SIMULATION OF REGIONAL LONGSHORE SEDIMENT TRANSPORT AND COASTAL EVOLUTION

ICCE02_Cascade
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Magnus Larson 1, Nicholas C. Kraus2, and Hans Hanson1

Abstract: A numerical model called Cascade is introduced for simulating

regional sediment transport and coastal evolution. Cascade can be applied to

stretches of coastline covering hundreds of kilometers where evolution

extending to centuries may be of interest. A typical setting encompasses several

barrier islands separated by inlets at which sediment is transferred through tidal-

shoal complexes. Complex regional trends in shoreline orientation can be

represented, as well as sediment sources and sinks, such as beach nourishment,

cliff erosion, wind-blown sand, and dredging. Processes are modeled at the

local and regional scale, and the interaction between the scales is described in a

cascading manner from regional to local. Main components of the model are

described, followed by an application to the south shore of Long Island, New

York, where the regional sediment transport pattern was simulated, including

opening of two inlets and the response of the adjacent shore.

INTRODUCTION

Many coastal projects have been in place for more than a century, and their ranges of

influence far exceed local project dimensions. For example, both stabilized inlets and

natural inlets can alter longshore sediment-transport pathways for tens of kilometers. Sand

placed on beaches likewise will travel far beyond project limits. The time and space scales

of major coastal projects therefore call for regional modeling to address the full

consequences and interactions of engineering activities, as well as the wide-scale of

influence of natural processes and features (Larson , Rosati, and Kraus 2002). Quantitative

descriptions of regional coastal-sediment processes are lacking, and their consideration

raises new and interesting questions, together with many challenges.

1. Professor, Water Resources Engineering, Lund University, Box 118, S-221 00 Lund, Sweden.

Magnus.Larson@tvrl.lth.se,

2. Senior Scientist, US Army Engineer Research and Development Center, Coastal and

Hydraulics Laboratory, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199 USA.

Larson, Kraus, and Hanson