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91.
Xuanmei Fan David G. Rossiter Cees J. van Westen Qiang Xu Tolga Görüm 《地球表面变化过程与地形》2014,39(14):1913-1926
In this study we develop an empirical method to estimate the volume threshold for predicting coseismic landslide dam formation using landscape parameters obtained from digital elevation models (DEMs). We hypothesize that the potential runout and volume of landslides, together with river features, determine the likelihood of the formation of a landslide dam. To develop this method, a database was created by randomly selecting 140 damming and 200 non‐damming landslides from 501 landslide dams and > 60 000 landslides induced by the Mw 7.9 2008 Wenchuan earthquake in China. We used this database to parameterize empirical runout models by stepwise multivariate regression. We find that factors controlling landslide runout are landslide initiation volume, landslide type, internal relief (H) and the H/L ratio (between H and landslide horizontal distance to river, L). In order to obtain a first volume threshold for a landslide to reach a river, the runout regression equations were converted into inverse volume equations by taking the runout to be the distance to river. A second volume threshold above which a landslide is predicted to block a river was determined by the correlation between river width and landslide volume of the known damming landslides. The larger of these two thresholds was taken as the final damming threshold. This method was applied to several landslide types over a fine geographic grid of assumed initiation points in a selected catchment. The overall prediction accuracy was 97.4% and 86.0% for non‐damming and damming landslides, respectively. The model was further tested by predicting the damming landslides over the whole region, with promising results. We conclude that our method is robust and reliable for the Wenchuan event. In combination with pre‐event landslide susceptibility and frequency–size assessments, it can be used to predict likely damming locations of future coseismic landslides, thereby helping to plan emergency response. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
92.
Issa E. Issa 《水文科学杂志》2013,58(7):1456-1466
AbstractMosul Dam is one of the biggest hydraulic structures in Iraq. Its storage capacity is 11.11 × 109 m3 at a maximum operation level of 330 m a.s.l. The dam became operational in 1986 and no survey has been conducted to determine its storage capacity and establish new operational curves since this date. A topographic map of scale 1:50 000 dated 1983 was converted into triangulated irregular network (TIN) format using the ArcGIS program to evaluate the operational curves. Then the reservoir was surveyed in 2011 to establish the reduction in its storage capacity and to develop new operational curves. The results indicated that the reduction in the storage capacity of the reservoir was 14.73%. This implies that the rate of sedimentation within the reservoir was 45.72 × 106 m3 year?1. These results indicate that most of the sediment was deposited within the upper zone of the reservoir where the River Tigris enters the reservoir.Editor D. KoutsoyiannisCitation Issa, E.I., Al-Ansari, N., and Knutsson, S., 2013. Sedimentation and new operational curves for Mosul Dam, Iraq. Hydrological Sciences Journal, 58 (7), 1456–1466. 相似文献
93.
Molly Pohl 《The Professional geographer》2004,56(3):422-431
Dams are a major source of fragmentation and degradation of rivers. Although substantial research has been conducted on the environmental impacts of large structures in the United States, smaller dams have received less attention. This study evaluated the impact of two dams of moderate size, the Elwha Dams, on the downstream channel system using field data collection at river cross‐sections. The relationship of average boundary shear stress (τo) to critical shear stress (τcr) served as the basis for determining channel bed material mobility under the two‐year and ten‐year flood events. The channel had the greatest channel bed mobility at the natural cross‐section upstream from the dams, low bed mobility between the structures, and an increase in channel bed mobility in the low gradient river segment near the mouth of the river. Low bed mobility tended to be associated with a lack of channel system complexity, including reduction or loss of bars and low alluvial terraces and their associated young riparian communities. Although these run‐of‐the‐river dams do not modify streamflow greatly, the loss of sediment from the channel system has had a substantial impact on bed mobility and geomorphic and biotic complexity of the Elwha River. 相似文献
94.
结合具体工程实例介绍了当前城市中小河道测量工程中常见水工建(构)筑物的类型、调查量测内容及对应精度指标、外业测绘取舍及内业成图表示方法等,特别是根据实地水工建(构)筑物的规模大小、复杂程度,探讨了对其进行调查测绘的技术方法,并结合CAD绘图系统提出了相应的解决办法. 相似文献
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98.
Doan Van Binh Sameh A. Kantoush Tetsuya Sumi Nguyen Phuong Mai Trieu Anh Ngoc La Vinh Trung Tran Dang An 《水文研究》2021,35(2):e14030
The hydrogeomorphology of the Vietnamese Mekong Delta (VMD) has been significantly altered by natural and anthropogenic drivers. In this study, the spatiotemporal changes of the flow regime were examined by analysing the long-term daily, monthly, annual and extreme discharges and water levels from 1980 to 2018, supported by further investigation of the long-term annual sediment load (from the 1960s to 2015), river bathymetric data (in 1998, 2014 and 2017) and daily salinity concentration (from the 1990s to 2015) using various statistical methods and a coupled numerical model. Then, the effects of riverbed incision on the hydrology were investigated. The results show that the dry season discharge (i.e., in March–June) of the Tien River increased by up to 23% from the predam period (1980–1992) to the postdam period (1993–2018) but that the dry season water level at My Thuan decreased by up to −46%. The annual mean and monthly water levels in June at Tan Chau and in January and June–October at My Thuan in the Tien River decreased statistically, even though the respective discharges increased significantly. These decreased water levels instead of the increased discharges were attributed to the accelerated riverbed incision upstream from My Thuan, which increased by more than three times, from a mean rate of −0.16 m/year (−16.7 Mm3/year) in 1998–2014 to −0.5 m/year (−52.5 Mm3/year) in 2014–2017. This accelerated riverbed incision was likely caused by the reduction in the sediment load of the VMD (from 166.7 Mt/year in the predam period to 57.6 Mt/year in the postdam period) and increase in sand mining (from 3.9 Mm3 in 2012 to 13.43 Mm3 in 2018). Collectively, the decreased dry season water level in the Tien River is likely one of the main causes of the enhanced salinity intrusion. 相似文献
99.
Peter R. Robichaud Sarah A. Lewis Robert E. Brown Edwin D. Bone Erin S. Brooks 《水文研究》2020,34(23):4431-4445
Continuing long and extensive wildfire seasons in the Western US emphasize the need for better understanding of wildfire impacts including post-fire management scenarios. Advancements in our understanding of post-fire hillslope erosion and watershed response such as flooding, sediment yield, and debris flows have recently received considerable attention. The potential impacts of removing dead trees, called salvage logging, has been studied, however the use of remotely sensed imagery after salvage logging to evaluate spatial patterns and recovery is novel. The 2015 North Star Fire provided an opportunity to evaluate hillslope erosion reduction using two field experiments and coincidental remotely sensed imagery over 3 years. Simulated rill experiments with four flow rates were used to quantify hillslope erosion on skidder trails with and without added logging slash compared with a burned-only control. Seven replicated hillslope silt fence plots with the same treatments were also evaluated for natural rainfall events. WorldView-2 satellite imagery was used to relate ground cover and erodible bare soil between the two experiments using multi-temporal Normalized Differenced Vegetation Index (NDVI) values. Results indicate that the skid trails produced significantly more sediment (0.70 g s−1) than either the slash treated skid trail (0.34 g s−1) or controls (0.04 g s−1) with the simulated rill experiment. Similarly, under natural rainfall conditions sediment yield from hillslope silt fence plots was significantly greater for the skid trail (3.42 Mg ha−1) than either the slash treated skid trail (0.18 Mg ha−1) or controls (0 Mg ha−1). An NDVI value of 0.32 on all plots over all years corresponded to a ground cover of about 60% which is an established threshold for erosion reduction. Significant relationships between NDVI, ground cover, and sediment values suggest that NDVI may help managers evaluate ground cover and erosion potential remotely after disturbances such as a wildfire or salvage logging. 相似文献
100.
有效应力参数的合理确定是非饱和土有效应力研究的重要内容。然而,现有的有效应力参数未能较好地考虑孔隙水的微观赋存形态对有效应力的影响。为此,分析了孔隙水的微观赋存形态,明确了孔隙水可分为收缩膜、吸附水和毛细水,建立了非饱和粉土的扩展三相孔隙介质模型,即孔隙气、毛细水和广义土骨架。基于该模型,采用分相平衡分析法,推导了非饱和粉土的有效应力方程,该方程通过采用毛细水有效饱和度合理地考虑了毛细水对有效应力的影响。依据推导的有效应力方程,提出了非饱和粉土的抗剪强度公式。采用5种不同围压下重塑非饱和粉质黏土试验数据验证了提出的公式。结果表明:与现有的抗剪强度公式相比,本次提出的公式更好地预测了重塑非饱和粉质黏土的抗剪强度随基质吸力的变化规律。因此,运用提出的抗剪强度公式评价非饱和土边坡稳定性、地基承载力和挡土墙稳定性将会取得更好的效果。 相似文献