Thresholds for post-wildfire debris flows: Insights from the Pinal Fire,Arizona, USA     

Carissa A. Raymond  Luke A. McGuire  Ann M. Youberg  Dennis M. Staley  Jason W. Kean 《地球表面变化过程与地形》2020,45(6):1349-1360

Wildfire significantly alters the hydrologic properties of a burned area, leading to increases in overland flow, erosion, and the potential for runoff-generated debris flows. The initiation of debris flows in recently burned areas is well characterized by rainfall intensity-duration (ID) thresholds. However, there is currently a paucity of data quantifying the rainfall intensities required to trigger post-wildfire debris flows, which limits our understanding of how and why rainfall ID thresholds vary in different climatic and geologic settings. In this study, we monitored debris-flow activity following the Pinal Fire in central Arizona, which differs from both a climatic and hydrogeomorphic perspective from other regions in the western United States where ID thresholds for post-wildfire debris flows are well established, namely the Transverse Ranges of southern California. Since the peak rainfall intensity within a rainstorm may exceed the rainfall intensity required to trigger a debris flow, the development of robust rainfall ID thresholds requires knowledge of the timing of debris flows within rainstorms. Existing post-wildfire debris-flow studies in Arizona only constrain the peak rainfall intensity within debris-flow-producing storms, which may far exceed the intensity that actually triggered the observed debris flow. In this study, we used pressure transducers within five burned drainage basins to constrain the timing of debris flows within rainstorms. Rainfall ID thresholds derived here from triggering rainfall intensities are, on average, 22 mm h⁻¹ lower than ID thresholds derived under the assumption that the triggering intensity is equal to the maximum rainfall intensity recorded during a rainstorm. We then use a hydrologic model to demonstrate that the magnitude of the 15-min rainfall ID threshold at the Pinal Fire site is associated with the rainfall intensity required to exceed a recently proposed dimensionless discharge threshold for debris-flow initiation. Model results further suggest that previously observed differences in regional ID thresholds between Arizona and the San Gabriel Mountains of southern California may be attributed, in large part, to differences in the hydraulic properties of burned soils. © 2019 John Wiley & Sons, Ltd.  相似文献   

Investigation of the elevation of saltwater wedge due to subsurface dams     

Qinpeng Chang  Tianyuan Zheng  Youyuan Chen  Xilai Zheng  Marc Walther 《水文研究》2020,34(22):4251-4261

Subsurface dams are rather effective and used for the prevention of saltwater intrusion in coastal regions around the world. We carried out the laboratory experiments to investigate the elevation of saltwater wedge after the construction of subsurface dams. The elevation of saltwater wedge refers to the upward movement of the downstream saltwater wedge because the subsurface dams obstruct the regional groundwater flow and reduce the freshwater discharge. Consequently, the saltwater wedge cannot further extend in the longitudinal direction but rises in the vertical profile resulting in significant downstream aquifer salinization. In order to quantitatively address this issue, field-scale numerical simulations were conducted to explore the influence of various dam heights, distances, and hydraulic gradients on the elevation of saltwater wedge. Our investigation shows that the upward movement of the saltwater wedge and its areal extension in the vertical domain of the downstream aquifer become more severe with a higher dam and performed a great dependence on the freshwater discharge. Furthermore, the increase of the hydraulic gradient and the dam distance from the sea boundary leads to a more pronounced wedge elevation. This phenomenon comes from the variation of the freshwater discharge due to the modification of dam height, location, and hydraulic gradient. Large freshwater discharge can generate greater repulsive force to restrain the elevation of saltwater wedge. These conclusions provide theoretical references for the behaviour of the freshwater–seawater interface after the construction of subsurface dams and help optimize the design strategy to better utilize the coastal groundwater resources.  相似文献   

多点液压式波浪能海水淡化系统建模与仿真   总被引：1，自引：1，他引：0  

胡缘  杨绍辉  何宏舟  陈沪  郑松根  张迪 《海洋工程》2019,37(1):134-141

为缓解淡水资源短缺及化石能源过度使用问题,提出多点液压式波浪能海水淡化系统,该系统主要由采能装置、液压传递系统与反渗透膜海水淡化设备组成。系统的采能装置采用振荡浮子式,可将波浪能转换为浮子振荡从而被液压系统吸收达到采集波浪能的目的。为了提高液压式波浪能海水淡化系统的采能效率及淡水率,利用AMEsim软件对液压传递系统进行建模与仿真,分析了蓄能器、浮子个数及波高对液压传递系统输出响应的影响。结果表明:蓄能器能够使液压马达的输出响应更加稳定;当浮子的数量增加时,液压系统达到稳定的运行状态所需的时间更短,从而有利于提高系统的效率;波高在2 m左右时,本系统的产水量达到最大。  相似文献   

CMD180T型钻机在尚义地热井施工中的应用          下载免费PDF全文

王雷浩  李光宏  石逊  殷邈 《探矿工程》2020,47(1):58-61

经物探分析在河北省张家口尚义县大青沟镇南海子村东南1.0 km存在深部断裂构造，为了寻找开发坝上地区地热资源，决定在该位置施工一口2000 m深地热井，即穿过该断裂构造寻找导水通道，完成地热井施工任务。施工中采用了CMD180T型钻机，该钻机采用了先进的全液压传动系统，自动化程度高，性能优异，可大大降低操作人员的劳动强度且易于搬迁、易于操作。其优势在这次地热井工程施工过程中得到了充分的体现。  相似文献   

Subsurface flow measurements using passive flux meters in variably-saturated cold-regions landscapes     

Élise G. Devoie  Ryan F. Connon  James R. Craig  William L. Quinton 《水文研究》2020,34(23):4541-4546

To date, passive flux meters have predominantly been applied in temperate environments for tracking the movement of contaminants in groundwater. This study applies these instruments to reduce uncertainty in (typically instantaneous) flux measurements made in a low-gradient, wetland dominated, discontinuous permafrost environment. This method supports improved estimation of unsaturated and over-winter subsurface flows which are very difficult to quantify using hydraulic gradient-based approaches. Improved subsurface flow estimates can play a key role in understanding the water budget of this landscape.  相似文献   

Geostatistical features of streambed vertical hydraulic conductivities in Frenchman Creek Watershed in Western Nebraska     

Olufemi P. Abimbola  Aaron R. Mittelstet  Troy E. Gilmore 《水文研究》2020,34(16):3481-3491

This study evaluated the spatial variability of streambed vertical hydraulic conductivity (K_v) in different stream morphologies in the Frenchman Creek Watershed, Western Nebraska, using different variogram models. Streambed K_v values were determined in situ using permeameter tests at 10 sites in Frenchman, Stinking Water and Spring Creeks during the dry season at baseflow conditions. Measurements were taken both in straight and meandering stream channels during a 5 day period at similar flow conditions. Each test site comprised of at least three transects and each transect comprised of at least three K_v measurements. Linear, Gaussian, exponential and spherical variogram models were used with Kriging gridding method for the 10 sites. As a goodness-of-fit statistic for the variogram models, cross-validation results showed differences in the median absolute deviation and the standard deviation of the cross-validation residuals. Results show that using the geometric means of the 10 sites for gridding performs better than using either all the K_v values from the 93 permeameter tests or 10 K_v values from the middle transects and centre permeameters. Incorporating both the spatial variability and the uncertainty involved in the measurement at a reach segment can yield more accurate grid results that can be useful in calibrating K_v at watershed or sub-watershed scales in distributed hydrological models.  相似文献   

可替换式桥梁横向防落梁限位装置抗震性能研究          下载免费PDF全文

闫磊  安康  岳克锋  李果  尹修城  姜渝  付亚男 《世界地震工程》2020,(3):172-180

针对目前桥梁结构横向防落梁限位装置损毁后修复困难的问题，提出一种新型的带可更换耗能段的桥梁横向防落梁限位装置。分别以可更换耗能段的腹板厚度、腹板高度及安装位置等为参数，采用有限元软件ABAQUS建立了10个不同参数的装置模型并对其开展拟静力仿真试验，探讨其工作机理，验证其可更换的设计思想并剖析其破坏机理，研究各参数对装置滞回曲线、承载力、延性和耗能能力的影响规律。结果表明:该装置可通过先可更换耗能段破坏再竖板破坏达到多道设防和分级耗能的目的，且整个加载过程中装置的滞回曲线饱满、稳定、无明显捏拢，表现出良好的耗能能力；随着可更换耗能段腹板厚度的增加，装置屈服承载力、极限承载力、屈服位移、极限位移以及延性系数逐渐增大，耗能能力逐渐增强；可更换耗能段高度对装置屈服承载力影响不显著；随着可更换耗能段高度的增加，装置极限承载力逐渐增大，装置屈服位移先增大后减小，装置极限位移整体呈下降趋势，装置的延性系数和耗能能力逐渐减小；可更换耗能段的安装高度对装置屈服承载力和耗能能力的影响无统一规律，但与装置的屈服位移、极限位移及延性系数成负相关。基于本析结果，建议装置在满足承载力要求的前提下，应尽量选取可更换耗能段腹板厚度较厚、高度较小和安装位置较低的参数进行设计。  相似文献   

Response to the paper by H. Zia,B. Lecampion “Explicit versus implicit front advancing schemes for the simulation of hydraulic fracture growth” (Int. J. Numer. Anal. Methods Geomech., 2019, 43 (6), 1300–1315)     

Aleksandr Linkov 《国际地质力学数值与分析法杂志》2020,44(16):2254-2259

The response presents three comments, which (i) explain theoretical background for the success of the explicit front advancing scheme by Zia and Lecampion (comment 1), (ii) suggest possible extensions (comment 2), and (iii) pay attention on expected limitations of the scheme to be checked by the authors in numerical experiments (comment 3). The response does not intend to present novel results: it is entirely based on known results published in the references cited.  相似文献   

世越号起吊姿态敏感性分析与方案选择     

姚宗  蒋岩  王伟平  陈世海 《海洋工程》2018,36(2):135-142

韩国世越号打捞是世界上首次利用托底钢梁原状态整体起吊难船出水的工程。客滚难船装载的货物容易在沉没后发生移位,上层建筑长时间沉没海底后发生泥沙淤积导致难以准确估计整船的重量重心及浮力浮心的位置。利用水池模型试验和数值计算两种方法分别对大型浮吊船单臂架打捞法和双驳船抬吊打捞法进行了难船姿态受重心位置偏移的敏感性分析。水池模型试验中发现,用大型浮吊船单臂架打捞法,世越号的姿态受其重心位置偏移非常敏感,容易发生侧翻;而用双驳船抬吊打捞法,世越号的姿态受其重心位置的影响非常有限,难船和抬浮驳船都可以保持一个较好的姿态。对比水池模型试验的结果,由于难以计及托底钢梁的翘动和滑动现象,数值计算中得到的难船起吊姿态值偏小。双驳船抬吊打捞法被选为打捞世越号的施工方案,其对难船重心位置偏移不敏感的特性得到了现场实证。这个特点为世越号的成功打捞出水起到了关键作用。  相似文献   

Divergence and flow direction as indicators of subsurface heterogeneity and stage‐dependent storage in alluvial floodplains          下载免费PDF全文

D. M. Heeren  G. A. Fox  A. K. Fox  D. E. Storm  R. B. Miller  A. R. Mittelstet 《水文研究》2014,28(3):1307-1317

Assuming homogeneity in alluvial aquifers is convenient, but limits our ability to accurately predict stream‐aquifer interactions. Research is needed on (i) identifying the presence of focused, as opposed to diffuse, groundwater discharge/recharge to streams and (ii) the magnitude and role of large‐scale bank and transient storage in alluvial floodplains relative to changes in stream stage. The objective of this research was to document and quantify the effect of stage‐dependent aquifer heterogeneity and bank storage relative to changes in stream stage using groundwater flow divergence and direction. Monitoring was performed in alluvial floodplains adjacent to the Barren Fork Creek and Honey Creek in northeastern Oklahoma. Based on results from subsurface electrical resistivity mapping, observation wells were installed in high and low electrical resistivity subsoils. Water levels in the wells were recorded real time using pressure transducers (August to October 2009). Divergence was used to quantify heterogeneity (i.e. variation in hydraulic conductivity, porosity, and/or aquifer thickness), and flow direction was used to assess the potential for large‐scale (100 m) bank or transient storage. Areas of localized heterogeneity appeared to act as divergence zones allowing stream water to quickly enter the groundwater system, or as flow convergence zones draining a large groundwater area. Maximum divergence or convergence occurred with maximum rates of change in flow rates or stream stage. Flow directions in the groundwater changed considerably between base and high flows, suggesting that the floodplains acted as large‐scale bank storage zones, rapidly storing and releasing water during passage of a storm hydrograph. During storm events at both sites, the average groundwater direction changed by at least 90° from the average groundwater direction during baseflow. Aquifer heterogeneity in floodplains yields hyporheic flows that are more responsive and spatially and temporally complex than would be expected compared to more common assumptions of homogeneity. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献