ABSTRACT• The paucity of information about stepwise regression has led the authors to compile this account because of its potential value in addressing synergistically complex environmental issues. Useful sources are identified for researchers who may wish to compile their own stepwise regression (all possible regressions) application. Results from one such application are documented herein. The example used to document stepwise regression is concerned with determining the best numerical method to predict where nearshore waves shore‐break. The original definition posited by McCowan in 1894 suggested that nearshore waves are water depth limited (i.e., related to water depth only). Subsequent investigators, feeling the answer must be more complicated, have included bed slope, wave steepness considerations, the surf similarity parameter, and other parameters in endeavors to “refine” predictive power. However, this study confirms to a highly significant level that nearshore waves are depth limited. Statistical results indicate that db = 1.277 Hb, where db is the water depth at the shore‐breaking position and Hb is the average shore‐breaking wave height. The result is so close to the McCowan original result of db = 1.28 Hb that McCowan's relationship prevails as the standard instrument for prediction.
The wave energy loss as waves break on nearshore bars is an important geomorphological process as it controls the stability of the adjacent beaches and dunes. The effect is particularly important during storms as it serves to guard against severe shoreline erosion.Field measurements from Florida and Ireland of waves crossing both single and multiple bar bedforms, indicate that where bar-breaking occurs, between 78 and 99 per cent of wave energy may be dissipated from individual waves. However, a further 20 per cent energy may reach the shore if wave frequencies increase during the reformation process. This latter effect was not noted at the multiple bar site where spilling mode breakers dominate. The level of energy dissipation is related to the time taken to cross that section of the submerged bar below the critical depth, d < 1.28H. In the field this may be approximated by the ratio of wave speed to the width of the bar breaker zone.
The Ryan/Harley site (Florida Master Site File Number: 8Je-1004) is a Middle Paleoindian habitation site containing Suwannee points. Based on stratigraphic correlation and diagnostic artifact seriation, Suwannee-age sites have been relatively dated from ~10,900 14 C yr B.P. to ~10,500 14 C yr B.P. Clovis-like traits on the Suwannee points and other stone tools from the Ryan/Harley site suggest it dates to the earlier end of the Suwannee timeframe. The currently inundated site is partially buried beneath a sediment column located in a swamp forest and partially exposed in a side channel section of the Wacissa River, Jefferson County, Florida. Research done prior to this analysis determined that the artifact assemblage appeared to be unsorted and was contained in a midden-like unit. Our purpose here is to assess the issue of site integrity further. Unconsolidated sediment samples collected from the artifact-bearing horizon and from horizons immediately above and below the artifact horizon were analyzed using granulometric techniques. Arithmetic probability plots of the grain-size distributions show that the sediments were transported and deposited by fluvial processes. Thus, the Suwannee points and associated artifacts, and faunal remains appear to have accumulated during a time of subaerial exposure perhaps after a regional water-table decline, and have remained largely or essentially intact, with little or no postdepositional reworking. The artifacts and faunal remains recovered from the artifact-bearing horizon at Ryan/Harley are distributed randomly, showing no sign of sorting. In the fossil suite, two articulated white-tailed deer (Odocoileus virginianus) vertebra were recovered in situ. The unsorted nature of artifacts and articulated faunal remains that are contained within the fluvially deposited sediments suggests the Suwannee point level of the Ryan/Harley site has remained undisturbed since original deposition.
An annotated bibliography on groins, compiled by Balsillie and Bruno (1972J, has provided the background for this paper. A review of functional design criteria is presented including groin length, height, spacing, permeability-adjustability, and orientation. A discussion of coastal processes and their relationship to groin design and effectiveness is" also given.
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