This article describes the testing and calibration of a digital video camera system used to measure surface moisture over a section of beach extending tens of metres alongshore using the brightness of the sand surface. The system consisted of two networked video cameras mounted on a mast on the foredune crest about 14 m above the beach surface and oriented obliquely alongshore in either direction. Photographs and video clips were stored on a notebook computer. Over a period of 4 weeks in May and June 2006, a series of field tests was carried out; these tests were designed to calibrate the surface brightness recorded at locations visible in the digital images against gravimetric surface moisture measured by scraping the surface at the same location. While there was a significant correlation between surface brightness and gravimetric moisture content, the strength of this relationship was improved by normalising against a white board present in the field of view of the camera. An even stronger relationship was obtained by normalising against an area of dry sand present within a portion of the photograph. Rectification of the images and application of the calibration equation permitted mapping of surface moisture variations on a timescale of hours to days. The approach appears to provide a useful means of estimating surface moisture on the beach on a scale of tens of metres and over timescales of seconds to months.
This paper reports on a remote sensing station specifically designed to investigate eolian processes at a beach–dune system. The monitoring station is located at Greenwich Dunes, Prince Edward Island National Park, Prince Edward Island (Canada), and it is the second, improved generation of a previous system using continuous video and photographs. The setup consists of three digital single-lens reflex cameras, a two-dimensional sonic anemometer, two safires, erosion–deposition pins, and an array of batteries and solar panels. The cameras run on a timer that takes pictures every hour. The images are rectified and analyzed using a combination of ArcMap 9.2 and PCI Geomatica software, which permits the generation of moisture maps, vegetation, ice and snow cover, shoreline position, and erosion–deposition processes. The two-dimensional sonic provides continuous wind speed and direction, and the saltation probes record the intensity of transport events. The result is a large geodatabase of a time series of factors affecting eolian processes at the beach at a variety of temporal and spatial scales. This geodatabase can be queried, and it is a valuable tool for studying the frequency and magnitude of events delivering sediment from the beach to the dune and thus for improving our knowledge of sediment transport at coastal areas. Although the remote sensing station was initially conceived as a tool to measure subaerial processes, a full year of measurements shows large potential for the system to provide information on processes at the nearshore environment and ice dynamics.
The geomorphology and stratigraphy of the Duchess dune field, in southeastern Alberta, provides a proxy record of the relationship between late Holocene paleoenvironmental conditions and eolian activity. Optical ages of eolian deposits show activity ca. 4500 to 2900 years ago and ca. 400 to 230 years ago, whereas combined radiocarbon and optical ages from sheet sand and paleosol sequences indicate dune stability ca. 980 to 400 years ago. Episodes of dune activity and stability were contemporaneous with peri-ods of increased aridity and increased moisture availability, respectively. Unlike the Great Sand Hills of southwestern Saskatchewan, there is no evidence of significant dune activity in the last 200 years, possibly due to the predominance of northwesterly winds providing greater moisture to this area.
Abstract Measurements of velocity and suspended sediment concentration were carried out in a saltmarsh tidal creek network in the Cumberland Basin, Bay of Fundy, Canada. The study area was located on the NW shore of the basin in part of an undyked marsh that is about 200 m wide with a simple reticulate creek network. The area is macrotidal with spring tides greater than 12 m and suspended sediment concentrations in the basin characteristically range from 150–300 mg l −1 . The purpose of the study was to determine vertical and along channel variations in these two parameters over individual tidal cycles and to use these data to assess the role of the tidal creeks in the import and export of water and sediment from the marsh surface. Measurements using a vertical array of co-located electromagnetic current meters and OBS probes for measuring suspended sediment concentration were carried out over four spring tides at a cross section in the lower part of Middle Creek. Six sets of measurements were carried out at four locations along the length of the creek, a distance of about 200 m over six tides ranging from spring to neap. Maximum mean velocities measured over sampling times of eight minutes did not exceed 0.1 m sec −1 in Middle Creek and 0.15 m sec −1 in Main Creek. Transient high velocities associated with the overbank flows were weakly developed as a result of the absence of significant levees or embankments on the marsh surface. Suspended sediment concentrations in the creek generally decreased steadily over the period of inundation. Flow across the marsh margin occurred simultaneously with the achievement of bankful conditions and the creeks themselves appear to play a relatively minor role in the movement of water and sediment onto and out of the marsh. Despite the fact that the marsh surface is still low in the tidal frame and active sedimentation is still occurring, the low flow velocities and observations in the field suggest that the tidal creek network is unable to flush itself and that it is contracting.
A seminal paper by Schumm and Lichty (1965, Am. J. Sci. 263; 110-119) was instrumental in demonstrating how a comprehensive and complete understanding of geomorphic systems necessitated deep knowledge about process-response dynamics across a range of temporal and spatial scales. Nevertheless, contemporary research that integrates knowledge across scalar domains remains surprisingly uncommon, perhaps because of methodological, theoretical, logistical, and pragmatic factors that inadvertently favor myopic perspectives on landform studies. A decade-long research agenda conducted on the north shore of PEI provides insights into major uncertainties associated with deploying process-based knowledge derived from plot (micro) scale experimentation on aeolian sediment transport across the beach-dune profile for the purpose of extrapolating to landform (meso) scale outcomes that are relevant to coastal resource managers. Results from short-term, instrumented experiments can only be understood within the broader context of the landform (meso) and landscape (macro) drivers and controls that mediate the potential range of short-term processes. For example, predicting the volume of sediment delivered to the foredune system annually is, to first order, dependent largely on the wind climatology and character of the beach sediments. However, long-term monitoring demonstrates that sediment delivery is also dependent on a much wider range of variables at the micro (e.g., moisture content, wind steering, turbulence production), meso (e.g., vegetation phenology, snow cover, fetch effects, nearshore sediment supply), and macro (e.g., sea-level rise, geological framework) scales. A proposed classification of system state variables is proposed for sandy beach-dune systems, predicated on the ideas of Schumm and Lichty (1965), that makes apparent some of these contextual inter-dependencies.
