Lorelle A. Meadows

The Relationship between Great Lakes Water Levels, Wave Energies, and Shoreline Damage

The latter half of the twentieth century can be characterized as a period of rising water levels on the Great Lakes, with record high levels in 1974 and 1986. Concurrent with these periods of high water level are reported periods of high shoreline damage and property loss. Water levels of the Great Lakes are determined by precipitation, evaporation, river outflow, and groundwater inflow, while wave energy is primarily a function of wind speed, duration, and fetch. A comparison between a recently completed long-term (1956–87) wave climate hindcast and historical lake levels for the Great Lakes shows a strong correlation between periods of high wave energy and high lake levels. Statistical comparison of these two time series indicates an approximately constant correlation from +24 months to −6 months, around a zero lag/lead. The causational link between increasing lake levels and more intense wind-generated waves appears to be related to significant changes in the climatology of Great Lakes basin cyclones....

Cumulative Habitat Impacts of Nearshore Engineering

Abstract A multi-disciplinary, multi-institutional research team evaluated a broad range of physical and biological characteristics at six Great Lakes nearshore sites in order to develop and test a conceptual modeling framework to assess linkages between bluff erosion, sediment supply, coastal processes, and biological utilization of nearshore and coastal habitats. The sites were chosen to represent a broad range of hydrogeomorphic conditions, with the objective of assessing the response of these nearshore systems to anthropogenic modifications and coastal change. As a result of this 2-year field effort, new methods and integrated approaches were developed to characterize, map, and assess the dynamic nature of the nearshore zone (area generally less than 10 m water depth). Thus, these data provide an initial quantitative assessment of nearshore change. In addition, our data indicate that shoreline modifications have led to cumulative impacts that have irreversibly modified Great Lakes nearshore coastal habitats and the processes that create and maintain them. Of special note is our observation that altered nearshore substrate dynamics resulting from shoreline modifications may enhance the colonization success of lithophilic aquatic invasive species in nearshore areas of the Great Lakes. Continued development of the shoreline may exacerbate changes in Great Lakes nearshore food-web structures and ecosystem services. Further study and monitoring of these phenomena are needed, and our work suggests that a holistic, multidisciplinary approach is necessary to develop effective management strategies to address these and other issues affecting nearshore areas of the Great Lakes.

Surface current measurements by HF radar in freshwater lakes

HF radar has become an increasingly important tool for mapping surface currents in the coastal ocean. However, the limited range, due to much higher propagation loss and smaller wave heights (relative to the saltwater ocean), has discouraged HF radar use over fresh water, Nevertheless, the potential usefulness of HF radar in measuring circulation patterns in freshwater lakes has stimulated pilot experiments to explore HF radar capabilities over fresh water. The Episodic Events Great Lakes Experiment (EEGLE), which studied the impact of intermittent strong wind events on the resuspension of pollutants from lake-bottom sediments, provided an excellent venue for a pilot experiment. A Multifrequency Coastal HF Radar (MCR) was deployed for 10 days at two sites on the shore of Lake Michigan near St. Joseph, MI. Similarly, a single-frequency CODAR SeaSonde instrument was deployed on the California shore of Lake Tahoe. These two experiments showed that when sufficiently strong surface winds (2 about 7 m/s) exist for an hour or more, a single HE radar can be effective in measuring the radial component of surface currents out to ranges of 10-15 km. We also show the effectiveness of using HF radar in concert with acoustic Doppler current profilers (ADCPs) for measuring a radial component of the current profile to depths as shallow as 50 cm and thus potentially extending the vertical coverage of an ADCP array.

The Flying Fish Persistent Ocean Surveillance Platform

*† ‡ § ** †† , The Flying Fish platform is an ocean, environmental monitoring buoy that repositions as an Unmanned Aerial System (UAS), maintaining a pre-set watch circle. To operate in the open ocean, the platform must be robust to moderate sea state conditions and must function unattended thus fully-autonomously. Our concept was conceived as an alternate solution to surface boat designs, avoiding the hydrodynamic drag of ocean waves and currents while in flight. Over the first project year, we developed and repeatedly demonstrated our prototype vehicle’s ability to autonomously “hop” across a GPS-defined “watch circle”, providing initial validation of the unified UAS-buoy (air/sea vehicle) persistent ocean monitoring concept. This paper will describe the vehicle design and performance characterization through simulation and flight-testing and provide insight to the Phase II vehicle which will operate for long periods with a balanced energy budget.

Radar backscatter from mechanically generated transient breaking waves. II. Azimuthal and grazing angle dependence

For Pt. I see ibid. vol. 26, pp. 181-200 (2001). This paper describes the results of experimental investigations into the microwave backscatter from mechanically generated transient breaking waves. The investigations were carried out in a 110 m/spl times/7.6 m/spl times/4 m deep model basin, utilizing chirped wave packets spanning 0.75-1.75 Hz. Backscatter measurements were taken by a K-band continuous wave radar (24.125 GHz) at 40/spl deg/ angle of incidence, and at azimuth angles of 0/spl deg/, 45/spl deg/, 90/spl deg/, 135/spl deg/ and 180/spl deg/ relative to the direction of wave propagation. Grazing measurements were conducted using an X-band (10.525 GHz) FMCW radar at 85/spl deg/ angle of incidence, and azimuth angles of 0/spl deg/ and 180/spl deg/. Results show that the maximum radar backscatter was obtained in the upwave direction prior to wave breaking and was caused by the specular or near specular presentation of the wave to the radar. After breaking, the backscatter transitioned from a specular or near-specular dominated scattering, primarily seen in the upwave direction, to a small scale roughness dominated scattering, observed at all azimuths. Physical optics solutions were found to correctly predict the backscatter for the specular or near-specular dominated scattering and the small perturbation method was found to accurately model the VV polarization post-break radar backscatter.

Using multifrequency HF radar to estimate ocean wind fields

HF radar has become an important tool for mapping surface currents in the coastal ocean and has been used to determine wind direction. Here the author investigate further the ability of multifrequency HF radar to measure the vector wind field and the impact that such measurements have on the measurement of coastal wind fields over both the land and sea. In this study the author use data collected over Monterey Bay, California from Jan. to Aug. 2001. Their multifrequency coastal radars (MCRs) operated at 4.8, 6.8, 13.4 and 21.8 MHz, measuring currents at effective depths of about 2.5, 1.8, 0.9 and 0.6 m respectively. Here, the author move beyond their preliminary reports by examining the durability of their HF wind vector measurements over a seven-month data set. The results over this longer time span indicate standard errors of prediction (SEPs) of 1.2 and 1.1 m/s for the U and V wind speed components respectively with biases less than 0.15 m/s. The author also investigate a Kalman filtering modification to their partial least squares algorithm. Further, the author demonstrate the beneficial impact of multifrequency HF radar, wind field measurements, on estimation of the coastal wind field over both land and sea.

Vernal thermal fronts in large lakes: A case study from Lake Michigan

Many temperate large lakes of the world undergo a transition in the spring from fully mixed winter conditions to thermally stratified summer conditions (RODGERS 1966, TIKHOMIROV 1963). That transition often includes the formation of a well defined front characterized by a nearly vertical, shore-parallel 4 O C isotherm (SAYLOR et al. 1981). This front, which is maintained by a convergent secondary circulation and accompanied by geostrophic currents, induces a significant redistribution of heat and other properties in the coastal waters (BENNETT 1971, ROUSAR 1973). Many vernal thermal fronts are characterized by large chemical and biological gradients (SCAVIA 8; BENNETT 1980). The current state of knowledge of vernal thermal fronts in large lakes is largely based on theoretical studies that are relatively unconfirmed by field observations. Given this state of knowledge, our study group elected to begin a multidisciplinary, multiyear study of vernal thermal fronts in southeastern Lake Michigan. The point of departure for this study was the theoretical framework of water circulation in the vicinity of vernal fronts developed by HUANG (1969, 1972) and MORTIMER (1974, 1988). The purpose of this paper is to provide an overview of the results from five field seasons of study (1988 to 1992) of the Lake Michigan vernal thermal front.

LAGRANGIAN VELOCITY PROFILES IN THE WAKE OF A HIGH SPEED VESSEL

Abstract A video imaging technique is employed in a towing basin to obtain high resolution surface Lagrangian velocity observations in the centerline wake region of a high speed, twin screw surface vessel. Approximately 30,000 surface velocity realizations within the wake region extending from the stern to approximately six model ship lengths aft are used for comparison with both recent full-scale and numerical model results. Analysis of this data set reveals spatial decay rates in the mean and fluctuating velocity components which serve to identify relevant scales of motion and define candidate mechanisms for the persistence of these wakes in remotely sensed ocean surface data.

Drawing Lines in Law Books and on Sandy Beaches: Marking Ordinary High Water on Michigan's Great Lakes Shorelines under the Public Trust Doctrine

In 1968 the Michigan Legislature adopted an elevation-based approach for discerning the ordinary high water mark (OHWM) along the states Great Lakes shorelines pursuant to the public trust doctrine. In 2005 the Michigan Supreme Court reaffirmed that Michigans public trust interest extends up to the OHWM, but it articulated a different standard for discerning that OHWM, noting in passing that the states statutory standard relates only to certain regulatory authorities. The court left unresolved the questions of exactly how these two methods of marking ordinary high water relate to one another and precisely how far up the shore the states authorities to regulate private shoreline development extends. We first describe how the Great Lakes states, including Michigan, have adapted the public trust doctrine to their Great Lakes shorelines, particularly in terms of demarcating boundaries. We then discuss attributes of the Great Lakes that make those efforts problematic and present original data on changing water levels and shoreline profiles along Lake Michigan over time. Based on that analysis, we conclude that while use of an OHWM on Great Lakes shorelines makes sense, the states statutory elevation-based OHWM standard makes little sense given Great Lakes shoreline dynamics. We identify further legal and policy issues the state will likely confront as it attempts to mark OHW in the foreseeable future given both the state of the law and the nature of the Great Lakes.

Surface current observations by HF radar during EEGLE 2000

HF radar has become an important tool for mapping surface currents in the coastal ocean. However, its use over fresh water has been limited due to much higher propagation loss and smaller wave heights on fresh water lakes. During the Episodic Events Great Lakes Experiment (EEGLE) two multifrequency coastal radars (MCRs), operating between 4.8 MHz and 21.8 MHz, were installed on the southeast shore of the lake, together with an air-sea measurement buoy. Data from the February-April 2000 observations demonstrate HF radar performance characteristics over fresh water as well as characteristics of the surface flow in the lake during periods of moderate to high winds and waves. In early April an episodic event occurred in which strong northerly winds blew down Lake Michigan driving currents down the western shore of the lake past Racine, Wisconsin and Chicago, Illinois and around the southern lake shore to the southeastern shore of the lake. Sediments are resuspended during such an event, putting a variety of pollutants in the water column. These suspended sediments are clearly shown in visible light images from the NOAA-14 satellite. HF radar and buoy measurements of an episodic resuspension event are presented. They show a southward surface current flow at the beginning of the event and then a reversal of the near-shore current as the event progresses and the aforementioned currents move around the bottom of Lake Michigan and reach the St. Joseph, Michigan area. These observations show the interplay of large scale currents from the south and local wind driven currents.