To Appear: Proceedings 28th Coastal Engineering Conference, World Scientific Press, 2002.
SIMULATION OF REGIONAL LONGSHORE SEDIMENT TRANSPORT AND
COASTAL EVOLUTION THE "CASCADE" MODEL
Magnus Larson1, 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.
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.
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