Buhne Point, Humboldt Bay, California: Design for the Prevention of Shoreline Erosion: Hydraulic and Numerical Model Investigations

Source: https://erdc-library.erdc.dren.mil/jspui/Two numerical models and two physical models were used to investigate the effects of proposed improvement plans with respect to shoreline erosion at Buhne Point, Humboldt Bay, California. Initially, a numerical tidal circulation model was used to determine the tidal current field adjacent to Buhne Point. Maximum flood and ebb tidal currents were identified and used as test conditions for the physical models. A 1:100-scale physical model of central Humboldt Bay included the jettied entrance to the bay, approximately 18,000 lin. ft of shoreline inside the bay (including Buhne Point), and underwater contours throughout the central portion of the bay and the area between the jetties . This model was used to determine the wave climate (angle of wave fronts and wave heights along these fronts) in the vicinity of Buhne Point for a series of incident wave conditions and directions (waves propagated through the Humboldt Bay entrance) and for various water levels and tidal flow conditions. A 30-ft-long wave generator, an Automated Data Acquisition and Control System (ADACS), and a model circulation system were utilized in model operation. The output conditions obtained from the 1:100-scale physical model were input lnto a 1:50-scale physical model of Buhne Point where the effectiveness of various structures proposed for shore protection was evaluated. This model reproduced approximately 9,200 lin. ft of shoreline in the Buhne Point area and the immediate underwater contours in Humboldt Bay and utilized an 85-ft-long curved wave generator, a model circulation system, and crushed coal tracer material in model operation. Through the use of a numerical sediment transport model of Humboldt Bay, the effects of the optimum improvement plan developed from the 1:50-scale physical model on conditions (sediment movement, tidal flushing, etc.) in other areas in the bay (areas not included in the physical models) were determined. The numerical tidal circulation model provided the tidal current field adjacent to Buhne Point for existing (1983) conditions and for the optimum improvement plan (Plan 30) . Based on the results of this model investigation, it was concluded that changes in tidal current velocities and flow patterns will be minimal due to the proposed improvements. The 1:100-scale physical model of central Humboldt Bay provided the wave front and wave heights along the front in the vicinity of Buhne Point for test waves for five water levels and from three directions. Based on the results of this model investigation, it was concluded that: (A.) Regardless of the direction of incident wave approach from the Pacific Ocean, the angle of the wave front in the vicinity of Buhne Point remains essentially the same. (B.) Test waves from northwest (approaching through the Humboldt Bay jettied entrance almost directly up the axis of the channel) result in significantly larger wave heights in the vicinity of Buhne Point, as opposed to test waves from north and/or west. The 1:50- scale physical model of Buhne Point was used to determine the cliuses of erosion at the point and the effectiveness of various structures proposed for shore protection. Based on the results of thls model investigation it was concluded that : (A.) Wave energy approaching Buhne Point from the jettied entrance to Humboldt Bay resulted tn erosion of the original spit. Sediment eroded from the eastern portion of the shoal and migrated westerly where it entered the navigation channel. (B.) For the originally proposed improvement plan (Plan 1), erosion occurred at the eastern portion of the fill with accretion against the proposed groin. Eventually, material migrated around the groin head and toward the nlivigation channel. (C ). For the proposed groin plan (Plan 2), the shoreline did not remain stable. Sediment eroded at the eastern portion of the fill and accreted against the originally proposed westernmost groin. Material eventually migrated around the groin head and toward the navigation channel. (D.) Sediment eroded in the lee of the shore-connected breakwater with the +7 ft elevatlon (Plan 3) for normal high-tide conditions (water el +6.7 ft). (E.) Sediment remained stable in the lee of the shore-connected breakwater with the +10 ft elevatlon (Plan 3A) for normal tide conditions (water el +6.7 ft), but erosion occurred for extreme hightide conditions (water el +9.5 ft). (F.) Sediment remained stable in the lee of the shore-connected breakwater with the +13 ft elevation (Plans 3C and 3D) for all tide conditions (inclurling the extreme +9.5 ft conditions). (G.) A reverse curve in the shore-connected breakwater where it originates from the existing Buhne Drive revetment (Plan 3D) minimized wave convergence and runup in this area. (H.) A 25-ft-wide fill (el +12 ft) in the lee of the shore-connected breakwater lind adjacent to the existing Buhne Drive revetment (Plan 30) prevented transmitted wave energy from running up on Buhne Drive for all test conditions. (I.) Erosion occurred in the lee of the offshore breakwater plans with the +13 ft elevation (Plans 4 and 4A) for extreme high-water conditions (water el +9.5 ft). When the fill was depleted, wave energy transmitted through the revetment adjacent to Buhne Drive and onto the roadway. (J.) A 1,000-ft-long offshore breakwater with the eastern 425-ft portion installed at a crest elevation of +16 ft (Plan 4B) was required to stabilize the fill in the lee of the structure. Slight erosion of the fill at its eastern limit occurred prior to stabilization, but wave runup onto Buhne Drive did not occur. (K.) A 1,200-ft-long offshore breakwater with the eastern 625-ft portion installed at a crest elevation of +16 ft (Plan 4F) resulted in a stable shoreline in the lee of the structure with no erosion. (L.) Sediment stabilized and remained in the area between the structures with the 425- ft-long extension of the original groin for all test waves, tidal currents, and water levels. (M.) Small amounts of sediment penetrated through the voids of the rubble groin head at the downcoast (western) end of the fill for extreme high-tide conditions (water level +9.5 ft). (N.) Of the improvement plans tested, Plan 3D was regarded as the optimum, considering shore protection and construction costs. The shoreline remained stable for all test waves, tidal flow conditions and water levels. The numerical sediment transport model (CELC3D) provided estimates of sediment movements due to residual tidal currents and wave interactions, for both the existing (1983) conditions and for improvement Plan 3D. From this investigation, it was concluded that no new sediment transport patterns are induced by the optimum improvement plan (Plan 3D). NOTE: This file is large. Allow your browser several minutes to download the file

Urban Form and Household Activity-Travel Behavior

Cities and metropolitan regions face several challenges including urban sprawl, auto dependence and congestion, and related environmental and human health effects. Examining the spatial characteristics of daily household activity-travel behavior holds important implications for understanding and addressing urban transportation issues. Research of this sort can inform development of urban land use policy that encourages the use of local opportunities, potentially leading to reduced motorized travel. This article examines the potential household activity-travel response to a planned metropolitan polycentric hierarchy of activity centers. Behavioral observations have been drawn from an activity-travel survey conducted in the Portland, Oregon, metropolitan area during the mid-1990s. Evidence presented from exploratory analysis indicates an urban/suburban differential, with less daily travel and smaller activity spaces for urban households. Investigation of the travel reduction potential of the proposed land-use strategy suggests that location effects could be offset by adjustments to household sociodemographic and mobility characteristics. Copyright 2006 Blackwell Publishing.

From medical to health geography: novelty, place and theory after a decade of change

In this paper, we reflect on the positioning of health geography within the wider academic landscapes of geography and health-related research. Drawing on examples from a number of countries, we consider the extent to which a ‘new geography of health’ has emerged in recent years. We structure our discussion around the themes of place, theoretical engagement and critical relevancy. Changes within the subdiscipline are placed in the context of a central question: what is new about the new geography of health

A dimensão espacial nos estudos sobre saúde: uma trajetória histórica The spatial dimension in health studies: a historical trajectory

Este artigo recupera as concepções de espaço incorporadas pela saúde pública entre final do século XVIII e meados do XX. É proposta uma padronização, com base na produção intelectual da área, iniciando-se com a apresentação da obra de Finke (1792), passando-se então à análise do século XIX, quando geografia e medicina se transformaram em disciplinas científicas. A concepção de espaço como ambiente físico, abstraído da ação humana - consolida-se no interior da geografia, enquanto na medicina prevalece o paradigma biológico-individual. Discute-se a importância da incorporação das noções geográficas de determinismo, gênero de vida e ecologia humana pela saúde pública e apresentam-se as contribuições de Max Sorré e Pavlovsky. Recupera-se a criação, em 1952, da Comissão de Geografia Médica de Saúde e Doença da União Geográfica Internacional e analisa-se o surgimento e a consolidação da New Geography.<br>Focusing on concepts taken from critical geography, this article re-examines the spatial notions that were incorporated by the public health field between the late eighteenth and mid-twentieth centuries. Based on a review and systematization of intellectual production within the field of medical geography, this time span is broken into periods. We begin with a presentation of Finke's work (1792) and then move on to analyze the nineteenth century, when geography and medicine became scientific disciplines. The concept of space as a physical environment, with human action abstracted out, took hold within geography, while the biological-individual paradigm prevailed within the field of medicine. The text discusses the implications of the public health field's decision to embrace the geographic notions of determinism, type of life, and human ecology, and describes the contributions of Max Sorré and Pavlovsky. It also looks at the International Geographical Union's 1952 creation of a Commission on the Medical Geography of Health and Illness and analyzes the emergence and coalescence of the 'new geography'