ELsEVIER MARINE GEOLOGY -- _1fNAI. 01' MARlNIl -~r.~AND_' Marine Geology 189 (2002) 227-247 www.e1sevier.com/1ocate/margeo , r I ./ Environmental controls on decadalmorphologic behaviour of , "I . , the Holland coast Kathelijne M. Wijnberg' t \ , Department of Physical Geography, Institute for Marine and Atmospheric Research Utrecht, Utrecht University, . P.O. Box 80115,3508 TCUtrecht, .The Netherltmds R(:ceived27 July 2001 ; received in, revised form 22 May 2002; aCCepted '19 July 2002 Abstract A detailed comparison of alongshore variation in environmental variables along the Hollandcoa~t with the observed marked regional differences in decadal. nearshore ~orphologic behaviour reveals that neither offshore hydrodynamic parameters nor gr~n size are discrffi'\inating factors, 'Rather; the abrupt alongshore changes in'decadal behaviour coincide with sharp changes ip shoreface rp.orphologyand the. location of large man~made structures.. These structures, such as jetties and a protruding seawall, appear to act as artificial headlands. Once they are bUilt, the coastal stretches opeither side of the structure can develop independently of each other; initially smalL differences in the development of the regions potentially may evolve into larger differences with time. Consequently, On the long' term, large man-made structures may affect the ,behaviour of coastal stretches over far larger distanCes than was previously known. @ 2002 Elsevier Science B.V. All rights reserved. Keywords: nearshore rnorphpdynami'1s; alongshore variability; coasta1'engineering; coastal evolution; large-scale coasta1.pehaviour ; '! 1. Introduction , , In low-lying and densely populated countries like the Netherlands, the understanding and pre- diction of large-scale and long-term changes of 'the coast are. of vital importance. Decades are a typical time scale of interest for long-term coastal management, while spatial scales of interest range from kilometres to tens of kilometres. Surpris~ ingly, little, is known about the, contrplling mech- anisms for the behaviour of large coastal. stretches over'decadal time spans (e.g. De Vriend, 1998).In E-mail address:k.wijnberg@geog.uu.n1(K.M..Wijnberg). IB,rgegeomorphic systems such as these the con- struction of'successful.niodels is likely to be based upon discovery, of emergent variables and corre- sponding dynamics at the given scale, rather than upon scaling up the results of well-controlled small-scale, sediment transport studies (Haff, 1996). ' Long-term ,coastal data sets covering large stretches of coast can be used to reveal the nature of the vari,ability in coa~tal morphology. occurring over aJew decades. For instance, the analysis of three decades, of annual bathymetric surveys' along the Holland coast revealed marked patterns in nearshore morphologic behaviour (WGnberg and Terwindt, 1995); It appeared that alongshore changes in decadal morphologic behaviour were 0025-3227/02/$- see front matter@ 2002 Elsevier Science B.V. All rights reserved. PIl:S 00 2 5.32 27 (02) 0 04 8 0-2