ENVIRONMENTAL DESIGNS FOR STREAMBANK PROTECTION PROJECTS1

ABSTRACT: Streambank protection projects are intended to prevent streambank erosion, thereby preventing streambank failure and maintaining a desirable channel alignment. Streambank erosion is a natural process of unaltered, dynamic river systems, and protection projects seek to impose stability on this natural system. The environmental impacts of such projects are primarily changes to terrestrial and aquatic habitats and to aesthetics. Adverse environmental impacts have been minimized and enhancement of existing habitat and aesthetics have been achieved through the development of new, innovative designs or modifications to existing designs and through use of construction and maintenance practices that promote habitat and aesthetics. Designs based on channel flow characteristics, e.g., revetments using a variety of structural materials, can result in preservation of wildlife habitat by reducing the use of structural protection by matching the erosion potential of flow at the bank with the protection capability of the materials used. Designs based on streambed stabilization prevent bank failure caused by bank undermining, result in preservation or establishment of streamside vegetation, and enhance aesthetics. Protection schemes that manage and preserve floodplains, berms, and riparian areas preserve the natural condition of the floodplain area. Designs based on deflection of erosive flows, e.g., dikes, minimize disturbance to the bank vegetation and create low-velocity aquatic habitats. Use of vegetation for bank protection is most effective when used in combination with structural components. Construction and maintenance practices can be scheduled and modified to minimize impacts to floodplain areas and to enhance wildlife habitat while preserving the integrity of the protection structure.     

A DYNAMIC SYSTEM MODEL FOR SIMULATING SEDIMENT DISCHARGE1

ABSTRACT: A dynamic sediment discharge model was developed and proposed for the simulation of watershed systems. It war developed from an expansion of splash and flow erosion relationships under steady state conditions. It was described as a general erosion model that can be reduced to forms comparable to many conceptual soil erosion and sediment yield models. The model incorporates eight parameters such as rainfall intensities, runoff rates, and previous sediment discharges. The model was tested with two small watersheds with simulation results which were very satisfactory compared to the data.     

AGRICULTURAL CONSERVATION PROGRAM: AN EVALUATION1

The Agricultural Conservation Program (ACP), is undergoing a new, rigorous evaluation to determine its effectiveness in conserving the Nation's agricultural soils and waters. ACP deals with many types of conservation practices, but the focus here is on the evaluation of soil and water related practices. ACP has depended heavily on the State and private forestry services, Soil Conservation Service, and the Cooperative Extension Services, for technical expertise. Thus, the process is an evaluation of the effectiveness of a “team of agencies,” as well as of the program itself. Results of the evaluation have helped to develop new thrusts which have moved ACP further into the position of treating the total conservation problem. Phase I has its limitations. It did not address the impact of wind erosion, water quality, change in productive capacity, soil quality, wildlife habitat, off site and farm income impacts. It does show that ACP has and is doing a very good job in meeting its stated purposes. It is clear that ACP's effectiveness can be improved with more and better advanced planning and more intensive use of soil maps, the USLE, and other scientific tools. ACP is headed in this direction.     

降雨条件下岩溶地下水微量元素变化特征及其环境意义

对降雨期间青木关岩溶地下河水的化学特征进行连续监测,获取了Ba、Sr、Fe、Mn、Al这5种微量元素及其他常量元素质量浓度的高分辨率数据.运用相关性分析和浓度变化曲线分析微量元素来源及其迁移路径,并结合流域地质背景探讨地下河微量元素变化特征的形成过程.研究发现,Ba和Sr元素为碳酸盐岩溶解的产物,储存于岩石裂隙、孔隙等介质中,经扩散作用进入地下河,质量浓度变化较小;而Fe、Mn、Al均来源于土壤,其中Fe、Al元素主要通过落水洞直接进入地下河,而Mn则通过土壤-岩石多孔介质补给地下河,三者浓度变化很大,对降雨响应强烈.结果表明,5种微量元素质量浓度均低于1 mg·L-1,Fe、Mn、Al元素最高质量浓度均超过饮用水限值.地下河Al、Fe元素质量浓度变化在一定程度上指示着水土流失和水质变化状况,因此有必要加强落水洞附近的环境保护和治理,从源头控制污染源.     

模拟条件下侵蚀-沉积部位土壤CO2通量变化及其影响因素

了解土壤侵蚀与沉积对土壤CO_2通量的影响有助于正确评价侵蚀区域土壤和大气之间CO_2交换过程与机制.本试验于2014和2015年雨季(7~9月)在长武农田生态系统国家野外站进行,利用土壤碳通量测量系统LI-8100(LI-COR,Lincoln,NE,USA)和土壤温度及水分数据采集器(EM50,DECAGON,USA),测定侵蚀和沉积地貌下的土壤CO_2通量、土壤水分和温度,并采集径流泥沙.结果表明:1侵蚀区和沉积区土壤CO_2通量均值依次为1.05μmol·(m~2·s)~(-1)和1.38μmol·(m~2·s)~(-1),沉积区较侵蚀区增幅达31%(P0.05);沉积区土壤CO_2通量温度敏感性(8.14)是侵蚀区(2.34)3倍以上.2侵蚀区与沉积区土壤水分均值分别为0.21 m~3·m~(-3)和0.25 m~3·m~(-3),沉积区较侵蚀区提高19%(P0.05).尽管侵蚀区较沉积区土壤温度稍有提高(7%),但差异不显著.3泥沙中有机碳平均含量(7.26 g·kg~(-1))较试验之初(6.83 g·kg~(-1))提高6%.4土壤水分和土壤有机碳(SOC)在侵蚀区和沉积区的重新分布对土壤CO_2通量空间变异有重要影响.     

沿海城市气候特征对城市雕塑景观侵蚀程度差异分析研究

建筑物集中造成城市空间单一、枯燥和拥挤,城市雕塑作品可带来美化和装饰的作用.以沿海城市的城市雕塑景观为探究对象,研究在沿海气候特征下雕塑的侵蚀程度差异.首先,针对制作雕塑景观的原料砂岩,需进行侵蚀作用模拟实验,选取城市雕塑砂岩样本在风驱雨模拟条件下进行风洞侵蚀实验及水岩作用实验;然后,通过对砂岩雕塑样本实现风洞侵蚀模拟实验后,可获知侵蚀量伴随风速增强而增大,对砂岩实现室内水岩作用实验后可知矿物转化量增加,产生矿物量越多表明岩体的抗侵蚀能力越低,会增加雕塑侵蚀程度.通过利用模拟实验实现了对城市雕塑景观侵蚀程度的分析,为保护雕塑作品提供数据支持.     

云南省水土流失DPSIR模型指标体系的构建

根据云南省的立地条件及可获取性原则建立了云南省水土流失评价模型DPSIR的指标体系（16个指标）,并初步分析了各指标的时间变化特征,为进一步定量评估云南省水土流失奠定了基础。     

黄土高原清水河流域土地利用/覆盖和降雨变化对侵蚀产沙的影响

近50 a来,在气候变化和生态恢复与治理工程实施的背景下,黄土高原的侵蚀产沙特征发生了明显的变化。以黄土高原典型中尺度流域清水河流域(面积436 km2)为研究对象,利用1959、1986、2007年的土地利用解译结果和1960—2005年该流域实测输沙和降水资料,采用非参数Mann-Kendall趋势分析法和滑动t检验法研究了该流域年输沙量、降雨量的变化趋势和突变点,并与通用土壤流失方程相结合分析了该流域土地利用和降雨变化对输沙量变化的贡献率。结果表明:该流域年输沙量47 a间有显著的下降趋势,突变点位于1980年;降雨量没有明显的趋势性变化,极端降雨指数下降。降雨因素对输沙量减少的贡献率为9.89%,土地利用的贡献率为90.11%,土地利用变化中工程措施淤地坝的贡献率为5.56%,植被变化的贡献率为84.55%。该流域47 a间乔木林地面积增加了944.27%,灌木林地增加了19.33%,表明清水河流域林地面积增加是导致输沙量减少的主要原因。     

Spatial and long-term variability of soil loss due to crop harvesting and the importance relative to water erosion: A case study from Belgium

The harvest of crops such as sugar beet (Beta vulgaris L.), potato (Solanum tuberosum L.), leek (Allium porrum L.) and carrot (Daucus carota L.) causes soil loss from arable land because soil adhering to the crop and soil clods that failed to be separated by the harvesting machine, are exported from the field together with these harvested crops. These soil losses can be of the same order of magnitude as soil losses caused by water erosion processes, but are often neglected in soil erosion research. In this article we developed a methodology to investigate the spatial and long-term (1846–2004) variability of soil loss due to crop harvesting (SLCH) in Belgium and the spatial distribution of the importance of SLCH relative to soil losses caused by water erosion processes in Flanders. The study is based on long-term time series of soil tare data of crop processing factories and area and crop yield statistics. Until the middle of the 20th century, potato and roots and tubers grown as second crop, had the largest share in the SLCH-crop growing area in Belgium. Sugar beet gained importance from the end of the 19th century onwards and has now, of all SLCH crops, the largest growing area. We could estimate that, partly due to increasing crop yields and the mechanisation of the harvesting process, SLCH per hectare of cropland increased from 0.4 Mg ha⁻¹ year⁻¹ in 1846 to 2.4 Mg ha⁻¹ year⁻¹ in the 1970s and early 1980s. Since then mean annual soil losses decreased again to 1.8 Mg ha⁻¹ year⁻¹ in 2004. It was assessed that total yearly SLCH in Belgium rose from more than 575,000 Mg in the middle of the 19th century to more than 1.7 × 10⁶ Mg in the 1970s and early 1980s, while current SLCH values are 1.4 × 10⁶ Mg. We estimated that since 1846, more than 163 × 10⁶ Mg soil was exported from cropland in Belgium through this erosion process, which corresponds to 109 hm³ or an average soil profile truncation of 1.15 cm. Average sediment export from cropland in Flanders was 3.7 Mg ha⁻¹ year⁻¹ in 2002, of which 46% was due to SLCH and 54% was due to water erosion processes. The relative importance of SLCH varied, depending on the agricultural region, between 38% and 94%.     

Environmental cross-compliance mitigates nitrogen and phosphorus pollution from Swiss agriculture

In 1993 the Swiss agricultural policy was revised with – amongst other goals – the objective of improving the environmental performance of agriculture. A voluntary agri-environmental scheme to promote integrated production (IP) was introduced. In 1999 the IP standards were integrated in cross compliance requirements and termed Proof of Ecological Performance (PEP). We evaluated the effectiveness of this policy in terms of reducing diffuse nitrogen (N) and phosphorus (P) pollution of ground and surface water. We combined monitoring schemes covering the reference period from before the introduction of IP/PEP (1990–1992) with the evaluation of cause/effect relationships in selected case-study areas. The evaluation showed an overall reduction of diffuse N and P pollution from agriculture even though some goals were not reached. Nitrate leaching declined, but only a 3–4 mg L⁻¹ reduction was observed rather than the intended decrease of 5 mg L⁻¹. The P pollution of surface waters from agriculture decreased by only 10–30% instead of 50%. The intended reduction of the nitrogen surplus of Swiss agriculture by 33% was not attained, but the P surplus of Swiss agriculture was more than halved. IP/PEP practices that improved N and P management included reduced N and P fertiliser inputs and pig and poultry feedstuffs with reduced N and P contents, both of which are a consequence of the requirement of equilibrated farm nutrient balances, as well as increased use of cover cropping and of conservation tillage systems.