( Illtem. J. ElIl'irolllllelltal Studin, 199R. Vol. 55, pp.I~23 1998 OPA (Overseas Publishers Association) N. V. Reprints available directly from the publisher Published by license under Photocopying permitted by license only the Gordon and Breach Science Publishers imprint. Printed in India. ) i j I TO FEED OR NOT TO FEED, THAT IS OFTEN THE QUESTION R. H. CHARLIERa.b.C, D. DECROOa, C. P. DE MEYER a.c and B. LAHOUSSEa "HAECON, Deinsesteenweg 110, B-9031 Dronqen (Cent): bUniversity of Brussels (VUB): CInt. Fundamental and Applied Quaternary Ceolo?}y Course ( Receil'ed in final form 2 J F ehruary J997 ) Restoring beaches and stabilizing coastlines by the "soft method", viz. replacing eroded sand by artificial nourishment, is an approach that has now been practiced in several locations around the world for some time. It is often claimed as a "first" by California and by New York (Coney Island 1922). Half a decade ago the largest such operation could be claimed by Belgium (Knokke-Heist 1989). Some of these programs continue today as a result of monitoring and maintenance. Successful or not, the technique remains subject to strong critique and is labeled by some as the building of sand castles awaiting to be wiped out by the next storm. In the US there are accusations of subsidizing shorefront property owners. This is not a valid argument in most countries because the State owns the shorefront. Recently the Commission of Engineering and Technical Systems of the (US) National Research Council recognized artificial nourishment as a viable protection and restoration method. It is, of course, not equally valid for all sites. Furthermore profile nourishment, rather than beach reconstruction has been advocated for some time. The recent experien- ces in Belgium (Westhoek. Ostend, De Haan), where storms of exceptional fury lashed at "restored" beaches, seem to buttress the confidence manifested in the approach. This paper reports on the most recent observations along that sector of the North Sea coast. Keywords: Coastal protection; sediment transport; beach nourishment; perched beach INTRODUCTION Artificial nourishment remains a controversial approach to counter shoreline erosion and to restore depleted beaches. Yet, it has been carried out, apparently with notable success. Earliest beach nourish- ment projects were launched in California (1919) and on Coney Island 2 R. H. CHARLIER et al. (New York, 1929). A comparison of effects and methods of "hard" and "soft" protection has been published some time ago by the authors of this paper [1]. Since then the practice of profile feeding, calling for a feeder berm, has been tested and seems to provide a still better approach [2]. Opposition to artificial nourishment is frequently based on the view- point that it is subsidizing shorefront property owners and can best be likened to building sand castles awaiting to be wiped out by the next storm. The argument is not applicable in most countries of the world, because in opposition with the situation in the United States, else- where the State, and not private owners, owns the shorefront. Nourishment projects span the entire world. A random selection of examples includes the interventions of the US Army Corps of Eng- ineers in Florida. In Georgia (USA) a combination of hard and soft counter-erosion measures were taken. Tybee Island has a history of shifting shorelines and severe coastal erosion [3]. Groins, seawalls and revetments have been built over the years, howcver, more recently, beach nourishment was carried out as an alternative and complemen- tary approach. Beach nourishment was also carried out further south at Hallandale, Florida. The project was the subject of a thorough ecological impact study which showed that seven years after the oper- ation had been completed no ill effects on fish life could be evidenced. Other sites for which beach nourishment has been rccommended as a deterrent for coastal erosion are Amanohashidate Beach [4J in Japan and Folly Beach in South Carolina [5]. In the lattcr location beach nourishment over a distance of 5140 m involving over 522, 000 m3 of material is proposed to restore 9 1/2 ha of beach. The feasibility study points to following impacts: temporary disturbance of the ben- thos, increase in water turbidity, decline of aesthetic values, increase in automobile emissions and in noise levels. All are however tempo- rary. In Australia and New Zealand there are several examples of severe beach erosion. At Balaena Beach, Wellington, New Zealand, the beach required protective action and restoration [6]. The choice was made to artificially rebuild the beach, in 1981-1982, using dredged sandy granular gravel. The beach was monitored between 1982 and 1984. Notwithstanding considerable sediment mobility in response to locally TO FEED generated wind waves, nearly all the nourished material was retained in the littoral zone. Decisions must be urgently taken in Kenya, where such beaches as Malinai, Watamu, Tiwi, Diani, to name but these are in critical condi- tion and dire economic conditions have become a serious problem. Across the continent the situation is as dramatic along the Gulf of Guinea (e.g. Ivory Coast) and on the Niger Delta. The prognosis is no less worrisome in North Sinai or the Bay of Bengal. Years ago Rio de Janeiro's Copacabana and Cannes' La Croisette fashionable beaches were thus rebuilt. More recently restoration measures were taken in Italy and Great Britain. An extensive bibliography has been included in a recent publication of the authors [7]. In the seventies Belgium undertook the largest beach nourishment project in the world at Knokke (Fig. 1) [8]. Other nearly as sizable projects have been carried out since elsewhere, e.g. in the United States and the United Kingdom has since applied the method along its North Sea Coast wherever feasible. The works proved to have performed well during the fierce 1996 storms. The paper briefly reviews the experiences and it answers some questions recently raised in connection with the De Haan (Le Coq) project. ( 8"...,.. oWAlCHfRfN ".. S ,,'- ~~INGS av}>- ) LfKKERBEK ~ <vi;; HflsrZOOT£ -<--'V~ it \, IX lEEBRUOG ~o" ---, <v OK~,QKKE <v2J~ ~~~,i ~ " \ s , -~ VOSSESLAG 'OfHAAH --' ""~' ..' ~ OST~~~OEHE.BRWG'Gf':" '-, ~'<'- L >Jl)'-/ 0'" 11\'11.. ~ ~'fUWPOORT Of PANN \) ~ KOKSIJdE""°" \ \..G "" : ~. <v OUNKERQUE; ~ 6 DUNKIRK' . ~.+ ~JS 0 /(~ ./ Ct:. ,'> ~ ; P. f R 'Jv.( / ~ )\-.~" / ( ~ .1IlLE J. TOURNAI FIGURE 1 Location Map Belgian North Sea Coast (Charlier). 4 R. H. CHARLIER et al. WEST COAST OF BELGIUM 1. De Panne The design of coastal protection works in the French/Belgian border area was carried out from 1994 through 1996. Like further east, the North Sea coast between the French town of Dunkirk (Dunkerque) and the Belgian sea resort of De Panne is made up of sandy beaches and dunes. The foreshore suffers from erosion and dunes are also damaged during storm periods. In the framework of the Interregional program financed by the European Community (EC, now EU), the French and Belgian authorities decided to make a study of coastal protection in this trans- border area. Several methods for coastal protection were envisaged. The solution proposed to prevent further erosion of the subtidal zone in the Belgian territory consists of a perched beach. 2. Westhoek (Nature Reserve) After the extremely severe 1953 storm, seawalls were built at several places along the Belgian coast. During the 1976 storm, the sea breached the first dune ridge West of De Panne in four places and entered the nature reserve called Westhoek. Shortly after this breach, a dune toe-protection was built running over 1,300 m all the way to the French-Belgian border (Fig. 2). NORTH SEA ~km : 0111'1/(<,.t The Flemi sh Banks ~ ~Q(jF:'v. ------ ---(~;~R CONSTRUCTlO:;::-"""'",,,,, FIGURE 2 Location Map Westhoek and border area DunkerqueDe Panne (Haecon). TO FEED 5 At present, dismantling the currently severely damaged dune toe- protection is envisaged in order to allow salt/fresh water exchange and promote the development of particular ecosystems. A detailed study was performed about morphological stability of the intertidal zone and of the dune profiles in order to establish the feasibility of the project and assess the safety against risk of flooding (Figs. 3-5). The North Sea had, in bygone times, free access to some inland areas. Indeed, Het Zwin was an embayment which allowed ships to reach Bruges-the one-time "Venice of the North" and the richest harbor and city of Western Europe-. Silting led to the occlusion of the opening and the demise of Bruges' portuary commerce. Today, the remnants of the Zwin are a protected nature reserve. Similarly, the sea had access to areas of the dunes of De (La) Panne. Allowing again an opening in the coastal dunes string is an option considered by the Coastal Waterways Division for areas such as the West hoek's Nature Reserve. It would thus entail removal of a concrete protection struc- ture at the foot of the dunes. The height of the dunes is sufficient and so is their width to allow the abandon of a small part of them to the sea, and thus re-establish the once prevailing interaction between land and sea. The approach has been tried in France and has not resulted FIGURE 3 De (La) Panne. Belgium; Coastal dunes where an "inlet" for tidal waters is under consideration in lieu of repair to the toe (Photo. Het Volk. Ghent. Belgium). 6 R. H. CHARLIER et (/1. FIGURE 4 Coxyde. Belgium. Beach and seawall prior to rehabilitation works (Char- lien. in floods; to the contrary the alternance of dry and wet conditions has favored the development of unique flora and fauna. Not only beach protection but also defense against inland floods are of concern. It has been estimated witness the 1953 storm when even the Zwin, on the Belgian/Dutch border, fillednthat were the dikes to give way, the sea would invade the land up to twenty kilo- meters inland.