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English E.,Stratus Consulting Inc.
American Journal of Agricultural Economics | Year: 2010

Models of recreation behavior have typically ignored the role of fixed annual fees, such as the fee for a recreational license, in determining choice and welfare. We demonstrate how techniques from the literature on discrete-continuous choice and two-part tariffs can address a situation where fixed annual fees are essential to determining the choice of a recreation site. We explore how accounting for value captured by fixed fees can influence the way resource changes are assessed. © The Author (2010). Published by Oxford University Press on behalf of the Agricultural and Applied Economics Association. All rights reserved. Source

Wobus C.W.,Stratus Consulting Inc. | Wobus C.W.,University of Colorado at Boulder | Tucker G.E.,University of Colorado at Boulder | Anderson R.S.,University of Colorado at Boulder
Journal of Geophysical Research: Earth Surface | Year: 2010

Incised fluvial systems are typically interpreted as recording geologically recent changes in either climate or tectonics. However, few diagnostic tools exist to evaluate whether particular incised landscapes primarily reflect climatic or tectonic perturbation. Here we summarize the results of a simple fluvial sediment transport model that allows us to contrast patterns of fluvial incision driven by changes in hydrology and sediment flux ("climate") with those driven by changes in rock uplift patterns relative to sea level ("tectonics"). Our modeling suggests that there may be diagnostic differences between the spatial and temporal patterns of incision caused by these different processes. In particular, incision driven by climate change is most commonly accompanied by downstream migrating waves of incision and decreases in channel gradient, while under most circumstances incision driven by tectonics will be accompanied by upstream migrating incision and increases in channel gradient. We apply our modeling to a case study of the North American High Plains, where regionally elevated surfaces east of the Rockies have been incised up to 500 m by the fluvial systems draining the core of the range. Although this incision has been interpreted as reflecting a tectonic rejuvenation of the High Plains, our analysis suggests that climate change is at least as plausible an explanation to explain the incision of this landscape. Diagnostic differences between the climate and tectonic end-member scenarios might be obtained via detailed study of the spatial and temporal patterns of terrace abandonment, providing a potentially fruitful target for field investigation. Copyright 2010 by the American Geophysical Union. Source

Overeem I.,University of Colorado at Boulder | Anderson R.S.,University of Colorado at Boulder | Wobus C.W.,Stratus Consulting Inc. | Wobus C.W.,University of Colorado at Boulder | And 3 more authors.
Geophysical Research Letters | Year: 2011

Erosion rates of permafrost coasts along the Beaufort Sea accelerated over the past 50 years synchronously with Arctic-wide declines in sea ice extent, suggesting a causal relationship between the two. A fetch-limited wave model driven by sea ice position and local wind data from northern Alaska indicates that the exposure of permafrost bluffs to seawater increased by a factor of 2.5 during 1979-2009. The duration of the open water season expanded from ∼45 days to ∼95 days. Open water expanded more rapidly toward the fall (∼0.92 day yr -1), when sea surface temperatures are cooler, than into the mid-summer (∼0.71 days yr -1).Time-lapse imagery demonstrates the relatively efficient erosive action of a single storm in August. Sea surface temperatures have already decreased significantly by fall, reducing the potential impact of thermal erosion due to fall season storm waves. Copyright 2011 by the American Geophysical Union. Source

Barnhart K.R.,University of Colorado at Boulder | Anderson R.S.,University of Colorado at Boulder | Overeem I.,University of Colorado at Boulder | Wobus C.,Stratus Consulting Inc. | And 2 more authors.
Journal of Geophysical Research: Earth Surface | Year: 2014

The Arctic climate is changing, inducing accelerating retreat of ice-rich permafrost coastal bluffs. Along Alaska's Beaufort Sea coast, erosion rates have increased roughly threefold from 6.8 to 19 m yr-1 since 1955 while the sea ice-free season has increased roughly twofold from 45 to 100 days since 1979. We develop a numerical model of bluff retreat to assess the relative roles of the length of sea ice-free season, sea level, water temperature, nearshore wavefield, and permafrost temperature in controlling erosion rates in this setting. The model captures the processes of erosion observed in short-term monitoring experiments along the Beaufort Sea coast, including evolution of melt notches, topple of ice wedge-bounded blocks, and degradation of these blocks. Model results agree with time-lapse imagery of bluff evolution and time series of ocean-based instrumentation. Erosion is highly episodic with 40% of erosion is accomplished during less than 5% of the sea ice-free season. Among the formulations of the submarine erosion rate we assessed, we advocate those that employ both water temperature and nearshore wavefield. As high water levels are a prerequisite for erosion, any future changes that increase the frequency with which water levels exceed the base of the bluffs will increase rates of coastal erosion. The certain increases in sea level and potential changes in storminess will both contribute to this effect. As water temperature also influences erosion rates, any further expansion of the sea ice-free season into the midsummer period of greatest insolation is likely to result in an additional increase in coastal retreat rates. Key Points Coastal erosion is episodic and associated with storms that set up water Heat transfer governs the rate of submarine notch incision and coast retreat Sea level and water temperature will impact future coastal erosion the most ©2014. American Geophysical Union. All Rights Reserved. Source

Uejio C.K.,University of Wisconsin - Madison | Wilhelmi O.V.,U.S. National Center for Atmospheric Research | Golden J.S.,Duke University | Mills D.M.,Stratus Consulting Inc. | Gulino S.P.,Philadelphia University
Health and Place | Year: 2011

Extreme heat is an important weather hazard associated with excess mortality and morbidity. We determine the relative importance of heat exposure and the built environment, socioeconomic vulnerability, and neighborhood stability for heat mortality (Philadelphia, PA, USA) or heat distress (Phoenix, AZ, USA), using an ecologic study design. We use spatial Generalized Linear and Mixed Models to account for non-independence (spatial autocorrelation) between neighboring census block groups. Failing to account for spatial autocorrelation can provide misleading statistical results. Phoenix neighborhoods with more heat exposure, Black, Hispanic, linguistically and socially isolated residents, and vacant households made more heat distress calls. Philadelphia heat mortality neighborhoods were more likely to have low housing values and a higher proportion of Black residents. Our methodology can identify important risk factors and geographic areas to target interventions. © 2010 Elsevier Ltd. Source

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