Quantifying Human Impacts on River Bar Morphology Using Digital Photogrammetry

Historically, the study of fluvial geomorphology has been dominated by the field method of surveying using a level and surveying rod. Beginning in the 1980s, the use of ground based and aerial LiDAR increased in popularity as a surveying method. However, LIDAR is expensive and requires significant training to operate. In recent years there has been an increase in the applicability of digital photogrammetry in the field of fluvial geomorphology. Lower costs, streamlined training and an increased accuracy all make digital photogrammetry a promising tool for the field geomorphologist. A study of the morphologic changes of four river bars on the Browns Canyon section of the Arkansas River, Colorado is used to explore the potential of digital photogrammetry by attempting to quantify the impacts of recreation river users on bar morphology. By creating high resolution digital elevation models (DEMs) at time intervals from 24 hours to several days, DEMs of difference (DoDs) were created and analyzed using the open-source 3D data processing software CloudCompare. DoDs were correlated with historical, daily commercial river user data to derive a relationship. Verification concerning the validity of CloudCompare was done using a simple experiment simulating erosion and deposition of a known volume of material

Distribution, analysis, and recovery of fine gold from alluvial deposits

The United States Bureau of Mines, in its Heavy Metals Program, desired to have research performed to determine the size-frequency distribution and possible economic value of gold particles in the fine size ranges of Alaskan placer deposits. Primary interest was involved in obtaining evidence of the occurrence of fine gold and to determine the ameanability of standard sampling and production methods in the evaluation and recovery processes. A research contract between the United States Bureau of Mines and the University of Alaska was initiated in June, 1968 as the first phase of this investigation, but was subsequently modified in June, 1969 to include beneficiation processes amenable to recovery as well as evaluation methods for fine and flakey gold. In searching the literature relative to fine gold in Alaskan placer deposits, it was found that virtually no research has been devoted to determining the extent of fine gold distribution and its effect on evaluation and subsequent recovery methods. Standard evaluation techniques have relied on gravity methods of concentration and recovery of the visible gold from the concentrate. In general, this has proved satisfactory in that operational recovery methods used were probably not conducive to retaining gold particles of less than 100 mesh in size. Operators have made no attempt to obtain a size analysis of gold in a head sample, but many have kept records of the size distribution of the gold as actually recovered. A review of these records, from selected areas, indicates that the -100 mesh gold represents from 0 to 5% of the total gold recovered. Although figures of this type may point to a probably fine gold loss, the difficulties inherent in evaluating the tailng material or modifying the recovery system have usually discouraged efforts in this direction.This study was made possible by the Financial support of the United States Bureau of Mines through Research Contract No. HOl81009 with the University of Alaska

Limaria hians (Mollusca : Limacea): a neglected reef-forming keystone species

1. A key component of physical habitat along braided river systems is the exposed riverine sediment within the active zone. The relatively unmanaged, gravel-bed Fiume Tagliamento, Italy, provides the focus for exploring two ecologically important properties of exposed riverine sediments: their within-patch and between-patch variability in calibre. 2. To characterize between-patch variation in exposed riverine sediments, replicate (within-patch) samples were obtained from three geomorphologically distinct locations along 130 km of the river: bar heads along the margin of the low-flow channel, the heads of major bars across the exposed surface of the active zone, and floodplain surfaces. A photographic technique enabled rapid and consistent field sampling of the coarse sediments at bar heads along the low-flow channel margin and on major bars across the dry bed. 3. A downstream decrease in particle size and an increase in within-patch heterogeneity in sediment size were observed within bar head sediments along the margin of the low-flow channel. Comparisons between major bar and low-flow channel samples revealed greatest within-patch variability in individual sediment size indices (D50, A- and B-axes of the larger particles) at headwater sites, greatest between-patch variability in the three measured indices in the central reaches, and lowest between-patch variability at downstream sites. However, there was a distinct increase in the overall heterogeneity in particle size, which was sustained across all patches, in a downstream direction. 4. There was a clear downstream decrease in the size of floodplain sediments in the headwaters, but thereafter there was no distinct downstream trend in any of the calculated particle size indices. 5. The geomorphological controls on the observed patterns and the potential ecological significance of the patterns, particularly for plant establishment, are discussed in relation to the relative relief of the active zone, and the highly variable hydrological and climatic regime along the river

\u3cem\u3eLaunching through the Surf\u3c/em\u3e Traveling Exhibit Panel 02: Historical Highlights

The first of three panels in the exhibit that provide general historical highlights about the Dory Fleet, panel two features a timeline of events from 1855 to 1935. It incorporates a section from the Oregon House Calendar of 1927, chronicling the introduction and passage of House Bill 282. This legislation closed the Nestucca River to commercial fishing. The panel also includes an excerpt from the 1927 version of the Oregon Voters’ Pamphlet that describes an initiative to overturn the legislative action.https://digitalcommons.linfield.edu/dory_exhibit/1001/thumbnail.jp

\u3cem\u3eLaunching through the Surf\u3c/em\u3e Traveling Exhibit Panel 02: Historical Highlights

The first of three panels in the exhibit that provide general historical highlights about the Dory Fleet, panel two features a timeline of events from 1855 to 1935. It incorporates a section from the Oregon House Calendar of 1927, chronicling the introduction and passage of House Bill 282. This legislation closed the Nestucca River to commercial fishing. The panel also includes an excerpt from the 1927 version of the Oregon Voters’ Pamphlet that describes an initiative to overturn the legislative action.https://digitalcommons.linfield.edu/dory_exhibit/1001/thumbnail.jp

Prediction of hazardous Columbia River bar conditions

In this study methods were developed for the prediction of wave conditions that are hazardous to navigation at river entrances, with emphasis on applicability to the Columbia River. There are two basic components to the prediction system: (1) a semi-automated spectral method for forecasting the significant height and average period of waves in deep water, and (2) an index of navigation hazard at river entrances that depends on the significant height and average period in deep water and on the mean current and water depth at the entrance. The computerized, deep water forecast method is a hybrid scheme that combines the spectral principles of the Pierson-Neumann-James method with the graphical input techniques of Wilson and the fetch limited spectrum of Liu. The significant heights generated by the method are well verified by winter wave measurements at Newport, Oregon. The hazard index is based on the probability of wave-breaking in water of arbitrary depth and current. The breaking probability is derived under the assumption that wave heights and squared periods are statistically independent and distributed according to a Rayleigh probability density function. The breaking-wave probability and the hazard index depend on the wave steepness in deep slack water and on the depth (relative to the wave period squared) and current (relative to the period) at the river entrance. The dependence on depth and current is achieved in two ways: (1) the limiting steepness (breaking index) k found as a function of relative depth and relative current, and (2) the wave spectrum in water of arbitrary depth and current is found by transformation of the spectrum in deep slack water. The transformation is performed by requiring that the rate of wave energy propagation remain constant. The hazard index is closely related to the probability of breaking swell. At water depths that are typical of river entrances, the hazard index depends strongly on the significant wave height, mean current and depth, but only weakly on the mean wave period (since the breaking height of swell at such depths is only weakly dependent on period). Hindcasts of deep water significant wave heights and hazard indices compared reasonably well with measured heights and Columbia River bar closure periods. Forecasts based on accurate prognostic weather charts should provide similar results

The origin of beach sediments on the North Queensland coast

Petrographic and granulometric analyses of North Queensland beach sediments indicate their affinity with sediments delivered to the coast by rivers, and it is shown that the beaches are largely derived from fluvial sediment reworked, sorted and distributed by the dominant south-easterly waves in coastal waters. Beach sediments are generally quartzose, with subordinate felspars and admixtures of coralline sediment near fringing reefs and lithic material near river mouths and rocky shore sectors. The prevailing northerly drift of shore sediment is reduced, and locally reversed, on sectors sheltered from the dominant south-easterly waves by headlands, reefs and islands. Variations in beach sediment are related to wave conditions, distance from river-mouth sources, and patterns of drift. Four Mile Beach, near Port Douglas, is identified as anomalous in its morphological and sedimentological characteristics. It has been cut off from former sources of sediment, both fluvial and longshore, as a result of reef extension around the mouth of Mowbray River, and is now essentially a relict beach system attaining sedimentological maturity