprising discovery of India’s Madras Port (Chennai) sharing so much in common with Miyazaki. Well, the Google Satellite Photos anyway.   The port in India was built in 1875, Miyazaki’s in the 80′s. There are plans to put the same kind of groins (Tottei in Japanese) to the north of Miyazaki. Chennai (Madras?) Port’s groins to the north can be seen by zooming on the Google satellite video. They don’t seem to be helping. Some sand remains at the base, but erosion is even more extreme midway between each projection.  I gave my copy of Mike Davis’ Late Victoria Holocausts to a young Japanese activist on her way to India so I can’t verify the Madras Famine happening at around the same time as the Port Construction. Hopefully it will be easier to excersize some kind of democratic control over the coasts (and food policies) in Japan.

The book also expresses concern about global warming and coasts. So you can feel reassured that the topic didn’t just crop up so Al Gore can promote dangerous nuclear power plants. Bill McKibben and David Suzuki (I hear) have started writing about global warming 20 years ago too.

Ecology of Sandy Shores, A.C. Brown and A. McLachlan

p. 270

Managing the Littoral Active Zone

Sandy shores consist of three entities – surf zones, beaches and dunes – which are linked by the interchange of material, particularly sand. Together they comprise a single geomorphic system, termed the littoral active zone (Tinley 1985). This is part of the coast characterized by wave- and wind-driven sand transport and it lies between the outer limit of wave effects on bottom stability (usually between 5 and 15 m depth) and the landward limit of aeolian sand transport (i.e. the landward edge of the active dunes) Although this area area constitutes a single geomorphic system, ecologically it consists of two distinct systems – a marine beach/surf zone ecosystem populated by marine biota and controlled by wave energy, and a terrestrial dune system inhabited by terrestrial plants and animals and strongly influenced by wind energy. In managing sandy coastlines, it is imperative that this contrast is borne in mind.

In simple terms, managing a sandy coast means managing the sand budget and thus it is essential to understand the coupling of dune and beach systems, their exchanges of sand and their interdependence

Major structures and disturbances

Coastal engineering structures

P. 272
Komar (1983a) cites a number of interesting examples of sand erosion and shoreline changes following the construction of jetties and breakwaters. In some cases it is not immediately apparent why a particular structure has induced erosion or deposition, while in others the analysis of what has occured is straight forward adn the effects could have been predicted with some accuracy. Coastal structures built out into the water from the shore block the natural littoral drift of sand prevailing along most coasts. This deprives beaches of sand and initiates erosion in teh downdrift direction, while updrift sand deposits and the beach advances seawards.  Littoral drift is not a constant phenomenon at any given site; itvaries enormously with wave action and the direction of wave attack, and there is commonly even a reversal of drift direction under different conditions and notably during storms. The summation of all the individual sediment transport events over at least a year is the "net littoral drift" and it is this value which is important in determining the effects of coastal structures on erosion and deposition, rather than any single transport event. Among the several examples cited by Komar (1983a), the development of the Port of Madras in India is of particular interest because it was constructed on the open shore in an area of strong net littoral drift and because resulting changes have been documented since its construction was sanctioned in 1875 (Fig. 13.3).

p. 270 Despite the fact that man’s interference with his environment in general, and sandy beaches in particular, has almost invariably born unwelcome fruit, he has continued to impose changes upon the environment, partly through ignorance and an inability to learn from experience, no doubt, but also in the unshakable belief that it must
be possible to shape nature to his now needs and desires. … Dunes and other sandy areas at the top of the shore are not, in fact to be recommended for building purposes but careful research and planning can at least minimize the dangers and possible damage involved…

If management implies planning for the future, the no account of it can ignore the expected world-wide rise in mean sea level associated with the melting of polar ice as a result of the "greenhouse effect".There is no longer any doubt that this is a real problem and that it will have to be faced in the foreseeable future. Indeed some wise countries, such as Australia, are already pouring vast sums of money into research aimed at minimizing the effect of this potentialdisaster.

Leave a comment