Journal ofCoastal Research 1132-1144 Royal Palm Beach. Florida Fall 1999 The Evolution of the Island of Neuwerk, Elbe Estuary, North Sea Alex Chepstow-Lustyt, J iirgen Ehlers[, and Gerhard Linke] t University of Cambridge :j:Geologisches Landesamt Botany School. Downing Billstr. 84 Street D-20539 Hamburg, Germany Cambridge CB2 3EA, England ABSTRACT _ CHEPSTOW-LUSTY, A., EHLERS, J., and LINKE, G., 1999. The Evolution of the Island of Neuwerk,Elbe Estuary. .tllllllll:. North Sea. Journal of Coastal Research, 15(4), 1132-1144. Royal Palm Beach (Florida). ISSN 0749-0208. ~ On samples recovered from trench profiles on Neuwerk, a little island on the German North Sea coast. palynology. euus~_~ 1f heavy metal and cesium analyses were carried out in order to reveal the historical development of the island. All three analytical approaches yielded good results with regard to the relatively recent developments. The cesium de­ --+ &-- terminations suggest that sedimentation during most of the last fifty years has been in the order of 2.1 rn rn/yr , but under the influence of increased storm surge heights and frequencies has recently accelerated to about 6.0-7.5 mm/yr. The earlier history of the island is revealed by stratigraphical investigations. Aclear sequence ofvegetationsuccession is recorded, which is followed by a series of plant communities maintai ned by animal grazing. ADDITIONAL INDEX WORDS: Pollen analysis. heavy metals. cesium . Waddell Sea. INTRO DUCTION tury, which were destroyed again before 1914. In 1927 sa nd fencing and planting of Ammophila arenaria resulted in dune Neuwerk (Figures 1 and 2) is situated in the inner part of and salt marsh form ation. The island has been eroding on the German Bight, adj acent to th e Elb e Estuary. It lies half th e NW side and growing on th e SE side ever since, resulting way betw een the outer margin of the intertidal zone and th e in a shift of well over 1 km since 19:30, i.e. about 16 m/yr ma inland coast. Tid al range in this area is slightly above 3 (LANG , 1970 ; EHLERS, 1988 ), m. According to the classification of HAYES (l975) this would suggest a mesotidal environme nt. EHLERS (l988) has intro­ Tri sch en (north of th e Elbe estua ry ) was first mentioned in a legal document in 1610. It developed from a 'very low sand' du ced a different classification ada pted to North Sea condi­ tions. According to this scheme th e area is located in the 'ma­ (l689) to a little island with patches of salt marsh (since crotida l' zone. No permanent barrier islands are found be­ 1854) and dunes (since 1885). In 1907, aft er a sequence of tween th e easternmost East Frisian Island ofWangerooge in setbacks and recoveri es, a vegetate d area of 80 ha had de­ Niedersachs en (Lower Saxony) and the Eiderstedt Peninsula veloped . The island was dik ed in 1925 by a farm er, but ero­ in Schleswig-Holste in, i.e. in a n area where tidal range ex­ sion in th e west outpaced accretion in th e eas t. The dik e was ceeds 2.90 m. Instead, th e are a is occupied by wide, open tid al breach ed in 1942 a nd th e polder was lost. Tri schen has shift­ flat s with highly mobile sand banks, a few of which have ed eastward about 1 km sinc e 1930 (LAN G, 1975;EHLERS, developed into fragil e islands in the course of th e last cen­ 1988). tury: Neuw erk differs from those islands in th at it consists en­ Mellum (betw een the Jade and Weser estuaries) was tirely of sa lt marsh . It neither developed from a sa nd bank known to be a n elevate d sand bank since the Middl e Ages; in relatively recent times, nor was it carved out of coas ta l however, salt marsh es pr otected by low dunes only starte d to wetlands in historical times like th e Hall igen in Schleswig­ develop shortly before 1879 (REINECK, 1987 ). The island is Holstein , but it has been kn own as a marsh island since th e highly mobil e; between 1962 and 1978 it migrated 250 m to­ Middle Ages, being first men tion ed in 1286. Its origina l nam e wards th e SE , i.e. approximately 15.6 m/yr. 'Nova 0 ' (Ne w Island) does not neccessarily suggest that it Scharhorn (between th e Weser and Elb e es tuaries, seeward had recently formed, since place nam es have a tradition of of Neuw erk) was kn own to be a high sand bank since th e not bein g cha nged (LANG, 1970 l. Th e island has und ergone 13th century. Geological investigations suggest that it formed some land losses, but it ha s not shifted like its three younger mu ch earlier, when th e sea-level rise reach ed th e north Ger­ neighbours mentioned above. However , its origin and its re­ man coas t, some 3,500 years BP (LINKE, 1969 ). Th e nam e lation to th e sa lt marsh development on th e mainl and coast, Scha rhorn first a ppea red in docum ents dating from 1466. It south of Cuxhaven , is not clea r (LINKE, 1979,1 982). developed dunes more th an 5 m high in th e late 19th Cen- A number of boreholes in and a round Neuwerk have re­ vealed th at th e island is not sit ua ted on top of a silted-over 9704 8 received 28 May 1997; accepted ill revision 28 October 1997 Pleistoc ene core (Figures :3a and h). Th ere is only a thi n cover The Evolution of the Island of Neuw erk 1133 4 0 I-: 7 0 Bllnndshuk .,. " ~~o N IJ---+---+---+---':f---F--4"' . NORTH SEA Helgoland ~ 5 0 ~JO Bremen II ~ll km E3 E3 E3 Figure 1. Locat ion map of Neuwerk a nd th e north German coas t. of salt marsh sediments overlying Holocene marine sands island was much larger (LANG, 1970). Th e salt marshes were which reach down to a depth of approximately 15-20 m (LINKE , used for cattle and sh eep grazing, and agri culture started on 1970). the polder in 1564 . The relatively sandy soil of the polder allows the production of rye, wheat, oats and beans (VON Historical Evidence LEHE, 1952). Though the Isle of Neuw erk was first mentioned in a doc­ Neuwerk is a marsh island, surrounded by very sa ndy tid al ument of 1286, it probably form ed mu ch earlier. Th e impres­ fiats. Old reports mention sanding-up of th e island on a num­ sive stone tower on th e island (Figure 4), erecte d by th e City ber of occasion s. A docum ent dealing with the storm surge of of Hamburg 1300-1310 as a protective measure against 1717 reports that the sa lt marshes in th e west were largely beach robbery , gave rise to its present name (Neuwerk = covered by sa nd, and that the polder field s were spoiled by New Work s) (DANNMEYER et al., 1952 ; VON L EHE, 1952, sand wash ed in through the breached dike. Heavy dam age 1973). The island was diked betw een 1556 and 1559 , and was also caused by another storm surge in 1825. A map of since th e polder area measured during the first primitive sur­ 1787 shows a broad belt of sand dunes at th e northern edge vey of Neuw erk in 1574 is almost identical with its present of Neuw erk. The dunes also a ppear on a map of 1854. They size, it can be assumed tha t no major changes have occurred are still featured on the first edition of th e 1:25,000 map of since. Nothing is known, however, about the exte nt of the 1878, extending to a height of 2.8-3.3 m above NN (German und iked sa lt marsh es at th at time, although allegedly the Ordnance Datum). Th ey could still be t ra ced until 1904 , when Journal of Coasta l Research, Vol. 15, No. 4, 1999 1134 Che psto w-Lusty, Ehlers and Link e Figure 2. Aerial photograph of Neuwerk (1989 ). th eir remnants disappeared under coastal protection struc­ been completely halted by th e constru ction of th e revetments, tures (LANG, 1970). Neuw erk is now protected by a re vet­ and there are even signs of minor accretion in th e east. ment, completed in 1931 (UHL, 1952 ). The salt marsh es are additiona lly protected by a low summer dike of about th e Vegetation sa me age . The exis te nce of the island is not threatened as it is situated on high tidal flats a cons iderable distance from The veget ation of the undiked sa lt marsh es ofNeuwerk has th e Elbe river and othe r major channels. Coas tal erosion has been studied by TOX EN et at. (1957), MANG (1982) and R UD - Journal of Coasta l Research, Vol. 15, No.4, 1999 The Evolution of the Island of Neuw erk 1135 s N Neuwerk storm su rge depo sits dike tidal flats intercalated with (not to scale) salt marshes aeo lian sa nd tidal flats MTHw .!1.-- NN clay:wilh Scrn~ (a ria MTt w . she H S bl 1 ife po s t1 1Q n .