Influence of anthropogenic land‐use change on hillslope erosion in the Waipaoa River Basin,New Zealand          下载免费PDF全文

Corina Cerovski‐Darriau  Joshua J. Roering 《地球表面变化过程与地形》2016,41(15):2167-2176

European settlement of the Poverty Bay Region resulted in deforestation and conversion of > 90% of the landscape to pastureland. The resulting loss of vegetation triggered a rapid increase in hillslope erosion as widespread landslide complexes and gully systems developed on weak lithologic units in the Waipaoa Basin. To quantify the rate and volume of historic hillslope degradation, we used a 1956–2010 sequence of aerial photographs for a ~16 km² catchment to map temporal changes in the spatial extent of active landslides. Then we created a ‘turf index’ based on the extent and style of pastoral ground disruption, which correlates with downslope velocity. Based on the movement of trees and other features, we assigned average velocities to the turf classes as follows: (1) minimal disrupted ground: 0.6 m/yr, (2) a mix of disrupted ground and intact blocks: 3.4 m/yr, and (3) no intact blocks or vegetation: > 6 m/yr. We then calculated the average annual sediment flux using these turf‐derived velocities, the width of the landslide‐channel intersection, and an average toe depth of 4.4 ± 1.3 m (mean ± standard deviation [SD]) from 37 field measurements. The resulting catchment averaged erosion rates are (mean ± SD): 29.9 ± 12.9 mm/yr (1956), 28.8 ± 13.7 mm/yr (1969), 13.4 ± 4.9 mm/yr (1979), 17.0 ± 6.2 mm/yr (1988), and 9.9 ± 3.6 mm/yr (2010). Compared with long‐term (post‐18 ka) erosion rates (1.6 mm/yr) and the long‐term uplift rate (~1 mm/yr) for this site, the 50‐year anthropogenically‐driven rate is an order of magnitude larger (~20 mm/yr). Previously, we measured an increase in erosion over the past 3.4 kyr (2.2 mm/yr), and here, we demonstrate this increase could be primarily due to human land‐use change – showing that a century of rapid erosion superimposed on the background geologic rate can profoundly skew the interpretation of erosion rates. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Root properties of vegetation communities and their impact on the erosion resistance of river dikes   总被引：1，自引：0，他引：1       下载免费PDF全文

Wouter Vannoppen  Jean Poesen  Patrik Peeters  Sarah De Baets  Bart Vandevoorde 《地球表面变化过程与地形》2016,41(14):2038-2046

Predicted climate change and the associated sea level rise poses an increased threat of flooding due to wave overtopping events at sea and river dikes. To safeguard the land from flooding it is important to keep the soil erosion resistance at the dikes high. As plant roots can be very effective in reducing soil erosion rates by concentrated flow, the main goal of this study is to explore the variability in root system characteristics of five dike vegetation communities along the Scheldt River (Belgium) and to assess their effectiveness in controlling soil erosion rates during concentrated flow. This study is the first one to investigate systematically the erosion‐reducing potential of the root properties of representative dike vegetation communities in a temperate humid climate. Results show that the presence of Urtica dioica resulted in large differences in root length density (RLD) among dike vegetation communities. Observed RLD values in the topsoil ranged from 129 to 235 km m^‐3 for dike vegetation communities without U. dioica, while smaller values ranging from 22 to 58 km m^?3 were found for vegetation communities with U. dioica. The erosion‐reducing effect of the dike vegetation communities was estimated based on a global Hill curve model, linking the RLD to the soil detachment ratio (SDR; i.e. the ratio of the soil detachment rate for root‐permeated topsoils to the soil detachment rate for root‐free topsoils). Concentrated flow erosion rates are likely to be reduced to 13–16% of the erosion rates for root‐free topsoils if U. dioica is absent compared to 22–30% for vegetation communities with U. dioica. Hence, to maintain a high resistance of the soil against concentrated flow erosion it is important to avoid the overgrowth of grassland by U. dioica through an effective vegetation management. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Predicting reach‐specific properties of fluvial terraces to guide future fieldwork. A case study for the Late Quaternary River Allier (France) with the FLUVER2 model          下载免费PDF全文

Tom Veldkamp  Jeroen M. Schoorl  Willem Viveen 《地球表面变化过程与地形》2016,41(15):2256-2268

Numerical models have not yet systematically been used to predict properties of fluvial terrace records in order to guide fieldwork and sampling. This paper explores the potential of the longitudinal profile model FLUVER2 to predict testable field properties of the relatively well‐studied, Late Quaternary Allier system in France. For the Allier terraces an overlapping ¹⁴C and U‐series chronology as well as a record of ¹⁰Be erosion rates exist. The FLUVER2 modelling exercise is focused on the last 50 ka of the upper Allier reach because for this location and period the constraints of the available dating techniques are tightest. A systematic calibration based on terrace occurrence and thicknesses was done using three internal parameters related to (1) the sediment erodibility; (2) the sediment transport distance; and (3) the sediment supply derived from the surrounding landscape. As external model inputs, the best available, reconstructed, tectonic, climatic and base‐level data were used. Calibrated model outputs demonstrate a plausible match with the existing fluvial record. Validation of model output was done by comparing the modelled and measured timing of aggradation and incision phases for the three locations. The modelled range of landscape erosion rates showed a reasonably good match with existing erosion rate estimates derived from ¹⁰Be measurements of fluvial sands. The quasi‐validated model simulation was subsequently used to make new testable predictions about the timing and location of aggradation and erosion phases for three locations along the Allier river. The validated simulations predict that along the Allier, reach‐specific dynamics of incision and aggradation, related to the variations in sediment supply by major tributaries, cause relevant differences in the local fluvial terrace stratigraphy. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

How is water availability related to the land use and morphology of an inland valley wetland in Kenya?     

《Physics and Chemistry of the Earth》2016

Small inland valley wetlands contribute substantially to the livelihoods of rural communities in East Africa. Their conversion into farmland is driven by water availability. We quantified spatial-temporal dynamics of water availability in a headwater wetland in the humid zone of Kenya. Climatic conditions, soil moisture contents, groundwater levels and discharge data were monitored. A land-use map and a digital elevation model of the valley bottom were created to relate variations in soil moisture to dominant land uses and valley morphology.Upland crops occupied about a third of the wetland area, while approximately a quarter of the wet, central part of the valley bottom was designated for flood-tolerant taro, grown either by itself or in association or in rotation with upland crops. Finally, natural vegetation was found in 3% of the mapped area, mainly in sections with nearpermanent soil saturation.The HBV rainfall-runoff model's overestimation of stream discharge during the long dry season of the hydrological year 2010/2011 can be explained by the strong seasonal impact of water abstraction on the wetland's water balance.Our study vividly demonstrates the necessity of multi-method approaches for assessing the impact of management practices on water availability in valley bottom wetlands in East Africa.  相似文献   

强震动作用下土体非线性动力特征研究发展与展望   总被引：2，自引：2，他引：0  

王玉石  李小军  兰日清  王宁  陈红娟 《震灾防御技术》2016,11(3):480-492

浅地表覆盖土层动力特性对地震动影响显著,软厚土层会明显改变地震动强度及频谱特性。由于观测数据匮乏,强震动作用下土体非线性动力特征研究长期以来均以室内试验为主,但在实验室中难以可靠地模拟实际地震历程中土体承受的加载路径、边界条件、排水条件等复杂因素。近二十年来竖向台阵(至少包含一个地表测点和一个井下基岩测点)记录数据大量增加,为土体非线性动力学研究提供了新的基础数据与发展机遇,使基于现场观测的土体非线性动力特征实证研究成为可能。  相似文献   

两种pH水环境干、湿循环作用对泥质砂岩的侵蚀研究     

王子娟  刘新荣  傅晏  张梁  袁文 《岩土力学》2016,37(11):3231-3239

选取三峡库区某边坡的泥质砂岩为研究对象,分别对pH=3和pH=7溶液下干、湿循环作用的泥质砂岩进行电镜扫描试验（SEM）、4种围压下的三轴压缩试验,通过MATLAB软件处理得到不同pH值和干、湿循环次数下SEM图像的骨架面积比和分形维数。研究表明：在相同的干、湿循环次数下,pH=3酸性环境下的分形维数比pH=7的要大;分形维数与吸水率成正比例相关;与骨架面积、凝聚力成反比例相关;泥质砂岩在干、湿循环作用下的临界骨架面积比为0.55左右;提出了泥质砂岩在干、湿循环作用下的侵蚀度概念,计算并拟合了泥质砂岩的侵蚀度随干、湿循环次数变化的关系曲线;推导出凝聚力的损伤变量公式,为研究不同pH水环境对岩石的侵蚀作用提供参考依据。  相似文献   

Capacity of soil loss control in the Loess Plateau based on soil erosion control degree   总被引：4，自引：0，他引：4  

Haidong Gao  Zhanbin Li  Lianlian Jia  Peng Li  Guoce Xu  Zongping Ren  Guowei Pang  Binhua Zhao 《地理学报(英文版)》2016,26(4):457-472

The capacity of soil and water conservation measures, defined as the maximum quantity of suitable soil and water conservation measures contained in a region, were determined for the Loess Plateau based on zones suitable for establishing terraced fields, forestland and grassland with the support of geographic information system (GIS) software. The minimum possible soil erosion modulus and actual soil erosion modulus in 2010 were calculated using the revised universal soil loss equation (RUSLE), and the ratio of the minimum possible soil erosion modulus under the capacity of soil and water conservation measures to the actual soil erosion modulus was defined as the soil erosion control degree. The control potential of soil erosion and water loss in the Loess Plateau was studied using this concept. Results showed that the actual soil erosion modulus was 3355 t?km^-2?a^-1, the minimum possible soil erosion modulus was 1921 t?km^-2?a^-1, and the soil erosion control degree was 0.57 (medium level) in the Loess Plateau in 2010. In terms of zoning, the control degree was relatively high in the river valley-plain area, soil-rocky mountainous area, and windy-sandy area, but relatively low in the soil-rocky hilly-forested area, hilly-gully area and plateau-gully area. The rate of erosion areas with a soil erosion modulus of less than 1000 t?km^-2?a^-1 increased from 50.48% to 57.71%, forest and grass coverage rose from 56.74% to 69.15%, rate of terraced fields increased from 4.36% to 19.03%, and per capita grain available rose from 418 kg?a^-1 to 459 kg?a^-1 under the capacity of soil and water conservation measures compared with actual conditions. These research results are of some guiding significance for soil and water loss control in the Loess Plateau.  相似文献   

荒漠-绿洲过渡带斑块植被区起沙风对风蚀积沙量的影响   总被引：1，自引：1，他引：0  

胡广录  王德金  廖亚鑫  张宏伟 《中国沙漠》2016,36(4):902-910

以黑河中游荒漠-绿洲过渡带斑块植被区的风蚀积沙观测资料为基础,结合中国生态系统研究网络（CERN）临泽内陆河流域研究站的风况资料,应用地统计学方法对2012-2013年风蚀季（3-8月）的风蚀积沙过程进行分类,并分析起沙风对风蚀积沙量的影响。结果表明：（1）2012-2013年风蚀季风蚀积沙量的空间变异过程分为随机性变异过程（2012年4-7月）和结构性变异过程（2012年8月及2013年3-7月）。（2）在随机性变异过程中,风蚀积沙量与起沙风的风速,风向,风频率依次相关;在结构性变异过程中,风蚀积沙量与起沙风的风向,风速,风频率依次相关。③输沙势（DP）与风蚀积沙量的相关性大小为随机性变异过程>结构性变异过程;在随机性变异过程中,合成输沙势（RDP）与风蚀积沙量无明显相关关系（R²=0.0745）;而在结构性变异过程中,合成输沙势（RDP）与风蚀积沙量的相关系数较高（R²=0.9343）。④在随机性变异过程中,各月风蚀积沙量呈不规则的片状分布;在结构性变异过程中,各月积沙量呈明显的带状分布。  相似文献   

风水复合侵蚀研究进展与展望   总被引：3，自引：1，他引：2  

杨会民  王静爱  邹学勇  史培军 《中国沙漠》2016,36(4):962-971

风水复合侵蚀是干旱,半干旱区一种常见的土壤侵蚀类型,是风水两相外营力相互耦合驱动下发生的地表物质再分配过程。在辨析风水复合侵蚀类型的基础上,将风水复合侵蚀影响因子归结为侵蚀动力因子、土壤抗蚀性因子与干扰因子,并分析了影响因子间的互馈关系;从全球尺度、区域尺度和局地尺度,总结了风水复合侵蚀在空间尺度上的差异;评述了风水共同侵蚀过程中侵蚀力与侵蚀能量的叠加效应,风水交替侵蚀过程中侵蚀力与侵蚀能量的交替性特征,以及下垫面和干扰因子对风水复合侵蚀的响应;阐述了风力与水力侵蚀在总侵蚀量中的贡献比率与两者叠加所产生的耦合效应;认为风水复合侵蚀实验研究是认识风水复合侵蚀过程与机理的基础,应将风水复合侵蚀过程段研究扩展到全过程研究,同时加强下垫面在风水复合侵蚀中的响应机制以及水蚀与风蚀间的抑制效应研究,以期达到全面客观地认识风水复合侵蚀过程与机制的目的。  相似文献   

不同砾石覆盖度戈壁床面风蚀速率定量模拟   总被引：2，自引：2，他引：0  

谭立海  张伟民  屈建军  殷代英  安志山  边凯 《中国沙漠》2016,36(3):581-588

通过风洞实验,利用称重传感器自动记录风蚀观测样方重量变化过程,对供沙条件下不同砾石覆盖度戈壁床面风蚀速率进行了定量模拟研究。结果表明:砾石覆盖度是影响戈壁风蚀速率的关键因子,戈壁床面风蚀速率随砾石覆盖度增加按指数规律递减。各实验风速下,砾石覆盖度>50%时,戈壁床面风蚀速率随砾石覆盖度增加而减小量有限,甚至无风蚀发生;而盖度从10%到50%时,风蚀速率显著减小。因此,两种实验粒径砾石(3 cm与4 cm)至少在50%盖度时才能达到较好的风蚀防治效果。戈壁风蚀防护机理主要是砾石覆盖度的增加增大了砾石间沙粒的临界起动剪切风速,而且减少了作用在砾石间可蚀地表的剪切压。与沙质对照床面相比,10%~90%砾石盖度戈壁床面沙粒临界起动剪切风速增大了0.8~3.4倍,只有0.5％~28%的剪切压作用在砾石间可蚀地表。  相似文献