The effect of structures and lake level on bluff and shore erosion in Berrien County, Michigan, 1970-74

Source: https://erdc-library.erdc.dren.mil/jspui/Rates of bluff recession and shoreline change along five 1. 6-kilometer reaches located within Berrien County, Michigan, between 1970 and 1974 were measured by use of aerial photos. Annual measurements were made at 30.5-meter intervals, except for two adjacent reaches where biannual measurements were made. The overall average rate of recession for the five reaches was 3.8 meters per year. Average recession rate varied from 2.4 meters per year for a reach with low foredunes to 4.5 meters per year along a reach with a high sandy bluff. The greatest amount of recession resulted from a significant storm occurring 16 to 18 March 1973. Simple regression analysis of the data from both lake level and storm parameters ldentified storms as the primary cause of recession. However, the data set was too small and at such a unique point in the long-term lake level cycle (the crest of a rising peak) to quantify the effect of lake level. The effect of a 579-meter-long seawall constructed during the study is discussed; the volume of material eroded downdrift of the wall nearly equaled the amount of material removed from the sediment supply by the seawall. The procedures used in analyzing the air photos and their accuracy are described in an Appendix. Guidance is also given for determining the number of measurement points needed per distance along the shore depending on the desired accuracy of the bluff recession rates

Coastal Changes, Eastern Lake Michigan, 1970-74

Source: https://erdc-library.erdc.dren.mil/jspui/Bluff recession and volumetric losses at 17 profile lines along the eastern shore of Lake Michigan were measured monthly from August 1970 to December 1974. Average rate of bluff recession for the period equaled 2.5 meters per year per profile line with an average loss of 4.2 meters per year on the most severely eroded line. Bluff recession tended to increase with lake level but the seasonal peak in recession coincided with the storm period (September to April). Peak recession occurred before ice buildup (between November and December) and just after ice breakup (in the spring, March to April). Lake ice was found to be an effective shore protection agent during the stormiest months of January, February. and March. Till and mixed till bluffs tended to erode less than bluffs composed of sand , but no clear dependence on bluff composition was found. An analysis of the content and median sand size of 519 sediment samples collected from both the foreshore and the backshore during the final 15 months of surveying shows that backshore sediments are generally finer and more uniform than foreshore sediments. High and low concentrations of gravel, usually found on the foreshore, were characteristic of specific profile lines. Deposits of heavy minerals, predominantly magnetite, were usually found on the backshore

Fast, Accurate Two-Person Beach Surveys

Source: https://erdc-library.erdc.dren.mil/jspui/Generally, the most accurate beach survey data are obtained using a surveying level to determine elevation and a tape to measure distance; however, this procedure requires a minimum of three people. Commonly used two-person surveying procedures are stadia surveying and the Emery method. In stadia surveying, a level is used to determine elevation; distance is indirectly determined by two additional readings of the level rod. This method gives the same elevation accuracy of level and tape surveying, but requires careful readings of the level rod to obtain accurate distances. The Emery method uses two 5-foot calibrated rods and the horizon to measure distances to, and changes in elevation between, two survey points. Errors are additive and large elevation errors are possible, particularly on wide beaches. This report discusses a modified stadia surveying procedure which, when used properly, is fast and produces data of comparable accuracy to level and tape surveying. Because more readings are taken (three per survey point), the data provide a higher degree of confidence than is available with the other methods. The modifications include the addition of two stakes to the profile line monumentation, pacing the distance between each point, and performing a simple mental field check of data quality. Using the stadia method, a typical profile of 10 to 15 survey points can be surveyed in 15 to 20 minutes including instrument setup time

Field comparison of four nearshore survey systems

Source: https://erdc-library.erdc.dren.mil/jspui/Four types of nearshore survey systems used by the US Army Corps of Engineers were evaluated at the Coastal Engineering Research Center's (CERC's) Field Research Facility in Duck, N. C., during 1984 under ideal conditions. The systems include a survey boat with fathometer and microwave positioning, CERC's Coastal Research Amphibious Buggy (CRAB) and a boat-towed sea sled used with an electronic total station, and a hydrostatic profiler developed by the Scripps Institution of Oceanography. The systems were evaluated on the basis of accuracy, repeatability, cost, speed, and manpower

Hand-Held Calculator Algorithms for Coastal Engineering

Source: https://erdc-library.erdc.dren.mil/jspui/This report provides algorithms for a number of calculator programs useful in performing coastal engineering calculations, primarily in the area of wave transformations and wave generation. Six programs are included with different versions for use with hand-held calculators which employ either the Reverse Polish Notation (RPN) or the Algebraic Operating System (AOS). These programs can be used to compute linear wave parameters, orbital velocities, breaking wave height and direction, shallow-water wave forecasts, depth-limited breaking wave height, and wave transmission past a vertical barrier

Cooperative Laboratory and Field Study to Investigate Effects of Wave and Current Action on Dual-Rocket Distributed Explosive Array Deployment

Source: https://erdc-library.erdc.dren.mil/jspui/A series of 2-D (flume) laboratory and field tests were conducted to examine effects of waves and currents on a simulated dual-rocket distribution explosive array deployment (DRDEAD) system. The DRDEAD system consists of a large array of explosive material which can be deployed by rockets launched from Navy vessels across the surf zone in a mine-clearing operation. The U.S. Anny Engineer Waterways Experiment Station (WES) Coastal Engineering Research Center's mid-scale 2-D facility was used to examine various wave conditions, methods of deployment, and anchoring systems for a simulated (inert) DRDEAD. Waves simulating sea state 3 conditions and lower (i.e., calm seas to 5-ft prototype waves) were used in the laboratory study. Laboratory tests indicated that sea state 3 will be a limiting condition for deployment of the array without additional weights or anchors. Field tests to assess effects of wave and current were conducted during the summer of 1992 at CERC's Field Research Facility (FRF) in Duck, North Carolina. Results of the field tests supported laboratory findings, but also indicated that longshore currents are likely to have equal or greater effects on the DRDEAD system and must be considered in the final design