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1.
The western interior portions of Puerto Rico offer optimal climatic conditions for coffee cultivation. However, land and water degradation result when abrupt topographic relief and high annual rainfall combine with forest conversion for coffee farming. Small‐scale rainfall simulation experiments were conducted to quantify runoff and erosion from four land surface types (i.e., mulched, weed‐covered, and bare soils under active cultivation, and unpaved roads) representative of coffee farms in Puerto Rico. Results show that mulch‐covered soils had runoff coefficients similar to those from undisturbed forested conditions (~4%), and that they eroded at rates about a quarter of those for bare cultivated soils. Weed‐covered soils had surprisingly high runoff coefficients (~70%), yet their erosion rates were only three‐fourths of those for bare soils. Annualized erosion rates from unpaved roads were 65 Mg ha−1 y−1, or ten times greater than bare soils and about a hundred times higher than weed‐ or mulch‐covered surfaces. Farm‐scale sediment production estimates amount to ~11 Mg ha−1 y−1, about two‐orders of magnitude higher than under forested conditions. At the farm‐scale, only 2 – 8% of the total sediment is potentially attributable to cultivated hillslopes. In contrast, unpaved roads may account for over 90% of the sediment budget, even though they comprise only 15% of the farm surface area. Therefore, while providing mulch or a vegetative cover to bare cultivated soils should be part of effective soil management, mitigating the effects of coffee cultivation on downstream water resources must focus on the unpaved road network as the primary sediment source. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

2.
为研究矿区土质道路径流产沙及细沟形态发育特征,在野外调查的基础上,设计坡度(3°、6°、9°、12°)和雨强(0.5、1.0、2.5、2.0、2.5、3.0 mm/min)2个处理,在野外建立不同坡度的道路小区,采用人工模拟降雨的方法,测定了不同处理道路径流产沙参数和细沟形态指标。结果表明:1)各坡度道路径流率为1.12~8.24 L/min,与雨强线性关系极显著,随坡度变化不显著;除0.5 mm/min雨强3°~9°坡及1.0 mm/min雨强3°坡道路径流流态为层流外,其余为紊流,雨强-坡度交互作用(I×S)对流态影响显著;阻力系数只与坡度相关。2)各坡度道路剥蚀率为0.92~324.46 g/(m2·s),与雨强、坡度和径流率呈极显著幂函数关系(R2=0.968,P0.01),道路土壤发生剥蚀的临界剪切力和临界径流功率分别为2.15 N/m2和0.41 W/(m2·s)。3)3°道路以片状侵蚀为主,6°~12°道路细沟发育,细沟宽深比、复杂度、割裂度和细沟密度分别为1.80~3.75、1.07~1.55、0.20%~10.33%和0.067~2.01 m/m2,细沟发育程度是雨强和坡度交互作用(I×S)的结果。4)6°~12°道路细沟侵蚀量占总侵蚀量比例为18.0%~57.16%,总侵蚀量与细沟宽深比、细沟复杂度、细沟割裂度和细沟密度均呈显著的函数关系(R2=0.35~0.96,P≤0.01),割裂度是影响土质道路总侵蚀量的最佳细沟形态因子。结果可为矿区土质道路水土保持工程设计及生产安全提供参数支持。  相似文献   

3.
神府东胜煤田是世界7大煤田之一,在开发建设过程中造成了严重的水土流失,其中非硬化路面水土流失是其重要的组成部分.采用野外模拟降雨试验,研究非硬化路面的侵蚀产流、产沙规律以及二者之间的关系.结果表明:非硬化路面的径流含沙量过程曲线包括平缓型、多峰型、单峰型3种类型,侵蚀速率随时间变化过程可分为快速增长阶段、波动起伏阶段以及稳定阶段;非硬化路面的产流时间随降雨强度的增大呈幂函数减小,随坡度的增大呈先增大后减小的抛物线趋势;径流率随降雨强度的增大而增大,拟合关系式为r=2.5961 -0.431;产沙量与径流量之间呈幂函数关系,其关系式为M,=0.223 9W1.9462.研究结果可为矿区水土流失预测和治理提供依据.  相似文献   

4.
非硬化路面侵蚀产沙规律野外模拟试验   总被引：4，自引：2，他引：2  
为了科学治理非硬化路面水土流失,采用野外放水冲刷试验,对非硬化路面侵蚀产沙规律进行了试验研究。结果表明,同一坡度不同放水流量与同一放水流量不同坡度条件下,非硬化路面产沙随时间的变化形式均有3种,分别为平缓型、多峰型和单峰型。对同一路面不同观测断面的产沙量分析发现,产沙量沿坡面的空间变化形式分别为波动式减小、逐渐式减小和先增大后减小。、得出平均含沙量与放水流量呈对数相关,产沙率与放水流量、平均含沙量与坡度、产沙率与坡度均呈直线相关。以期为非硬化路面的水土流失预测和治理提供科学依据。  相似文献   

5.
农村土质道路路面形态对道路侵蚀的影响   总被引：2，自引：0，他引：2  
路面形态作为道路微结构的表现形式,改变道路降雨侵蚀特征,对调节道路系统水沙传递过程有重要意义。本文以拱形、侧向形、平直形、凹形等4种常见路面形态为研究对象,通过室内模拟降雨试验,研究坡度（5°、10°、15°）及路形差异下,道路侵蚀特点。结果表明：路形对产沙的影响高于产流,路形通过改变路面径流的水力学特征来改变产沙特性;在坡度10°和15°时,凹形路面径流流态为急流,流速最大,土壤侵蚀率显著高于其他路形,且侵蚀泥沙颗粒粒径较大;在坡度5°和10°时,拱形和平直形路面水流流态为缓流,拱形路面产流产沙能力最弱,抵抗降雨侵蚀的能力最好。凹形和平直形路面对坡度的敏感性较高,随着坡度提升,产沙量和水流能量均有大幅提高,坡度对拱形和侧向形影响较弱。路形差异导致侵蚀特征迥异,在道路设计建设过程中,科学的路形搭配和“路-渠”组合能有效防治道路侵蚀,降低道路建设对生态环境的影响,该研究可为农村低等级道路建设和维护提供参考。  相似文献   

6.
Unpaved road erosion after heavy storms in mountain areas of northern China   总被引：2，自引：0，他引：2  
More frequent extreme rainfall events associated with global climate change cause greater challenges for soil conservation. Severe erosion occurs on many unpaved roads since these structures create important water flow paths during heavy storms. The present research aimed to investigate the intensity and influencing factors of unpaved road erosion under varied land use and management conditions (sloping cropland, terraced cropland, forest & grass). The erosion occurred in the watersheds contributing runoff water to roads after the greatest rainfall event recorded in the mountain area of northern China caused by Typhon Lekima. The research was conducted in an agricultural-forest-dominated watershed based on field investigation and UAV-based image analysis. A road erosion level classification standard was given according to the occurrence of rills, ephemeral gullies, and gullies. Significant erosion happened on 67% of the unpaved roads; 42% of them suffered moderate to severe erosion in which ephemeral gullies or gullies developed. The average erosion amount from these roads was 2280.75 t ha-1 and was significantly influenced by the watershed land use type and management. The dominant factor governing unpaved road erosion associated with terraced cropland was vegetation coverage on roads. Drainage area was the most important factor for road erosion in sloping cropland and forest & grass land, and road gradient was also a critical factor. Terraces, and forest & grass in drainage areas significantly reduced unpaved road erosion by 85% and, 47%, respectively, compared to sloping cropland. More integrated measures should be used to prevent unpaved road erosion. The results of this research can be applied to road protection against erosion in heavy storms.  相似文献   

7.
非硬化路面与原生地面侵蚀水动力参数对比研究   总被引：2，自引：1，他引：1  
非硬化路面是神府煤田重要的侵蚀单元,其侵蚀过程和方式与原生地面存在一定差别。通过野外人工模拟降雨试验,对比分析了非硬化路面和原生地面水沙响应的过程和机制。结果表明:(1)非硬化路面径流主要为过渡流,原生地面主要为层流,且均为缓流;(2)非硬化路面水流流速、剪切力、佛汝德数、雷诺数、功率大于原生地面,曼宁系数、达西系数小于原生地面;(3)非硬化路面水力参数随坡度、雨强变化趋势与原生地面不完全一致;(4)非硬化路面产沙量随径流量增大,原生地面产沙量为非硬化路面的0.8%~14%;(5)非硬化路面侵蚀模数对水动力参数响应紧密程度表现为:径流总动能平均水流功率平均水流剪切力。  相似文献   

8.
In an effort to pinpoint the sources of sediment pollution in Lake Victoria, the contribution of sediment from compounds, landing sites, unpaved roads and footpaths is determined in the catchment of Nabera Bay and Kafunda Bay at the northern shore of Lake Victoria in southern Uganda. The volume of soil loss is determined in 36 compounds, 1 school and 1 landing site by comparing the original and current soil surface. The original soil surface is reconstructed using botanical and man-made datable objects. The soil loss rates are calculated by dividing the eroded soil volume by the age of the oldest datable object. Considering all compounds and landing sites in the study area, the average soil loss rate in compounds amounts to 107 Mg ha? 1 year? 1 (per unit compound) and to 207 Mg ha? 1 year? 1 per unit landing site. The soil loss from footpaths and unpaved roads is calculated by multiplying the total length of footpaths and unpaved roads with the average width and soil loss depth. The mean soil loss rate on footpaths is 34 Mg ha? 1 year? 1 and on unpaved roads equals 35 Mg ha? 1 year? 1. Compounds, landing sites, footpaths and unpaved roads occupy a small fraction of the study area (2.2%), but contribute disproportionately to the total soil loss (i.e. 85%) in the study area. It is concluded that compounds, landing sites, footpaths and unpaved roads are very significant sources of sediment pollution to Lake Victoria. This needs to be considered when designing strategies to reduce sediment production in the area.  相似文献   

9.
Unpaved roads play an important role in soil loss in small watersheds. In order to assess the impact of these unpaved roads in the Loess Plateau of China, runoff and sediment yields from road‐related sources must be quantified. Field rainfall simulation experiments were conducted under three slope gradients and five rainfall intensities on unpaved loess roads in a small watershed. Results showed that the runoff generation was very fast in loess road surface (time to runoff < 1 min) and produced a high runoff coefficient (mean value > 0·8). Soil loss rates were decreased as surface loose materials were washed away during a rainstorm. Rainfall intensity, initial soil moisture, and slope gradient are key factors to model surface runoff and sediment yield. Soil loss on loess road surface could be estimated by a linear function of stream power (R2 = 0·907). Four commonly interrill erosion models were evaluated and compared, and the interrill erodibility adopted in the Water Erosion Prediction Project model was determined as 1·34 × 106 (kg s m−4). A new equation taking into account different parameters like rainfall intensity, surface flow discharge, and slope gradient was established. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

10.
为防治农路水土流失,以南方红壤区江西水土保持生态科技园为研究区,通过野外调查选择4种典型农路(裸露土路、碎石道路、泥结石路和植草土路)设置12个原位试验小区,采用人工模拟降雨试验研究3.0mm/min强降雨条件下不同农路水蚀过程及其防蚀效应。结果表明:农路的路面被高强度压实,容重较大,比重也较大。农路路面水分入渗率经历了急剧减小后再稳定的过程,以泥结石路、裸露土路和植草土路表现尤为明显。农路产流后泥沙含量在较短时间内即达到峰值,随即迅速下降。与裸露土质路面相比,泥结石路、碎石道路和植草土路的减水效果并不明显,最大只有14.1%;但减沙效益明显,最低也可达40%左右。该研究结果为南方红壤区坡耕地农路基础设施配套建设和水土保持规划提供了科学参考。  相似文献   

11.
《CATENA》2004,57(1):1-14
The generation of surface runoff and transport of sediment were studied on unpaved forest roads in the Iberian Range (Spain). To this end, a mobile rainfall simulator was used so that information could be compared. Twenty-eight rainfall simulations were carried out on the cutslope (12), sidecast fill (6) and roadbed (10). Under low soil moisture conditions, cutslopes had runoff coefficients of 58%, and overland flow was generated in 3 min. On the sidecast fill and the roadbed, the runoff coefficients were 34% and 46%, respectively. The part of the road that showed the greatest erosion was the cutslope (161 g m−2), where mass wasting and freeze–thaw processes supply loose material to be transported by overland flow. The cutslope soil loss rates exceed those from the sidecast fill and the roadbed by 16 and 11 times, respectively. In these tests, the maximum sediment concentration was recorded in the first few minutes. The concentration reduces with time as a consequence of the exhaustion of loose surface material. Correlation coefficients and regression analysis showed that the gradient, plant cover density and stone cover of the cutslopes, fill areas and roadbeds had statistically significant effects on runoff and erosion. A comparison of these data with others obtained on different land-uses allowed us to conclude that some parts of forest roads have similar hydromorphological behaviour to abandoned fields in mountainous areas and to cereal fields.  相似文献   

12.
A quantitative understanding of both natural and anthropogenic sediment sources is needed to accurately assess and predict the potentially adverse effects of land development on aquatic ecosystems. The main objective of this study was to quantify sediment production and delivery rates in a dry tropical environment on the island of St. John in the eastern Caribbean. One to three years of measurements were used to determine values and empirical functions for estimating sediment production from streambanks, treethrow, undisturbed hillslopes, zero-order sub-catchments, unpaved road surfaces, and road cutslopes. Sediment production also was measured from both undisturbed and roaded first-order sub-catchments.  相似文献   

13.
《CATENA》2005,60(1):59-80
This paper reports the results of a study on how fire effects water and sediment losses in the Central Spanish Pyrenees where land abandonment results in an increase of the scrubland and fire-affected surfaces. In 1991, two plots (control and burnt) were installed to collect runoff, suspended sediments and solutes. One of the plots was burnt (burnt-1) and the other was covered by shrubs and herbs (control). During 1993, another burnt plot was installed (burnt-2). Data was collected from the three plots until 1999 and is used as the basis for assessing the soil erosion changes after the fire. Runoff, solute and suspended sediment concentration and erosion rates were slightly greater during the first 2 years following fire on burnt-1 compared to the control plot. The average runoff coefficients during the 8-year study period were 4.2% and 7%, the total sediment concentrations were 189 and 181 mg l−1, and the erosion rates were 89 and 143 kg ha−1 year−1 for the control and burnt-1 plots, respectively. In contrast, burnt-2 plot responded differently than burnt-1 plot to fire, although these two plots were designed to be replicated treatments. The average runoff coefficient for burnt-2 plot was two times greater than that for the control plot. Likewise, total sediment concentration was 649 mg l−1 and erosion rate was 566 kg ha−1 year−1, which are 3.6 and 4.5 times greater than the control plot. Differences between burnt and control plots were analysed at hourly, daily, monthly and yearly temporal scale. Both burned plots began to recover after the fire. However, burnt-1 plot had a recovery time of 2 years compared to burnt-2 plot; while 7 years after the fire, the runoff sediment concentration and erosion rates from burnt-2 were higher than those for the control plot. Water and sediment losses from the two burnt plots were markedly different.  相似文献   

14.
The measurement of soil erosion rates under natural rainfall conditions is costly and time consuming. Data provided by rainfall simulation and static site measurements can be used to predict erosion rates under natural conditions, however the accuracy of this method is largely untested. This is especially true for erosion rates from unsealed forest roads. In this study, the values for a range of erodibility indices calculated from rainfall simulation experiments are compared to observed erodibility index values from 1 year of detailed in-situ erosion monitoring of seven different forest road types. The prediction of phosphorus generation rates from rainfall simulation and/or soil sampling was also evaluated. The results showed that a series of commonly used erodibility indices such as sediment per unit rainfall, sediment per unit runoff, sediment per unit EI30, and sediment per unit rainfall energy were poorly predicted from the rainfall simulation experiments. Five of the six indices tested substantially overpredicted the observed erodibility at one site, a gravel road subjected to minimal traffic. For the other six road sites predictions were poor and highly variable, the coefficient of efficiency ranging from − 13.32 to 0.17 for these erodibility indices. A modified index, the ratio of sediment per unit rainfall energy to the mean rate of rainfall energy input, was able to predict annual erosion rates from six different road surfaces using rainfall simulation data with a coefficient of efficiency of 0.9. The results indicate that existing erodibility indices are not suitable for predicting observed erosion rates on forest roads using rainfall simulation data as collected in this study. It is argued that the modified index is more suited to sites (such as compacted roads) where interrill processes dominate, and erosion rates are less sensitive to peak flows. With respect to nutrient generation rates, rainfall simulation was able to accurately predict the observed proportion by mass of total phosphorus (TP) in runoff with a coefficient of efficiency of 0.96. Direct soil sampling of the road surface could also be used to predict the proportion by mass of TP in runoff. Concentrations of total nitrogen in forest road materials were found to be at the lower detection limit of the laboratory instruments.  相似文献   

15.
砒砂岩原状坡面不同季节复合侵蚀动力的贡献研究   总被引：3，自引：3，他引：0  
为揭示黄河中游砒砂岩区多动力复合侵蚀的季节变化特征,该研究融合野外原位观测、三维激光扫描仪技术和GIS等多研究手段,基于2018年3月—2019年4月砒砂岩裸坡上3个试验小区的各4期地形点云数据、坡面实测侵蚀量以及研究区气候数据,分析了砒砂岩水蚀、冻融侵蚀、风蚀的季节交互特征,并分离了各侵蚀动力对原状坡面的侵蚀贡献。3个试验小区为水力+冻融+风力复合侵蚀原状小区、水力+冻融复合侵蚀小区和冻融小区,尺寸均为12.5 m×2.5 m。结果表明,3月—6月、11月—翌年4月砒砂岩坡面侵蚀动力以冻融+风力为主,7—10月坡面侵蚀动力以水力为主。在3月—6月、7月—10月、11月—翌年4月3个时段中,水力+冻融+风力原状小区内侵蚀量比例分别为10.58%、76.61%和12.81%,水力+冻融复合侵蚀小区内侵蚀量比例分别为10.43%、78.57%和11%,冻融小区内侵蚀量比例分别为31.90%、28.65%和39.45%。3个时段中,对原状坡面而言,水力侵蚀的贡献率分别为21.85%、71.42%和11.12%,冻融侵蚀的贡献率分别为53.09%、6.58%和54.20%,风力侵蚀的贡献率分别为25.06%、21.99%和34.69%。在3月—6月、11月—翌年4月,冻融侵蚀量最大,水力侵蚀量最小;7月—10月,水力侵蚀量最大,冻融侵蚀量最小。在整个研究期,原状坡面侵蚀量中水蚀占58.45%、冻融和风蚀共占41.55%。2018年各侵蚀动力对坡面的影响程度由大到小依次为水力侵蚀、冻融侵蚀、风力侵蚀。研究结果可为砒砂岩区复合侵蚀综合治理提供理论依据。  相似文献   

16.
Detachment of road surface soil by flowing water   总被引：3，自引：0，他引：3  
An agricultural watershed generally consists of two land use categories, farmland and the unpaved road or path networks with different traffic frequency and size. Road surfaces are quite different from farmland soil in physical properties, resulting in it's distinguish production transportation process. Hydraulic flume experiments were conducted with the flow discharges ranging from 1 to 5 L s− 1 and the slope gradients ranging from 8.8% to 46.6% to simulate the soil detachment process on a road surface and to develop tools in order to calculate detachment rates occurring on that road surfaces. The results illustrate that road surfaces behave characteristically in the runoff detachment and sediment delivery process due to the difference in the bulk density and functions of agricultural soils. The soil detachment rate is closely related to flow depth, slope gradient and other hydraulic parameters such as shear stress, stream power and unit stream power. Multiple non-linear regression analyses indicate that detachment rates for all roads can be accurately predicted by power functions of flow depth and slope gradient. According to the experimental results, stream power was suggested as an indicator to estimate soil detachment rate instead of shear stress in soil erosion models. However, considering the simplicity and availability, power function of flow depth and slope gradient is also recommended to predict detachment rate on the road surfaces.  相似文献   

17.
Energy development in the Bakken and Three Forks formations of the USA has led to an increase in fugitive dust from unpaved roads. A dust abatement alternative that has been considered in this region is oil-well produced waters. The objectives of this study were to compare dust loading at sites abated with produced water to non-abated control sites and to determine if the elemental constituents in released dust are different compared to control roads. Three previously untreated unpaved roads were selected, and passive dust collectors were placed at 10, 20, 40, and 60 m from the road on the downwind side of the dominant prevailing wind in each mile section. Eighty-four days post-application, two sections treated with produced waters failed to reduce dust when compared to the controls. Dust elemental changes were found on two of the three roads. Elements that were found to have differences included Mo, Mn, Fe, As, Au, and Hg. Overall results indicated that oil-well produced water is not effective at controlling road dust. Results of this study are important to road managers who are contemplating the usage of produced waters to reduce dusts from unpaved roads.  相似文献   

18.
This study analyses the spatial variability of runoff and erosion rates in vineyards due to mechanisation works. Runoff samples were collected at three positions in two plots after 33 erosive events in three years (2001, 2003, 2004) with different rainfall patterns. Three replications were considered at each position. Soil properties were evaluated in order to analyse its relationship with runoff and erosion rates. Runoff and erosion rates were, on average, higher in the levelled plot (HD), ranging between 8·4 and 34·3 per cent, than in the non‐levelled plot (LD) ranging between 8·2 and 24·1 per cent. Mean sediment concentration in runoff ranged between 6 and 8 g L−1 in the HD plot and about 4·6 g L−1 in the LD plot, but with high differences within the plot. In the HD plot, runoff‐rainfall rates were significantly higher (at 95 per cent level) in the upper part of the slope and decreased along the slope, while in the LD plot, differences in runoff rates were not significant and similar to those observed in the less disturbed areas of the HD plot. The higher susceptibility to soil sealing in areas where the original topsoil was removed conditioned runoff rates. In the lower part of the HD plot runoff rates were, on average, 20 per cent lower than in the upper part of the slope. In those positions runoff rates up to 79 per cent were recorded. Organic matter content and water retention capacity at different potentials are the soil characteristics related to the differences on runoff and erosion rates in the resulting soils. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

19.
The presence and condition of roadways control the utilization of natural resources, which are associated with direct and indirect impacts on soil erosion in undeveloped countries. This paper addresses the relationship between soil erosion and distance to roadways in Xingguo County, an undeveloped area in Jiangxi Province of South China, for four time periods, 1958, 1975, 1982, and 2000. Soil erosion maps for each time period were interpreted using remote sensing and GIS technology for buffer zones four kilometers wide, subdivided into eight strips, each 0.5 kilometers wide, which were located alongside various types of road classes, namely trunk, town, village, and unpaved. The distribution patterns of various types of erosion were identified by GIS overlay of buffer strips and soil erosion maps. Results demonstrate that soil erosion cases found in buffer zones along both sides of trunk and town roads are the most severe, and areas with severe erosion decrease as distance from the strip to the road increases. However, moderate and slight erosion cases only have a minor relationship to the strip to road distance. There are more severe erosion cases than moderate and light erosion cases alongside village and unpaved roads, but the total area is not distinctly different from moderate and slight erosion cases, and severe erosion cases tend to decrease with an increase in the strip to road distance. Also, areas with severe erosion differentiated by time periods in the strips alongside roadways of all classes, except trunk roads, rank from highest to lowest as follows: 1975, 1958, 1982, and 2000. Notably, severe erosion areas in 1975, 1958 and 1982 are all quite extensive. Soil erosion alongside roadways of various classes is impacted jointly by historical policy, distance to roadways, and landscape. In undeveloped countries and areas, much more attention should be paid to the impacts of road construction, specifically soil erosion associated with road edge construction, and relevant measures for forest resource conservation should be formulated before initiating road construction projects.  相似文献   

20.
草本植物对土质路面径流水动力学特征及水沙过程的影响   总被引：7，自引：2，他引：5  
通过室内人工模拟降雨,研究了草本植物不同覆盖度土质路面的径流水动力学特征以及路面的产流产沙过程。结果表明,路面径流的弗劳德数和雷诺数属层流的急流范畴,并且二者与径流流速及过水断面单位能量相同,均随草本植物覆盖度的增大而减小。而Darcy-weisbach阻力系数以及曼宁糙率系数则均随覆盖度的增大而增大。在不同覆盖度土质路面上,径流量随径流时间急剧增大后趋于稳定,且二者符合移轴双曲线关系,而输沙率则经历了先增大后减小的过程。随着植被覆盖度的增大,土质道路的水分入渗率逐渐增大,而径流量、输沙率及含沙率均逐渐减小。该研究表明土质路面种植的草本植物具有较好的水土保持功能,为阐明草本植物与土壤侵蚀的关系提供了理论依据。  相似文献   

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