Evaluating the effects of urbanization age on the morphology of low-order urban streams in the U.S. southern Piedmont

We used space-for-time substitution, correlation, and regression analyses to study the effects of urbanization age on stream channel variables from 19 low-order urban watersheds in the southern Piedmont of the United States. The results are used to address questions regarding which variables are most responsive to urbanization age, the duration of response relative to system size, and changes in adjustment rate over time. Few morphological variables were found to be well correlated with metrics of urbanization age. The maximum-width/maximum-depth ratio (Wmax/Dmax) exhibited the best correlations to multiple metrics of urbanization age, with all correlations positive. A dearth of young urbanization ages in our dataset makes mathematically derived response times and end states for Wmax/Dmax highly uncertain. Inferences from the age range that is better represented suggest that the period of major response has occurred within the first three decades following urbanization. Subsequently, gradual increase in Wmax/Dmax appears to continue over 40 or more years. Response of channel form to urbanization and time elapsed in these low-order Piedmont streams is constrained by the presence of resistant bedrock below streambeds, a circumstance addressed by recent channel evolution models.     

基于地震与非地震联合约束下复杂冲断带构造建模:以西昆仑山前柯东构造带为例

柯东构造带是揭示西昆仑山前冲断带变形过程的关键区之一,也是当前油气勘探重要的目标区。由于该区构造变形 强、地层速度变化快以及地表条件复杂等因素,导致当前勘探面临着地震勘探资料品质差,构造建模多解性强等问题。文 章利用R型因子降维分析方法,通过对柯东构造带甫沙地区的重、磁、电反演成果进行降维分析,结果表明甫沙地区深部 发育断块构造,不存在地震剖面上显示的背斜构造;同时联合地震资料的综合解释,认为现今的甫沙地区发育的断块构造 是早期的完整背斜受早更新世山前右旋走滑断裂改造的结果。在柯东构造带的综合建模实践表明,通过地震与非地震方法 的联合约束可以为认识复杂冲断带的构造变形提供有效的手段。     

THE DRIVING FORCES OF LAND CHANGE IN THE NORTHERN PIEDMONT OF THE UNITED STATES

Driving forces facilitate or inhibit land‐use / land‐cover change. Human driving forces include political, economic, cultural, and social attributes that often change across time and space. Remotely sensed imagery provides regional land‐change data for the Northern Piedmont, an ecoregion of the United States that continued to urbanize after 1970 through conversion of agricultural and forest land covers to developed uses. Eight major driving forces facilitated most of the land conversion; other drivers inhibited or slowed change. A synergistic web of drivers may be more important in understanding land change than individual drivers by themselves.     

Sedimentation model of gravel-dominated alluvial piedmont fan,Ganga Plain,India

The Piedmont Zone of the Indo-Gangetic Plain contains numerous, laterally coalescing small alluvial fans. The Latest Pleistocene–Holocene 30 km long Gaula Fan can be divided into gravelly proximal fan (0–14 km down-stream), gravel-sand rich mid fan (14–22 km) and sand–mud dominated distal fan (22–30 km). The fan succession is composed of two fan expansion cycles A and B. Separated by an undulatory erosional contact of regional extent, cycle A is characterized by river borne clast-supported gravelly deposits, and the overlying fan expansion cycle B by matrix-supported gravely debris flows. The main process behind fan development has been lateral migration of channels over the fan surface probably due to rapid sedimentation caused by increased sediment supply, and the fluctuating water budget in response to changing climate. The water laid expansion cycle A represents a humid phase. The debris flow deposits of expansion cycle B suggest a dry phase. Approximately between 8 and 3 Ka, cycle B also indicates a phase of tectonic instability in the Siwalik Hills forming the mountain front. The tectonic activity caused incision of rivers into the fan surface, and in turn resulted in reduced fan-building activity. At present the fan surface is accreting by sheet flow processes.     

Reconstructing a cultural fire regime in the Pennsylvania Anthracite Region

Abstract

Fire history reconstructions provide fire managers with valuable information regarding historical fire regime dynamics. Yet, in the Central Hardwood Forest Region (CHF), there is an absence of dendroecological studies where frequent wildfires have persisted into the twenty-first century. This study presents the first documented tree-ring reconstruction of fire history in the Pennsylvania anthracite coal-producing region. An approximately 150-year fire chronology was developed from fire-scarred pitch pine (Pinus rigida) and sassafras (Sassafras albidum) collected on Spring Mountain in Schuylkill County. Principal component analysis and k-means cluster analysis were used to identify four fire regime clusters based on interacting fire and non-fire parameters. Results indicate that fires occurred under a variety of moisture conditions and that a mid-twentieth century increase in fire activity on Spring Mountain was associated with the collapse of the regional anthracite industry and possibly amplified by the 1960s drought. Fires continue to burn on Spring Mountain in the twenty-first century, contrary to the dominant pattern of fire exclusion across the CHF. Future research needs are highlighted regarding historical fire regime dynamics and cultural ties to landscape burning in the Pennsylvania Anthracite Region.     

Variation in low food access areas due to data source inaccuracies

Several spatial measures of community food access identifying so called “food deserts” have been developed based on geospatial information and commercially-available, secondary data listings of food retail outlets. It is not known how data inaccuracies influence the designation of Census tracts as areas of low access. This study replicated the U.S. Department of Agriculture Economic Research Service (USDA ERS) food desert measure and the Centers for Disease Control and Prevention (CDC) non-healthier food retail tract measure in two secondary data sources (InfoUSA and Dun & Bradstreet) and reference data from an eight-county field census covering 169 Census tracts in South Carolina. For the USDA ERS food deserts measure accuracy statistics for secondary data sources were 94% concordance, 50–65% sensitivity, and 60–64% positive predictive value (PPV). Based on the CDC non-healthier food retail tracts both secondary data demonstrated 88–91% concordance, 80–86% sensitivity and 78–82% PPV. While inaccuracies in secondary data sources used to identify low food access areas may be acceptable for large-scale surveillance, verification with field work is advisable for local community efforts aimed at identifying and improving food access.     

天山北坡中段主要河流的枯季径流分析

枯水径流是构成河川径流年内分配的重要组成部分,在水资源评价、生态环境及工程水文分析计算中是必不可少的,它是河川径流的一种特殊形态。研究区域地处新疆经济社会发展的中心地带—天山北坡经济带,是水资源紧缺地区,对其枯季径流进行较深入的分析研究,有其重要的现实意义。对天山北坡中段主要河流的冬季、枯水期、最小月和最小日平均流量作了初步分析,并提出某些区域性的基本规律。     

长岭山北麓断裂晚第四纪活动性及构造稳定性研究

通过野外调查表明,长岭山北麓断裂晚第四纪以来表现出强烈的新活动性.沿断裂年青冲沟以及最新阶地发生水平左旋位移,通过测量及位移量的分组分析并结合相关年代计算得到,该活动断裂晚更新世以来水平滑动速率为5.1mm/a,垂直滑动速率为0.19mm/a;全新世以来水平滑动速率3.53±0.34 mm/a,垂直滑动速率0.29±0.03 mm/a.沿断裂全线进行分析并结合断层剖面得到,小红山一带断层上覆0.4～1.2 m的坡洪积层(底部TL年龄6.1±0.7 kaBP)未被错动,而且Ⅰ级河流阶地及河漫滩相沉积物均未发生变形变位.1927年古浪8.0级地震形成的地表破裂向东抵达下井子沟地区,但未通过陶家山北的明代长城.区域分析表明,长岭山北麓断层构成古浪活动断裂带的东延段,和前人已经确定的天桥沟断层、黄羊川断层一起构成古浪左旋走滑兼逆冲活动断裂带.1927年古浪8.0级地震形成大破裂--贯通型的地震地表破裂带,说明该断裂所在地区为破裂的成熟地段.通过计算,并考虑到古浪大地震的离逝时间以及结合区域资料分析表明,该活动断裂所在地区至少500a内是相对稳定的,1000a的预测时段内发生强、大地震的概率也很低,但是不排除发生中强地震的可能.     

太行山山前断裂带中北段晚第四纪活动性研究

The location and late Quaternary activity of the Central-North Segment of the Taihang Mountains Piedmont fault zone have been studied by shallow seismic survey and combined drill exploration.Our results show that the Baoding-Shijiazhuang fault and the Xushui fault were active in the late Pleistocene,but the south Xushui fault has been inactive since the late Pleistocene.The maximum magnitude of potential earthquake of the faults is 6.0.     

痕量氢气连续观测仪稳定性分析

断裂带氢气浓度连续观测是获取深部构造活动的重要气体地球化学指标之一。由于断裂带岩层氢气浓度背景值较低,因此检验和分析氢气观测仪器的绝对检出限以及仪器稳定性便是选择高效能氢气浓度观测仪器的重要环节。在中条山山前断裂的夏县东郭测点开展了同一取样点相同环境的2套痕量氢气观测仪器对比实验,从记录的资料分析,两条曲线变化趋势、变化形态基本一致,但在细节上稍有差别,通过拟合分析,使用相关系数进行校正后,两条曲线基本重合。结果表明,痕量氢气自动分析仪稳定好,灵敏度高,观测结果一致,且实现了数字化,能够满足地震活动监测工作的需求。