Simulating nearshore processes

Computer procedures are presented that simulate sediment transport in coastal environments. More specifically, these procedures simulate erosion, transport, and deposition by waves. A principal objective is to show how nearshore processes can be described mathematically and translated into computer procedures for simulating the formation of sedimentary deposits. The computer procedures, incorporated into a FORTRAN 77 program called "WAVE", are in many ways unique because they provide a three-dimensional simulation model that involves multiple grain types, records ages and compositions of sediments, operates at a variety of scales, and simulates the passing of a few seconds or a few thousand years. WAVE simulates wave refraction, oscillatory wave motion, longshore currents, rip currents, and nearshore sediment transport, and is dynamic in that the effects of wave energy on an evolving coastline are simulated through time. WAVE employs equations based on the principles of fluid dynamics to describe hydrodynamic characteristics of shoaling wave and to calculate wave-induced currents within a grid network. The equations assume that mass and momentum are conserved as waves shoal towards shore. A finite-difference scheme provides solutions for wave equations at each cell in the grid. Once characteristics of shoaling waves are represented, sediment transport is initiated using empirical relationships that are effective in predicting rates of littoral transport. WAVE is tested with data from modern beaches, where experiments span hundreds or thousands of meters, and involve days, weeks, or a few years. WAVE is also used to simulate larger areas where experiments span tens or hundreds of kilometers and involve hundreds to thousands of years. Results of experiments are displayed with contour maps and three-dimensional color displays that can be compared with actual nearshore environments. Experiments document WAVE's application at a variety of scales, but also show how assumptions incorporated into WAVE may limit its application. WAVE's computer procedures may be useful for engineers who require quantitative estimates involving coastal or beach systems or geologists who study ancient sedimentary deposits influenced by nearshore sediment transport.