James P. Bennett

Interparticle collision of natural sediment grains in water

Elastohydrodynamic theory and measurements of particle impacts on an inclined glass plane in water are used to investigate the mechanics of interparticle collisions in sediment-transporting flows. A collision Stokes number is proposed as a measure of the momentum of an interparticle collision versus the viscous pressure force in the interstitial gap between colliding particles. The viscous pressure force opposes motion of the particles on approach and rebound. A Stokes number of between 39 and 105 is estimated as the critical range below which particle impacts are completely viscously damped and above which impacts are partially elastic. The critical Stokes number is shown to roughly coincide with the Bagnold number transition between macroviscous and grain inertial debris flows and the transition between damped and partially elastic bed load transport saltation impacts. The nonspherical nature of natural particles significantly alters the motion of the center of mass after a partially elastic collision. The normal to the point of contact between the particles does not necessarily go through the center of mass. Thus normal rebound of the center of mass may not occur. A model of particle motion after rebound for particles of arbitrary shape, conserving both linear and angular momentum, is proposed.

SIMULATION OF SEDIMENT TRANSPORT AND ARMOURING / Simulation des transports solides et de l'armure du lit

Abstract A realistic sediment transport simulation model must incorporate an unsteady, non-uniform flow computation component, a means of simulating bed load and suspended sediment transport and their interactions, and bed armouring and elevation accounting routines. A model embodying these components has been developed for upland streams with tributaries. The streams are assumed to have a wash load, sand or gravel beds, and erosion resistant banks. After calibration of the model using 15 days of data collected during the spring of 1975 from sections of the East Fork River in Wyoming and its tributary Muddy Creek, a standard error of prediction of 50 per cent of the average observed bed load discharge of 3.43 lb/s (1.55 kg/s) was obtained. The total bed load outflow for the simulation period was 20 per cent greater than that obtained from bed load discharge measurements and 94 per cent greater than a rough estimate of volumetric change obtained from observations of bed elevations. A fortunate characterist...

Effect of discharge on the chlorophyll a distribution in the tidally-influenced Potomac River

In the tidal Potomac River, high river discharges during the spring are associated with high chlorophylla concentrations in the following in the following summer, assuming that summertime light and temperature conditions are favorable. Spring floods deliver large loads of particulate N and P to the tidal river. This particulate N and P could be mineralized by bacteria to inorganic N and P and released to the water column where it is available for phytoplankton use during summertime. However, during the study period relatively low concentrations of chlorophylla (less than 50 μg l−1 occurred in the tidal river if average monthly discharge during July or August exceeded 200 m3s−1. Discharge and other conditions combined to produce conditions favorable for nuisance levels of chlorophylla (greater than 100 μg l−1 approximately one year out of four. Chlorophylla maxima occurred in the Potomac River transition zone and estuary during late winter (dinoflagellates) and spring (diatoms). Typical seasonal peak concentrations were achieved at discharges as high as 970 m3 s−1, but sustained discharges greater than 1,100 m3 s−1 retarded development. Optimum growth conditions occurred following runoff events of 10 to 15 d duration which produced transit times to the transition zone of 7 to 10 d. Wet years with numerous moderate-sized runoff events, such as 1980, tend to produce greater biomass in the transition zone and estuary than do dry years such as 1981.

16-year trends in elements of lichens at Theodore Roosevelt National Park, North Dakota.

An epiphytic lichen and a soil lichen in two very closely related genera (Parmelia sulcata and Xanthoparmelia chlorochroa, respectively) were sampled 16 years apart at Theodore Roosevelt National Park in North Dakota and measured for their elemental content. Mercury and cadmium decreased approximately 30% over the time period in both species. Sulfur decreased 8% in the epiphytic species, but increased 20% in the soil lichen. Factor analysis revealed that soil elements were higher in the soil lichen, indicating there was some soil contamination in that species. A relationship between iron and titanium was found only in the soil lichen. Sulfur and mercury were highly enriched in both species relative to the soil, which suggests that the atmosphere is a contributing source of these elements. New baseline values were calculated, 22 elements for both species, although it is not recommended that the soil lichen be sampled in the future.

Copper localization, elemental content, and thallus colour in the copper hyperaccumulator lichen Lecanora sierrae from California

An unusual dark blue-green lichen, Lecanora sierrae , was discovered over 30 years ago by Czehura near copper mines in the Lights Creek District, Plumas County, Northern California. Using atomic absorption spectroscopy, Czehura found that dark green lichen samples from Warren Canyon contained 4% Cu in ash and suggested that its colour was due to copper accumulation in the cortex. The present study addressed the hypothesis that the green colour in similar material we sampled from Warren Canyon in 2008, is caused by copper localization in the thallus. Optical microscopy and electron microprobe analysis of specimens of L. sierrae confirmed that copper localization took place in the cortex. Elemental analyses of L. sierrae and three other species from the same localities showed high enrichments of copper and selenium, suggesting that copper selenates or selenites might occur in these lichens and be responsible for the unusual colour.

Prion protein degradation by lichens of the genus Cladonia

It has recently been discovered that lichens contain a serine protease capable of degrading the pathogenic prion protein, the etiological agent of prion diseases such as sheep scrapie and cervid chronic wasting disease. Limited methods are available to degrade or inactivate prion disease agents, especially in the environment, and lichens or their serine protease could prove important for manage- ment of these diseases. Scant information is available regarding the presence or absence of the pro- tease responsible for degrading prion protein (PrP) in lichen species and, in this study, we tested the hypothesis that PrP degradation activity in lichens is phylogenetically-based by testing 44 species of Cladonia lichens, a genus for which a significant portion of the phylogeny is well established. We cate- gorized PrP degradation activity among the 44 species (high, moderate, low or none) and found that activity in Cladonia species did not correspond with phylogenetic position of the species. Degradation of PrP did correspond, however, with three classical taxonomic characters within the genus: species with brown apothecia, no usnic acid, and the presence of a cortex. Of the 44 species studied, 18 (41%) had either high or moderate PrP degradation activity, suggesting the protease may be frequent in this genus of lichens.

CALIBRATION OF BRANCHED ESTUARY MODELS

A series of wave basin experiments were undertaken to better understand the selection of groin spacings and lengths. Rather than obtaining edge waves with the same period as the normal incident waves, subharmonic edge waves were produced with a period twice that of the incoming waves and a wave length equal to the groin spacing. Rip currents were therefore not formed by the interactions of the synchronous edge waves and normal waves as proposed by Bowen and Inman (1969). Rips were present in the wave basin but their origin is uncertain and they were never strong enough to cause beach erosion. The generation of strong subharmonic edge waves conforms with the work of Guza and Davis (1974) and Guza and Inman (1975). The subharmonic edge waves interacted with the incoming waves to give an alternating sequence of surging and collapsing breakers along the beach. Their effects on the swash were sufficient to erode the beach in some places and cause deposition in other places. Thus major rearrangements of the sand were produced between the groins, but significant erosion did not occur as had been anticipated when the study began. By progressively decreasing the length of the submerged portions of the groins, it was found that the strength (amplitude) of the edge waves decreases. A critical submerged groin length was determined whereby the normally incident wave field could not generate resonant subharmonic edge waves of mode zero with a wavelength equal to the groin spacing. The ratio of this critical length to the spacing of the groins was found in the experiments to be approximately 0.15 to 0.20, and did not vary with the steepness of the normal incident waves. CICESE, Av. Gastelum No. 898, Ensenada, Baja California, Mexico. School of Oceanography, Oregon State University, Corvallis, OregonA significant portion of the damage by hurricanes is the storm surges. The National Weather Service has developed a dynamical-numerical model to forecast hurricane storm surges. The model is used operationally for prediction, warning, and planning purposes. The model requires fixed oceanographic and real time meteorological input data. The oceanographic data were prepared for the Gulf and East coasts of the U.S. and are stored as an essential part of the program. Meteorological data for any tropical storm are supplied by the forecasters or planners using the model. The model was applied to hurricane Camille 1969. Comparison between the observed and computed surges for Camille was satisfactory for prediction purposes.The main consideration in harbor master planning is to maximize the amount of time that the harbor can be used. The potential level of harbor utilization can be evaluated by analyzing vessel performance during harbor operations in terms of the range of imposed environmental conditions. The harbor utilization level is expressed statistically as the probable amount of time that the harbor can be used as planned.The purpose of this paper is to discuss the new manual titled Small Craft Harbors: Design, Construction and Operation, published by the D. S. Army Corps of Engineers Coastal Engineering Research Center (CERC) as Special Report No. 2 dated December 1974. The objective of the manual is to enable anyone with a basic engineering background to plan and design small craft harbors or do so with the help of one or more specialists. The manual outlines methods of investigating the problems involved and the various engineering, economic and environmental criteria to be applied. It covers much of the planning and design considerations discussed by the A.S.C.E. Committee on Small Craft Harbors in manuals and reports on engineering practice, #50, Report on Small Craft Harbors 1969. However, it also incorporates a considerable amount of additional information in the form of special design and construction techniques, certain rules of thumb commonly accepted in marina design practice, and observations as to elements of good practice in this field. It provides a compendium of planning data gleaned through a nationwide canvassing of marina operators, marina design engineers, and trades people who provide commonly used marina construction products. Also included in the manual are some of the design and construction requirements of various Federal, state and local government agencies having jurisdiction over, or assisting with the development of small craft harbors.The design and construction of a major ocean outfall and diffuser system for disposal of wastewater effluents is a complex process involving an interplay of requirements originating from various disciplines. These include, among others, considerations of physical oceanography, mixing and dispersion, treatment processes, regulatory requirements, marine geology, economics and construction. The recently completed Sand Island Outfall and the newly designed Barbers Point Outfall are both on the southern coast of the island of Oahu, Hawaii, and are designed for treated sewage effluents from the densely populated portion of the City and County of Honolulu. In this paper, some design considerations of these outfalls will be examined. The emphasis in this paper is on the hydrodynamics, although other design aspects are also discussed briefly.The height of dikes and other coastal structures can only be calculated after determination of the wave run-up. Several formulas for the calculation of wave run-up are developed after model tests as a rule. But the influences of scale effects and natural wind conditions are practically unknown. To clear these questions further investigations and especially field measurements should be carried out. By measuring the markerline of floating trash on the slope of the seadikes the maximum wave run-up could be found out after four storm surges in 1967 and 1973In two graphs it will be shown that on the tidal flats the run-up depends on the waterdepth. The run-up was higher than it could be expected after model tests of 1954. With a newly developed special echo sounder the run-up could be measured in January 1976. The waves and the run-up could be registrated synchronously during two severe storm surges. As shown in Fig. 9 it was found a logarithmic distribution of the wave height, wave period and the higher part of the wave run-up. The found wave run-up is considerably higher than estimated before. The measured 98 % run-up is found about twice the computed value. That is an interesting and important result of the first synchronous recording of wave run-up on sea dikes.These conditions are contradictory. Harbour mouthes are lateral enlargements. The current doesnt follow these enlargements, a separation sheet forms which is characterized by eddies. A more or less great mass of water is in movement in the enlargement. These rotating movements are called vortices. One distinguishes primary vortices, secondary vortices etc. depending on the initiating current (Fig. 1). The deposition of sediment in lateral enlargements depends on the characteristics of the vortices, because the exchange of liquid, material has interacted, with the exchange of transported, material. Normally the coarse material deposits in area a and. the fine material in area b (Fig. 1 ) , c Primary vortexBayocean Spit, separating Tillamook Bay from the Pacific Ocean on the northOregon coast, underwent severe erosion following construction of a north jetty at the bay entrance in 1914-17. This erosion ultimately led to the complete breaching of the spit in 1952. Simultaneous to the spit erosion south of the entrance, the shoreline north of the north jetty advanced seaward by some 600 m (2000 ft). This pattern of erosion and deposition following jetty construction has generally been interpreted as the jetty blocking a large north to south net littoral drift in the area, estimated by a previous study at 620,000 m/yr (800,000 yd/yr). Our reexamination of the shoreline changes and patterns of erosion and deposition following jetty construction disagrees with this interpretation, and instead we conclude that all of the changes resulted from local rearrangements of the beach due to the disrupted equilibrium following jetty construction, but at the same time maintaining an overall condition of zero net littoral drift. This interpretation is supported by other evidence that indicates a near-zero net drift on this portion of the Oregon coast. Thus severe coastal erosion can result from jetty construction even in areas of zero net littoral drift. A new south jetty has been recently completed (1974). The result has been further realignments of the shoreline with accretion and shore-: line advance immediately south of the south jetty. This provides further confirmation that a zero net littoral drift exists in the area. This study also demonstrates the effects of building only a single jetty rather than a pair of jetties. Following construction of the north jetty, the outer bar or ebb-tide delta at the Tillamook Bay inlet grew appreciably in size. Sand deposited there came from erosion of Bayocean School of Oceanography, Oregon State University, Corvallis, Oregon 97331. department of Geography, Western Washington State College, Bellingham, Washington 98225.In March 1972 the authors firm in association with two Portuguese firms of consulting engineers, Consulmar and Lusotecna, were appointed by the Portuguese Government agency Gabinete da Area de Sines to prepare designs for the construction of a new harbour at Sines on the west coast of Portugal. The location is shown in Figure 1. The main breakwater, which is the subject of this paper, is probably the largest breakwater yet built, being 2 km long and in depths of water of up to 50 m. It is exposed to the North Atlantic and has been designed for a significant wave height of 11 m. Dolos units invented by Merrifield (ref. 1) form the main armour. The project programme required that studies be first made of a wide range of alternative layouts for the harbour. After the client had decided on the layout to be adopted, documents were to be prepared to enable tenders for construction to be invited in January 1973. This allowed little time for the design to be developed and only one series of flume tests, using regular waves, was completed during this period. Further tests in the regular flume were completed during the tender period and a thorough programme of testing with irregular waves was commenced later in the year, continuing until August 1974 when the root of the breakwater was complete and the construction of the main cross-section was about to start. The model tests, which were carried out at the Laboratorio Nacional de Engenharia Civil in Lisbon, were reported by Morals in a paper presented to the 14th International Coastal Engineering Conference in 1974. (ref. 2)Estuaries may be sequentially classified into highly stratified, moderately mixed and vertically homogeneous. An important difference between moderately stratified or vertically homogeneous estuaries, and highly stratified estuaries (salt wedges) is that, in the former, tidal currents are sufficient to cause turbulent mixing of fresh water and sea water over the full depth of the estuary. In the latter, a distinct interface or interfacial layer exists which separates the two nearly homogeneous layers. The vertical advectlon of salt in this two-layer flow is the dominant process in maintaining the salt balance. This paper presents an analytical model describing this process. Experiments have been conducted in the laboratory to compare with the developed theory.Laboratory data showing the influence of planform geometry on the tidal flushing characteristics of small harbors of simple surface shape. The tide ranges, water depths, and planform areas are typical of those encountered in small-boat marinas in Puget Sound, Washington. Each harbor investigated had a single, asymmetric entrance. Flushing and circulation patterns within such harbors depend strongly upon the characteristics of the angular momentum established within the basin and upon the effective penetration distance into the basin of the stream of ambient water entering the harbor on the flood tide. Experimental results confirm that best gross tidal flushing occurs when rectangular harbors have an aspect ratio L/B near unity, and that rounding interior corners of the basin has little effect on the gross tidal flushing but does improve local exchange. Aspect ratios L/B less than 3 lead to the creation of more than one circulation cell (gyre) within the basin. INTRODUCTION This paper reports on a laboratory study of tide-induced circulation in small, constructed harbors. Effects of wind and waves upon water motions within the harbors are not considered. The study was keyed to the continuing demand for more small-boat marinas in Puget Sound, Washington. A common construction approach is to dredge the marina basin from a tideflat area, with the dredged material providing fill for parking lots, dry land work and storage areas, etc. A breakwater is provided on the seaward side, usually with a single asymmetric entrance located to provide best wave protection. Surface areas typically range from 10 to 30 acres, with provisions for from 200 to 800 boat moorages. Such marinas can truly be classified as small harbors. Questions related to water quality are of considerable importance in 1. Professor of Civil Engineering, University of Washington, Seattle, Washington, U.S.A. 2. Graduate Student, Department of Civil Engineering, Imperial College, London, Great Britain. 3. Technical Official, Civil Engineering Research Iestitute of Hokkaido Development Bureau, Sapporo, Japan.