How hurricane attributes determine the extent of environmental effects: Multiple hurricanes and different coastal systems

The most recent spate of hurricanes to strike the United States and Caribbean (1989 to the present) has occurred when many of the affected areas had long-term water quality and biological data collection efforts ongoing, as well as special follow-up studies. These data have allowed researchers to obtain a much clearer picture of how individual characteristics of hurricanes interact with human land use to lead to various types and degrees of environmental effects. Common deleterious water quality effects associated with hurricanes include excessive nutrient loading, algal blooms, elevated biochemical oxygen demand and subsequent hypoxia and anoxia, fish and invertebrate kills, aquatic animal displacements, large scale releases of chemical pollutants and debris from damaged human structures, exacerbated spread of exotic species and pathogens, and pollution of water with fecal microbial pathogens. These and other effects may or may not occur, or occur to varying degrees, depending upon individual hurricane characteristics including category, point of landfall, wind speed, amount of rainfall, and path after landfall. Landfall in a populous area, a post-landfall trajectory upriver toward a headwater region, passage along a floodplain containing pollution sources (such as wastewater treatment plants, concentrated animal feeding operations, and septic systems), and intensity sufficient to damage power generation will all lead to increased environmental damage. We suggest a number of recommendations for post-hurricane water sampling parameters and techniques, and provide several management-oriented recommendations for better coastal and floodplain land use aimed at lessening the water quality effects of hurricanes.     

Transnational ruptures and sutures: questions of identity and social relations among Guatemalans in Canada

This article examines the ruptures and sutures of Guatemalan refugee transnationalism in the context of settlement in southern Ontario, Canada in the 1980s and 1990s. Political violence became deeply imbedded in `community' relations and subsequently ruptured the social fabric of Guatemala. Through the optic of transnationalism, this research examines the ways in which Guatemalans in Canada work to transform, rely on, and create new primary social relations that stretch across borders when face-to-face `community' connections are no longer possible. Transnational ruptures rather than transnational flows are evident due to varying legal status, the continuing instability, impunity, and insecurity associated with living conditions in Guatemala. Ruptures are reinforced by low income levels (in both countries) leading to lack of communication, and the physical distance between the two countries that inhibits regular travel. This revised version was published online in August 2006 with corrections to the Cover Date.     

Characterizing agricultural drought in the Karamoja subregion of Uganda with meteorological and satellite-based indices

Karamoja is notoriously food insecure and has been in need of food aid for most years during the last two decades. One of the main factors causing food insecurity is drought. Reliable, area-wide, long-term data for detecting and monitoring drought conditions are critical for timely, life-saving interventions and the long-term development of the region, yet such data are sparse or unavailable. Due to advances in satellite remote sensing, characterizing drought in data-sparse regions like Karamoja has become possible. This study characterizes agricultural drought in Karamoja to enable a comprehensive understanding of drought, concomitantly evaluating the suitability of NDVI-based drought monitoring. We found that in comparison with the existing data, NDVI data currently provide the best, consistent, and spatially explicit information for operational drought monitoring in Karamoja. Results indicate that the most extreme agricultural drought in recent years occurred in 2009 followed by 2004 and 2002 and suggest that in Karamoja, moderate to severe droughts (e.g., 2008) often have the same impact on crops and human needs (e.g., food aid) as extreme droughts (e.g., 2009). We present in a proof-of-concept frame, a method to estimate the number of people needing food assistance and the population likely to fall under the integrated food security phase classification (IPC) Phase 3 (crisis) due to drought severity. Our model indicates that 90.7% of the variation in the number of people needing aid can be explained by NDVI data and NDVI data can augment these estimates. We conclude that the biggest drivers of food insecurity are the cultivation of crops on marginal land with insignificant inputs, the lack of irrigation and previous systematic incapacitation of livestock (pastoral) alternatives through government programming. Further research is needed to bridge empirical results with social–economic studies on drought impacts on communities in the region to better understand additional factors that will need to be addressed to ensure livelihood resilience.     

Pb–Nd isotopic constraints on sedimentary input into the Lesser Antilles arc system

The Lesser Antilles arc is a particularly interesting island arc because it is presently very active, it is located perpendicular to the South American continent and its chemical and isotopic compositions display a strong north–south gradient. While the presence in the south of a thick pile of sedimentary material coming from the old South American continent has long been suspected to explain the geochemical gradient, previous studies failed to demonstrate unambiguously a direct link between the arc lava compositions and the subducted sediment compositions.Here, we present new Nd, Sm, Th, U and Pb concentrations and Nd–Pb isotopic data for over 60 sediments from three sites located in the fore arc region of the Lesser Antilles arc. New data for DSDP Site 543 drill core located east of Dominica Island complement the data published by White et al. [White, W.M., Dupré, B. and Vidal, P., 1985. Isotope and trace element geochemistry of sediments from the Barbados Ridge–Demerara Plain region, Atlantic Ocean. Geochimica et Cosmochimica Acta, 49: 1875–1886.] and confirm their relatively uniform isotopic compositions (i.e., ²⁰⁶Pb/²⁰⁴Pb between 19.13 and 19.53). In contrast, data obtained on DSDP Site 144 located further south, on the edge of the South American Rise and on sediments from Barbados Island are much more variable (²⁰⁶Pb/²⁰⁴Pb ranges from 18.81 to 27.69). The very radiogenic Pb isotopic compositions are found in a 60 m thick black shale unit, which has no age equivalent in the Site 543 drill core. We interpret the peculiar composition of the southern sediments as being due to two factors, (a) the proximity of the South American craton, which contributes coarse grain old detrital material that does not travel far from the continental shelf, and (b) the presence of older sediments including the thick black shale unit formed during Oceanic Anoxic events 2 and 3.The north–south isotopic change known along the Lesser Antilles arc can be explained by the observed geographical changes in the composition of the subducted sediments. About 1% contamination of the mantle wedge by Site 543 sediments explains the composition of the northern islands while up to 10% sediments like those of Site 144 is required in the source of the southern island lavas. The presence of black shales in the subducted pile provides a satisfactory explanation for the very low Δ8/4 values that characterize the Lesser Antilles arc.     

Large‐scale erosion and overbank deposition caused by the July 2013 flood of the Abu River,Yamaguchi City,Japan

This paper reports on the erosion, transport, and deposition processes associated with an overbank deposit formed by the flooding of the Abu River on July 28, 2013, in Yamaguchi City, Japan. At the study site, river flows overtopped the levee revetment upstream of a meander bend cutting it off and flowing back into the main channel downstream. In this sequential process, it deposited large amounts of sediments, ranging from mud to cobbles, on the floodplain. The surface of paddy fields adjacent to a railway line, located at the center of the affected floodplain, was severely eroded by the flood flows. Overbank deposits composed of both upstream finer sediments and eroded coarser terrestrial sediments are laid down in the affected area. Large amounts of pebbles and cobbles originating from the eroded terrestrial area formed a gravelly pile on top of the sand and gravel sediments derived from the river. This finding indicates that sands and gravels were deposited prior to the formation of the gravelly pile, probably before and during peak flood flows. An inverse grading structure is evident in the lower to middle part of these comparatively thick deposits, most likely due to differences in transport pattern between entrained terrestrial gravels and upstream finer sediments.     

Multi‐generational carbonate assemblages in martian meteorite Allan Hills 84001: Implications for nucleation,growth, and alteration

Abstract— The carbonate mineralogy of several complex carbonate‐rich regions in Allan Hills (ALH) 84001 has been examined. These regions contain familiar forms of carbonate, as well as textural forms previously unreported including carbonate rosettes, planiform “slab” carbonates, distinct “post‐slab” magnesites, and carbonates interstitial to feldspathic glass and orthopyroxene. Slab carbonates reveal portions of the carbonate growth sequence not seen in the rosettes and suggest that initial nucleating compositions were calcite‐rich. The kinetically controlled growth of rosettes and slab carbonates was followed by an alteration event that formed the magnesite‐siderite layers on the exterior surfaces of the carbonate. Post‐slab magnesite, intimately associated with silica glass, is compositionally similar to the magnesite in these exterior layers but represents a later generation of carbonate growth. Feldspathic glasses had little or no thermal effect on carbonates, as indicated by the lack of thermal decomposition or any compositional changes associated with glass/carbonate contacts.     

Toward a High-Resolution Monitoring of Continental Surface Water Extent and Dynamics,at Global Scale: from GIEMS (Global Inundation Extent from Multi-Satellites) to SWOT (Surface Water Ocean Topography)

Up to now, high-resolution mapping of surface water extent from satellites has only been available for a few regions, over limited time periods. The extension of the temporal and spatial coverage was difficult, due to the limitation of the remote sensing technique [e.g., the interaction of the radiation with vegetation or cloud for visible observations or the temporal sampling with the synthetic aperture radar (SAR)]. The advantages and the limitations of the various satellite techniques are reviewed. The need to have a global and consistent estimate of the water surfaces over long time periods triggered the development of a multi-satellite methodology to obtain consistent surface water all over the globe, regardless of the environments. The Global Inundation Extent from Multi-satellites (GIEMS) combines the complementary strengths of satellite observations from the visible to the microwave, to produce a low-resolution monthly dataset (\(0.25^\circ \,\times \,0.25^\circ\)) of surface water extent and dynamics. Downscaling algorithms are now developed and applied to GIEMS, using high-spatial-resolution information from visible, near-infrared, and synthetic aperture radar (SAR) satellite images, or from digital elevation models. Preliminary products are available down to 500-m spatial resolution. This work bridges the gaps and prepares for the future NASA/CNES Surface Water Ocean Topography (SWOT) mission to be launched in 2020. SWOT will delineate surface water extent estimates and their water storage with an unprecedented spatial resolution and accuracy, thanks to a SAR in an interferometry mode. When available, the SWOT data will be adopted to downscale GIEMS, to produce a long time series of water surfaces at global scale, consistent with the SWOT observations.