Morphometric comparisons between automated and manual karst depression inventories in Apalachicola National Forest,Florida, and Mammoth Cave National Park,Kentucky, USA

Karst depression catalogs are critical to assessing the hydrology and geohazards of an area; yet, the delineation of these features within a landscape can be a difficult, time-consuming and subjective task. This study evaluates the efficacy of karst depression inventorying using an automated fill-difference method operating on high-resolution lidar-derived digital elevation models (DEMs). The resulting catalog is compared with existing karst depression inventories for two low-development areas of the USA, Mammoth Cave National Park (MACA) and Apalachicola National Forest (ANF), where karst depressions have been mapped previously using a manual closed-contour approach. The automated fill method captures 93 and 85 % of these previously mapped karst depressions at MACA and ANF, respectively. Field observations and topographic analysis suggest that the omitted features were likely misclassified within the existing catalogs. The automated routine returns 797 and 3377 additional topographic depressions, at MACA and ANF, respectively, which are not included in the existing catalogs. While the geology of ANF is mostly homogenous Quaternary deposits, the newly identified, typically smaller-scale depressions found within MACA tend to be disproportionally located in non-carbonate-dominated formations, where the development of karst may be restricted by geologic heterogeneity. Within both areas, the size distributions of the two inventories are statistically identical for features larger than ~10³ m² in area or ~3 m in depth. For individual depressions captured by both methods at MACA, the automated fill-difference routine tends to return a slightly larger estimate of depression size and aggregate small depressions into larger ones. Conversely, at ANF, some low-relief depressions may be disaggregated by the fill-difference technique, with a trend toward smaller estimated depression areas when the automated method is employed. The automated fill-difference method, operating on high-resolution lidar-derived DEMs, can reproduce and expand the existing inventories of karst depressions, while minimizing false detections that may be inherent within pre-existing catalogs.     

Flow localization in fissure eruptions

 During a basaltic fissure eruption heat transfer from the hot magma to the surrounding rock causes a dramatic increase in the magmatic viscosity and solidification at the margins. Both viscosity contrast and solidification can amplify initial variations in the flow rate and lead to localization of the flow along the strike of the fissure. However, for typical parameters, amplification driven by solidification is slower and significantly weaker than amplification driven by viscosity variations. In fact, for the parameters examined, the amplification due to solidification is so weak that its effect is almost insignificant, whereas viscosity variation provides a strong active mechanism for flow localization. Laboratory experiments illustrate viscous localization and suggest that this mechanism is robust. The dependence of viscosity on temperature can cause a small change in the pressure of the magma chamber to lead to a large jump in the flow rate of magma through the fissure. Received: 13 March 1998 / Accepted: 27 September 1998     

The queen conch fishery on Pedro Bank, Jamaica: discovery, development, management

The history, methods, problems and regulation of fishing of the last remaining large queen conch resource in the world, located on a Jamaican fishing bank, are examined. The fishery activities for the queen conch, Strombus gigas Linnaeus are briefly described with the main activities in the industrial sector which produce the bulk of the harvest, which is exported. There are a few large producers harvesting the single major fishing ground of Pedro Bank, southwest of Kingston. These fishers harvested at least 1500 t annually between 1992 and 1998. Management is by licensing, individual quotas and a close season from July to October. Regulations related to CITES are thought to greatly assist in making licensed harvesters provide catch data to the Fisheries Division. The industrial operators have provided funding to undertake stock assessment studies in 1994 and again in 1997. We highlight the focus on management on a participatory consensual approach with meetings with all players in the industry. The conch fishery is thought to be one of the few areas of the Jamaica fishery where there is close and successful collaboration between fishers and the Fisheries Division. It provides an example of how rapid, precautionary, participatory action can provide an adequate basis for management until more definitive scientific information becomes available. The status of the conch fishery is thought to be sustainable at present, once reductions are made to the annual quota.     

1951年以来奥地利人口变化的空间特征

根据1951-2001年奥地利人口调查统计数据,分析了近50年来奥地利人口变化的时空间规律,以及人口变化中的增长区和下降区的区域配置等特征,并建立人口变化模式。研究表明：20世纪后半叶奥地利经历了其他欧盟国所表现出的城市化、城市郊区化和人口老龄化的各个过程。特别是城市老龄化表现更为突出,据预测推算,到2035年奥地利将会有1/3的人口超过60岁。在分析过程中,不仅应用了行政区划的区域方法,而且也依据土地利用的经济性质,在“土地经济生产小区”的基底上,对人口的变化规律进行了更为深入的透视。研究结果显示：奥地利西部阿尔卑斯山地中的城市区域人口增长幅度最大。沿着捷克和斯洛伐克边界伸展的北部和东北部区域是最严重的人口缺失地区。而奥地利阿尔卑斯山地东部的一些早期产业都市及其郊区,乃至更远一些的南部和东南部的老工业区域,目前由于普遍存在着经济的困境,也直接导致了这些地区人口的下降。但奥地利未来的总人口趋势将持续稳定。     

Validation of official erosion modelling based on high‐resolution radar rain data by aerial photo erosion classification

The universal soil loss equation (USLE) is the most frequently applied erosion prediction model and it is also implemented as an official decision‐making instrument for agricultural regulations. The USLE itself has been already validated using different approaches. Additional errors, however, arise from input data and interpolation procedures that become necessary for field‐specific predictions on a national scale for administrative purposes. In this study, predicted event soil loss using the official prediction system in Bavaria (Germany) was validated by comparison with aerial photo erosion classifications of 8100 fields. Values for the USLE factors were mainly taken from the official Bavarian high‐resolution (5 × 5 m²) erosion cadastre. As series of erosion events were examined, the cover and management factor was replaced by the soil loss ratio. The event erosivity factor was calculated from high‐resolution (1 × 1 km², 5 min), rain gauge‐adjusted radar rain data (RADOLAN). Aerial photo erosion interpretation worked sufficiently well and average erosion predictions and visual classifications correlated closely. This was also true for data broken down to individual factors and different crops. There was no reason to assume a general invalidity of the USLE and the official parametrization procedures. Event predictions mainly suffered from errors in the assumed crop stage period and tillage practices, which do not reflect interannual and farm‐specific variation. In addition, the resolution of radar data (1 km²) did not seem to be sufficient to predict short‐term erosion on individual fields given the strong spatial gradients within individual rains. The quality of the input data clearly determined prediction quality. Differences between USLE predictions and observations are most likely caused by parametrization weaknesses but not by a failure of the model itself. Copyright © 2017 John Wiley & Sons, Ltd.     

Effects of a high rise building on wind flow and beach characteristics at Atlantic City, NJ, USA

This study assesses the effects of a high rise building on the beach and dune at an intensively developed shoreline through field investigation of geomorphological and sedimentological characteristics and wind tunnel investigation of wind speed and direction. Results indicate that wind speed is increased close to the building, where wind is often deflected to a more onshore direction. Obliquely offshore northwesterly winds are the most dramatically altered and cause onshore flows (with pronounced upward flows) in the landward portion of the beach near the building. Onshore deflections in wind direction cause besanding of the boardwalk and create highly localized scour and deposition zones. A dune on the backbeach breaks up zones of sediment transport and scour and diminishes the likelihood that scour areas will cause increased hazard to landward buildings as a result of flooding. Generic large-scale studies are required to develop criteria for communities to use to specify optimum dimensions, locations and shapes of landforms that are modified or created by high rise structures.     

The transient oasis: Nutrient-phytoplankton dynamics and particle export in Hawaiian lee cyclones

Macronutrients, photosynthetic pigments, and particle export were assessed in two eddies during the E-Flux I and III cruises to investigate linkages between biogeochemical properties and export flux in Hawaiian lee cyclonic eddies. Cyclone Noah (E-Flux I), speculated to be in the ‘decay’ stage, exhibited modest increases in macronutrients and photosynthetic pigments at the eddy center compared to ambient waters. Cyclone Opal (E-Flux III) also exhibited modest increases in macronutrient concentrations, but a 2-fold enhancement in total chlorophyll a (TChl a) concentration within the eddy center. As indicated by fucoxanthin concentrations, the phytoplankton community in the deep chlorophyll maximum (DCM) of Opal was comprised mainly of diatoms. During an 8-day time series in the center of Opal, TChl a concentration and fucoxanthin in the DCM decreased by 50%, which was potentially triggered by silicic acid limitation. Despite the presence of a substantial diatom bloom, Opal did not deliver the expected export of particulate carbon and nitrogen, but rather a large biogenic silica export (4-fold increase relative to export in surrounding waters). Results suggest that controls on the life cycle of a Hawaiian lee cyclone are likely a combination of physical (eddy dynamics), chemical (nutrient limitation), and biological (growth and grazing imbalance) processes. Comparisons between Noah and Opal and previously studied cyclones in the region point to a relationship between the spin-up duration of a cyclone and the resulting biological response. Nonetheless, Hawaiian lee cyclones, which strongly influence the biogeochemistry of areas 100's of km in scale in the subtropical North Pacific Ocean, still remain an enigma.