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51.
John W. Day Robert R. Christian Donald M. Boesch Alejandro Yáñez-Arancibia James Morris Robert R. Twilley Larissa Naylor Linda Schaffner Court Stevenson 《Estuaries and Coasts》2008,31(3):477-491
Climate impacts on coastal and estuarine systems take many forms and are dependent on the local conditions, including those
set by humans. We use a biocomplexity framework to provide a perspective of the consequences of climate change for coastal
wetland ecogeomorphology. We concentrate on three dimensions of climate change affects on ecogeomorphology: sea level rise,
changes in storm frequency and intensity, and changes in freshwater, sediment, and nutrient inputs. While sea level rise,
storms, sedimentation, and changing freshwater input can directly impact coastal and estuarine wetlands, biological processes
can modify these physical impacts. Geomorphological changes to coastal and estuarine ecosystems can induce complex outcomes
for the biota that are not themselves intuitively obvious because they are mediated by networks of biological interactions.
Human impacts on wetlands occur at all scales. At the global scale, humans are altering climate at rapid rates compared to
the historical and recent geological record. Climate change can disrupt ecological systems if it occurs at characteristic
time scales shorter than ecological system response and causes alterations in ecological function that foster changes in structure
or alter functional interactions. Many coastal wetlands can adjust to predicted climate change, but human impacts, in combination
with climate change, will significantly affect coastal wetland ecosystems. Management for climate change must strike a balance
between that which allows pulsing of materials and energy to the ecosystems and promotes ecosystem goods and services, while
protecting human structures and activities. Science-based management depends on a multi-scale understanding of these biocomplex
wetland systems. Causation is often associated with multiple factors, considerable variability, feedbacks, and interferences.
The impacts of climate change can be detected through monitoring and assessment of historical or geological records. Attribution
can be inferred through these in conjunction with experimentation and modeling. A significant challenge to allow wise management
of coastal wetlands is to develop observing systems that act at appropriate scales to detect global climate change and its
effects in the context of the various local and smaller scale effects. 相似文献
52.
Post-fire debris flows represent one of the most erosive consequences associated with increasing wildfire severity and investigations into their downstream impacts have been limited. Recent advances have linked existing hydrogeomorphic models to predict potential impacts of post-fire erosion at watershed scales on downstream water resources. Here we address two key limitations in current models: (1) accurate predictions of post-fire debris flow volumes in the absence of triggering storm rainfall intensities and (2) understanding controls on grain sizes produced by post-fire debris flows. We compiled and analysed a novel dataset of depositional volumes and grain size distributions (GSDs) for 59 post-fire debris flows across the Intermountain West (IMW) collected via fieldwork and from the literature. We first evaluated the utility of existing models for post-fire debris flow volume prediction, which were largely developed for Southern California. We then constructed a new post-fire debris flow volume prediction model for the IMW using a combination of Random Forest modelling and regression analysis. We found topography and burn severity to be important variables, and that the percentage of pre-fire soil organic matter was an essential predictor variable. Our model was also capable of predicting debris flow volumes without data for the triggering storm, suggesting that rainfall may be more important as a presence/absence predictor, rather than a scaling variable. We also constructed the first models that predict the median, 16th percentile, and 84th percentile grain sizes, as well as boulder size, produced by post-fire debris flows. These models demonstrate consistent landscape controls on debris flow GSDs that are related to land cover, physical and chemical weathering, and hillslope sediment transport processes. This work advances our ability to predict how post-fire sediment pulses are transported through watersheds. Our models allow for improved pre- and post-fire risk assessments across diverse ranges of watersheds in the IMW. 相似文献
53.
Danielle H. Buchanan Larissa A. Naylor Martin D. Hurst Wayne J. Stephenson 《地球表面变化过程与地形》2020,45(4):1028-1037
The majority of shore platforms form in rocks that are characterised by layered stratigraphy and pervasive jointing. Plucking of weathered, joint and bed bounded blocks is an important erosion process that existing models of platform development do not represent. Globally, measuring platform erosion rates have focused on microscale (< 1 mm) surface lowering rather than mesoscale (0.1-1 m) block detachment, yet the latter appears to dominate the morphological development of discontinuity rich platforms. Given the sporadic nature of block detachment on platforms, observations of erosion from storm event to multi-decadal timescales (and beyond) are required to quantify shore platform erosion rates. To this end, we collected aerial photography using an unmanned aerial vehicle to produce structure-from-motion-derived digital elevation models and orthophotos. These were combined with historical aerial photographs to characterise and quantify the erosion of two actively eroding stratigraphic layers on a shore platform in Glamorgan, south Wales, UK, over 78-years. We find that volumetric erosion rates vary over two orders of magnitude (0.1-10 m3 yr-1) and do not scale with the length of the record. Average rates over the full 78-year record are 2-5 m3 yr-1. These rates are equivalent to 1.2-5.3 mm yr-1 surface lowering rates, an order of magnitude faster than previously published, both at our site and around the world in similar rock types. We show that meso-scale platform erosion via block detachment processes is a dominant erosion process on shore platforms across seasonal to multi-decadal timescales that have been hitherto under-investigated. © 2019 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd 相似文献