Geography

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Start date: 1980End date: 1999

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    Washington, D.C. and the Growth of Its Early Suburbs : 1860-1920
    (1980) Levy, Anneli Moucka; Groves, Paul A.; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    During the nineteenth century, the North American city greatly changed in size and internal structure. With the introduction of mass transportation, large scale suburbanization took place as one aspect of this change. Members of the evolving middle class not only wished to escape the pollution and congestion of the urban core, but also believed strongly in a 'rural ideal,' translated into a 'suburban ideal.' Urban changes and suburban growth were especially pronounced in industrial cities, and descriptions of conditions in these cities identify the accepted model of the spatial configuration of the metropolis existed in 1920. Examination of the growth of Washington D. C. between the Civil War and World War I indicates that the city shared few of the characteristics of the accepted urban model. Nevertheless, it exhibited distinct suburban movement connected with three major transport modes, including the steam railroad. The belief in the 'suburban ideal' was broadly based in Washington and therefore much variation was found among the city's suburban communities, even among those associated with the same transportation mode. Furthermore, in contrast to the suburban model, conditions in the suburban areas often did not compare favorably with those in the city. Even so, the suburbanization process accelerated from small beginnings, so that by 1920 the city displayed the local variant of the typical star-shaped pattern.
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    Island Land Loss in the Chesapeake Bay: A Quantitative and Process Analysis
    (1992) Wray, Rachel Donham; Leatherman, Stephen P.; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    The rates and processes of land loss were studied for seven islands in the Chesapeake Bay: Barren, Bloodsworth, Hooper, James, Poplar, Smith and South Marsh Islands. Rates and patterns of land loss were quantified for the years 1848 to 1987 with the Metric Mapping technique which utilizes digitized data from historical maps and vertical aerial photographs. Processes of land loss were determined through field surveys and correlated with environmental factors. Two distinct island types were identified which exhibited different, long-term patterns of land loss. Small, upland islands, termed the Northern Group, showed rapid land loss along the main stem of the Bay primarily due to wave action driven by the predominant westerly winds. Land loss appeared to accelerate during periods of high storm frequency. The long-term averaged land loss rate for Northern Group islands is 1.9 ha/yr. The averaged erosion rate on the western side of the islands is 4.9 m/yr, compared to 0.68 m/yr on the eastern side of the islands. In contrast, the large, marshy islands of the Southern Group experienced uniform marsh edge erosion and interior marsh degradation. The Southern Group islands lost land at an averaged rate of 5. 6 ha/yr, with an averaged rate of marsh edge erosion of 1.2 m/yr. Land loss appeared to be weakly correlated to storm frequency. Interior marsh loss was not quantified for this study, however, so this study provides an underestimation of total land loss of coastal wetlands.
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    THE USE OF NARROW SPECTRAL BANDS FOR IMPROVING REMOTE SENSING ESTIMATIONS OF FRACTIONALLY ABSORBED PHOTOSYNTHETICALLY ACTIVE RADIATION
    (1994) Kim, Moon Sung; Townshend, John R.G.; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    Most remote sensing estimations of vegetation variables such as leaf area index (LAI), absorbed photosynthetically active radiation (Apar,), and primary production are made using broad band sensors with a bandwidth of approximately 100 nm. However, high resolution spectrometers are available and have not been fully exploited for the purpose of improving estimates of vegetation variables. The study was directed to investigate the use of high spectral resolution spectroscopy for remote sensing estimates of f apar in vegetation canopies in the presence of nonphotosynthetic background materials such as soil and leaf litter. A high spectral resolution measure defined as the chlorophyll absorption ratio index (CARI) was developed for minimizing the effects of nonphotosynthetic materials in the remote estimates of f apar CARI utilizes three bands at 550, 670, and 700 nm with bandwidth of 10 nm. Simulated canopy reflectance of a range of leaf area index (LAI) were generated with the SAIL model using measurements of 42 different soil types as canopy background. CARI calculated from the simulated canopy reflectance was compared with the broad band vegetation indices such as normalized difference vegetation index (NDVI), soil adjusted vegetation index (SAVI), and simple ratio (SR). CARI reduced the effect of nonphotosynthetic background materials in the assessment of vegetation canopy f apar more effectively than broad band vegetation indices.
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    Historical Shoreline Changes in Response to Environmental Conditions in West Delaware Bay
    (1990) French, Gregory T.; Leatherman, Stephen
    This study quantified historical changes in the coastline of the west shore of Delaware Bay. Shoreline changes were measured through the compilation of historical maps and photographs utilizing the Metric Mapping technique. These changes were correlated with various environmental conditions and with human influences. The results portray a 135 year pattern of overall erosion, with long-term rates averaging -4.5 ftjyr, which is considerably greater than the u.s. Atlantic coast average. Coastal engineering (e.g., groins, jetties and beach nourishment) were locally effective in reducing erosion rates and in some cases promoting limited accretion. Perhaps more importantly, there were few associated negative effects alongshore suggesting that various forms of coastal engineering can be effective in a low-energy environment, even when done in a somewhat unorganized fashion. A correlation was found between erosion rates and underlying Pleistocene morphology. Where pre-Holocene sediments were exposed in the nearshore, erosion rates were lower. However, erosion rates were substantially higher along marshy shorelines. This erosion is not continuous either spatially or temporally, but instead is largely storm-driven. Periods of relative quiescence corresponded with lowered rates of average annual shoreline recession. With the exception of the northernmost marshy areas, severe erosion occurs along all shorelines, regardless of morphology, in response to major coastal storms.
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    RECONSTRUCTION OF A DOWNTOWN: THE AFTERMATH OF THE GREAT BALTIMORE FIRE OF 1904
    (1993) Wingo, Amanda Jean; Groves, Paul; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    Reconstruction following a major disaster has farreaching impacts which can alter the functioning of a city. Understanding this process is therefore vital. The results of such a study add to the small body of literature on reconstruction following disaster and thus provides additional testing of the findings of Bowden(l967), the critical piece of literature on reconstruction to date. Specifically, this thesis considers the process of reconstruction by looking at the structural and spatial changes predicted by one catastrophic event. Using both Sanborn Atlases and Baltimore Business Directories between 1902 and 1914, the Central Business District (CBD) is examined through the analysis of concentration, sequencing, and persistence processes. More important, however, is the extent to which these processes impact the spatial characteristics of establishments within the Burnt District over a specific period of time (1902- --- ·--·-- 1914). A significant finding indicates that in the pre- and post-fire period Baltimore maintains a high degree of consistency within the Burnt District. However 1 the vertical dimension of Baltimore changes drastically from 1902 to 1914 allowing an increase in the availability of space explained by the vertical growth of buildings. The sequence of return of the "building block" establishments occurred within a surprising two years following the fire. Several defining situations fix or anchor establishments to their locations 1 which act to mitigate the variations in land-use patterns over time. The findings of this study provide a spatial view of the functional districts which play an important role in the life of the CBD of Baltimore.
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    Calculation of the Angular Radiance Distribution for a Coupled Atmosphere and Canopy
    (Institute of Electrical and Electronics Engineers, 1993-03) Liang, Shunlin; Strahler, Alan H.
    The radiative transfer equations for a coupled atmosphere and canopy are solved numerically by an improved Gause-Seidel iteration algorithm. The radiation field is decomposed into three components: unscattered sunlight, single scattering, and multiple scattering radiance for which the corresponding equations and boundary conditions are set up and their analytical or iterational solutions are explicitly derived. The classic Guass-Seidel algorithm has been widely applied in atomospheric research. This is its first application for calculating the multiple scattering radiance of a coupled atmosphere and canopy. This algorithm enables us to obtain the internal radiation field as well as radiances at boundaries. Any form of bidirectional reflectance distribution function (BRDF) as a boundary condition can be easily incorporated into the iteration procedure. The hotspot effect of the canopy is accommodated by means of the modification of the extiniction coefficients of upward single scattering radiation and unscatteered sunlight using the formulation of Nilson and Kuusk. To reduce the computation for the case of large optical thickness, an improved iteration formula is derived to speed convergence. The upwelling radiances have been evaluated for different atmospheric conditions, leaf area index (LAI), leaf angle distribution (LAD), leaf size and so on. The formulation presented in this paper is also well suited to analyze the relative magnitude of multiple scattering radiance and single scattering radiance in both the visible and near infrared regions.
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    An Analytic BRDF Model of Canopy Radiative Transfer and Its Inversion
    (Institute of Electrical and Electronics Engineers, 1993-09) Liang, Shunlin; Strahler, Alan H.
    Radiative transfer modeling of the bidirectional reflectance distribution function (BRDF) of leaf canopies is a powerful tool to relate multiangle remotely sensed data to biophysical parameters of the leaf canopy and to retrieve such parameters from multiangle imagery. However, the approximate approaches for multiple scattering that are used in the inversion of existing models are quite limited, and the sky radiance frequently is simply treated as isotropic. This paper presents an analytical model based on a rigorous canopy radiative transfer equation in which the multiple-scattering component is approximated by asymptotic theory and the single-scattering calculation, which requires numerical integration to properly accommodate the hotspot effect, is also simplified. Because the model is sensitive to angular variation in sky radiance, we further provide an accompanying new formulation for directional radiance in which the unscattered solar radiance and single-scattering radiance are calculated exactly, and multiple-scattering is approximated by the well-known two-stream Dirac delta function approach. A series of validations against exact calculations indicates that both models are quite accurate, especially when the viewing angle is smaller than 55 degrees. The Powell algorithm is then used to retrieve biophysical parameters from multiangle observations based on both the canopy and the sky radiance distribution models. The results using the soybean data of Ranson et al. to recover four of nine soybean biophysical parameters indicate that inversion of the present canopy model retrieves leaf area index well. Leaf angle distribution was not retrieved as accurately for the same dataset, perhaps because these measurements do not describe the hotspot well. Further experiments are required to explore the applicability of this canopy model.