Beach face dynamics as affected by ground water table elevations

This report presents the results of laboratory studies which were carried out in the Coastal and Oceanographical Engineering Laboratory to investigate the effects of ground water table elevations on the beach profile changes over the swash zone. The experiment was conducted at three different water table levels while the other experimental conditions were fixed to constant values with regular waves. The water table levels included (1) normal water table level which is the same as mean sea level, (2) a higher level and (3) a lower level than the mean sea level. Special attention was given to the higher water level to investigate whether this level enhances erosion of the beach face and also to methods of interpreting the experimental data. The experiment described herein was carried out with a fairly fine sand and has demonstrated the significance of beach water table on profile dynamics. The increased water table level caused distinct effects in three definite zones. First, erosion occurred at the base of the beach face and the sand eroded was carried up and deposited on the upper portion of the beach face. Secondly, the bar trough deepened considerably and rapidly and the eroded sand was deposited immediately landward. This depositional area changed from mildly erosional to strongly depositional. Third, the area seaward of the bar eroded with a substantial deepening. The lowered water table appeared to result in a much more stable beach and the resulting effects were much less. The only noticeable trend was a limited deposition in the scour area at the base of the beach face. (Document has 37 pages.

Florida's West Coast inlets: shoreline effects and recommended action

This report responds to the 1986 Beaches Bill which, in recognition of the potential deleterious impact on Florida's beaches of inlets modified for navigation, mandated a study of those inlets with identification of recommended action to reduce the impacts. This report addresses west Coast inlets; East Coast inlets are the subject of a companion report. There are 37 inlets along that portion of Florida's West Coast commencing from Pensacola Bay Entrance to Caxambas Pass at the south end of Marco Island. Compared to those on the East Coast, most West Coast inlets have not had the deleterious effects on the adjacent beaches, yet all modified inlets without proper management have the potential of impacting unfavorably on the adjacent shorelines. Moreover, at present there is interest in opening three West Coast entrances which either have been open in the past (Midnight Pass) or which have opened occasionally (Navarre Pass and Entrance to Phillips Lake). A review of inlets in their natural condition demonstrates the presence of a shallow broad outer bar across which the longshore transport Occurs. These shallow and shifting bar features were unsuitable for navigation which in many cases has led to the deepening of the channels and fixing with one or two jetty structures. Inlets in this modified state along with inappropriate maintenance practices have the potential of placing great ero$ional stress along the adjacent beaches. Moreover. channel dredging can reduce wave sheltering of the shoreline by ebb tidal shoals and alter the equilibrium of the affected shoreline segments. The ultimate in poor sand management practice is the placement of good quality beach sand in water depths too great for the sand to reenter the longshore system under natural forces; depths of 12 ft. or less are considered appropriate for Florida in order to maintain the sand in the system. With the interference of the nearshore sediment transport processes by inlets modified for navigation, if the adjacent beaches are to be stabilized there must be an active monitoring program with commitment to placement of dredged material of beach quality on shoreline segments of documented need. Several East Coast inlets have such transfer facilities; however. the quantities of sand transferred should be increased. Although an evolution and improvement in the technical capability to manage sand resources in the vicinity of inlets is expected, an adequate capability exists today and a concerted program should be made to commence a scheduled implementation of this capability at those entrances causing greatest erosional stress on the adjacent shorelines. A brief summary review for each of the 37 West Coast inlets is presented including: a scaled aerial photograph, brief historical information, several items related to sediment losses at each inlet and special characteristics relevant to State responsibilities. For each inlet, where appropriate, the above infor~tion is utilized to develop a recommenced action. (PDF has 101 pages.

Short course on principles and applications of beach nourishment

Covers the engineering aspects of beach nourishment. (Document is 192 pages

Barrier island erosion and overwash study -- effect of seawalls. Volume 2

This is the second of a pair of reports documenting the effects of storms on beach systems including the presence of seawalls. With the aim of simulating the effects of overwash on barrier islands with seawalls and characterizing their response, a series of eight experiments was conducted at the Coastal Engineering Laboratory of the University of Florida. The barrier island was simulated by a 400 feet wide horizontal crest and an initially uniform mildly-sloped (1:19) beach. The effects of positioning the seawall at two different locations as well as the effects of various storm surge levels and accompanying overtopping were investigated. Experiments were conducted with both regular and irregular storm waves. With the seawall located at the slope break between the crest and the sloping beach of the barrier island, and the crest of the seawall just submerged in sand, the effects on the sediment transport process were found to be minimal. For the same position of the seawall but with the crest of the seawall raised above the surrounding ground level, overtopping caused washover of sand indicating substantial transport in suspension. Increased levels of overtopping tended to accentuate bed profile changes but supress bar formation (as did irregular waves). Positioning the seawall at the Mean Sea Level shoreline caused significant scour both immediately landward as well as immediately seaward of the seawall. A prominent scour trough developed further seaward. The longshore bar was highly three-dimensional. It appears that seawalls need to be located adequately landward of the shoreline to discharge their function effectively without adverse effect to the beach. In addition, concerns for safety warrant the presence of an adequate buffer-zone between the seawall and the upland property. (61 pp.

Shoreline erosion due to extreme storms and sea level rise

A summary is presented of research conducted on beach erosion associated with extreme storms and sea level rise. These results were developed by the author and graduate students under sponsorship of the University of Delaware Sea Grant Program. Various shoreline response problems of engineering interest are examined. The basis for the approach is a monotonic equilibrium profile of the form h = Ax2 /3 in which h is water depth at a distance x from the shoreline and A is a scale parameter depending primarily on sediment characteristics and secondarily on wave characteristics. This form is shown to be consistent with uniform wave energy dissipation per unit volume. The dependency of A on sediment size is quantified through laboratory and field data. Quasi-static beach response is examined to represent the effect of sea level rise. Cases considered include natural and seawalled profiles. To represent response to storms of realistic durations, a model is proposed in which the offshore transport is proportional to the "excess" energy dissipation per unit volume. The single rate constant in this model was evaluated based on large scale wave tank tests and confirmed with Hurricane Eloise pre- and post-storm surveys. It is shown that most hurricanes only cause 10% to 25% of the erosion potential associated with the peak storm tide and wave conditions. Additional applications include profile response employing a fairly realistic breaking model in which longshore bars are formed and long-term (500 years) Monte Carlo simulation including the contributions due to sea level rise and random storm occurrences. (PDF has 67 pages.

Development of methodology for thirty-year shoreline projections in the vicinity of beach nourishment projects

The purpose of this report is to develop and illustrate with examples readily applied methodologies for calculating the response of shorelines in the vicinity of beach nourishment projects. The need for such methodology is a result of Florida Statutes 161.053(G) and Rule 16B-33.024(3)(e) which require, with minor exceptions, coastal structures to be located landward of a thirty- year projection of the Seasonal High Water Shoreline (SHWL). (163pp.

Some considerations on coastal processes relevant to sea level rise

The effects of potential sea level rise on the shoreline and shore environment have been briefly examined by considering the interactions between sea level rise and relevant coastal processes. These interactions have been reviewed beginning with a discussion of the need to reanalyze previous estimates of eustatic sea level rise and compaction effects in water level measurement. This is followed by considerations on sea level effects on coastal and estuarine tidal ranges, storm surge and water level response, and interaction with natural and constructed shoreline features. The desirability to reevaluate the well known Bruun Rule for estimating shoreline recession has been noted. The mechanics of ground and surface water intrusion with reference to sea level rise are then reviewed. This is followed by sedimentary processes in the estuaries including wetland response. Finally comments are included on some probable effects of sea level rise on coastal ecosystems. These interactions are complex and lead to shoreline evolution (under a sea level rise) which is highly site-specific. Models which determine shoreline change on the basis of inundation of terrestrial topography without considering relevant coastal processes are likely to lead to erroneous shoreline scenarios, particularly where the shoreline is composed of erodible sedimentary material. With some exceptions, present day knowledge of shoreline response to hydrodynamic forcing is inadequate for long-term quantitative predictions. A series of interrelated basic and applied research issues must be addressed in the coming decades to determine shoreline response to sea level change with an acceptable degree of confidence. (PDF contains 189 pages.

Florida's East Coast Inlets: shoreline effects and recommended action

A brief summary review for each of the 19 inlets on Florida's East Coast is presented including: a scaled aerial photograph, brief historical information, several items related to sediment losses at each inlet and special characteristics relevant to State responsibilities. For each inlet the above information is utilized to develop a recommended action, usually in the form of periodic sand transfer quantities. (PDF contains 67 pages

Perdido Key Beach nourishment project: Gulf Islands National Seashore 1992 annual report

This report is the third annual report in a continuing series documenting a field project within the Gulf Islands National Seashore at Perdido Key, Florida. The field project includes the monitoring of a number of physical parameters related to the evolution of the Perdido Key beach nourishment project. Approximately 4.1 million m3 of dredge spoil from Pensacola Pass were placed upon approximately 7 km of the Gulf of Mexico beaches and 3 million m3 offshore of Perdido Key between November, 1989, and October, 1991. Beach profile data describing the evolution of the nourished beach are included, as well as wave, current, tide, wind, temperature, and rainfall data to describe the forces influencing the evolution. Data describing the sediment sizes throughout the project area are also included. A brief discussion of the data is included with an emphasis on evolution of the beach and offshore nourishment. (Document contains 249 pages.

Perdido Key Beach nourishment project: Gulf Islands National Seashore 1991 annual report

This report is the second annual report in a continuing series documenting a field project within the Gulf Islands National Seashore at Perdido Key, Florida. The field project includes the monitoring of a number of physical parameters related to the evolution of the Perdido Key beach nourishment project. Approximately 4.1 million m3 of dredge spoil from Pensacola Pass were placed upon approximately 7 km of the Gulf of Mexico beaches of Perdido Key between November, 1989, and September, 1990. Beach profile data describing the evolution of the nourished beach are included, as well as wave, current, tide, wind, temperature, and rainfall data to describe the forces influencing the evolution. Data describing the sediment sizes throughout the project area are also included. A brief discussion of the data is included; a more detailed analysis and interpretation will be presented in the lead author's Ph.D. dissertation. (313 pp.