电磁感应仪EM38用于土壤盐渍剖面分类与评价研究   总被引：9，自引：0，他引：9  

姚荣江  杨劲松  刘广明  邹平  陈小兵 《中国地质灾害与防治学报》2007,18(4):54-59

结合电磁感应仪EM38测量与田间采样,文章分析了黄河三角洲典型区域土壤电导率的剖面分布特征,建立了磁感式表观电导率与土壤电导率间的(多元)回归解译模型,探讨了不同分类方法对土壤盐渍剖面分类结果的准确性,并对典型盐渍剖面类型进行了评价。结果表明:研究区土壤盐分具有较强的表聚性与变异强度;土壤电导率与磁感表观电导率EMh、EMv间呈极显著的相关关系,EMh对浅层土壤电导率的解译精度较高,而EMv对深层土壤电导率的解译精度较高;EMv/EMh法和理论函数法对土壤盐渍剖面的分类结果均具有较高的精度,且理论函数法分类结果的准确性明显优于EMv/EMh法;研究区土壤盐渍剖面可划分为表聚型、底聚型与均匀型,在数量上以表聚型及底聚型为主,其中表聚型与均匀型属于积盐型剖面,底聚型属于脱盐型剖面。该结果对研究黄河三角洲地区土壤盐渍化的发生、机理、预测与评估该地区土壤盐渍化的发生、发展具有重要意义。  相似文献   

Surface properties of stabilizing coastal dunes: combining spectral and field analyses     

NOAM LEVIN  GIORA J. KIDRON†  EYAL BEN-DOR 《Sedimentology》2007,54(4):771-788

The coastal dunes of Israel have been undergoing a process of stabilization since 1948. One of the major features of this process is a change in the surface properties of the dunes – the development of a biological soil crust (BSC), and a change in the properties of the sand grains themselves. In Ashdod, at the southern coastal plain of Israel, sand properties that include the BSC, their fines (silt and clay) content and free iron-oxide (indicating their degree of rubification) have been analysed in detail using field and lab spectroscopy methods. In addition, sand erosion and deposition were measured using erosion pins to determine their effect on the presence of the above-mentioned factors. It was found that the BSC over these dunes is comprised of green algae that differs in its reflectance spectra from cyanobacterial crust, especially in the blue band. The crust was found to be particularly developed in the stable areas (mainly the interdunes) and on the north-facing slopes rather than on the south-facing slopes. A positive correlation was found between the crust fines and chlorophyll content, with stable areas showing more developed BSC. The stable areas showed also a lower albedo and slightly more developed reddish colour, indicating a slightly higher rate of rubification. This study demonstrates that the intensity of sand erosion/deposition rates affects soil properties, with the BSC being the fastest to react to the stabilization process (months to several years), followed by the content of fine particles (several years to a decade), whereas the rubification process is a much weaker marker and may need much longer time periods to develop (decades to centuries).  相似文献   

被动微波反演裸露区土壤水分综述   总被引：4，自引：1，他引：4  

韩念龙  陈圣波  汪自军  包书新  宋金红 《吉林大学学报(地球科学版)》2007,(Z1)

被动微波具有全天候、穿透性以及不受云的影响等特征,使其在反演土壤水分时具有很大的优势。通过研究发现,被动微波遥感是反演土壤水分的各种技术中最有效的方法之一。概括了主要的被动微波传感器并从被动微波遥感的原理出发,针对被动微波遥感裸露区地表随机粗糙面的模型以及土壤水分反演算法作了简要介绍。  相似文献   

气象灾害事件的数学形态学特征及空间表现   总被引：2，自引：1，他引：2       下载免费PDF全文

扈海波王迎春  刘伟东 《应用气象学报》2007,18(6):802-809

几何面特征是气象灾害的主要空间形态表现, 气象要素值的同化结果、下垫面地表类型、人口和财产的聚集特征组合在灾害特征面上的分布情况呈现显著空间差异及分布不均衡。利用空间分析和数学形态学方法, 依据城市地区复杂下垫面所表现的地表土地覆盖类型, 生成数字化动态卷积模板, 对建立在气象要素分布图上的图谱化网格进行动态膨胀和腐蚀操作, 计算结果可图形化表示为气象灾害在城市空间面上的影响图谱, 并以此作为气象灾害在城市地区造成影响的空间评估结果。针对北京1999年7月22日的高温灾害性天气的个例研究结果表明, 靠近或包含“水体”和“绿地”的空间网格区域大多被执行了腐蚀操作, 而建筑用地、道路、水泥地面等分布较集中区域的空间网格, 则被执行了膨胀操作。因此, 采用数学形态学的“面状灾害事件”空间形态特征的演算对表现灾害自然强度及评估多致灾因子下灾害的真实影响情况是非常有效的。  相似文献   

用ERS风散射计数据估算土壤水分方法的研究     

陈权  李震  王磊  魏小兰 《遥感学报》2007,11(6):803-810

欧空局ERS1/2卫星上的风散射计(WSC),分辨率是50km,4天内能覆盖全球超过80%的范围,并可在多角度下对地物目标进行观测。本文研究利用该散射计数据估算土壤水分的方法。首先,利用基于ERS散射计数据建立的全球C波段雷达后向散射系数数据库,根据传统的几何光学模型(GOM),反演得到与土壤含水量密切相关的法线方向Fresnel反射率,并与两个采样点(安多和那曲)上的实测降雨量及土壤水分相对比,证明了ERS散射计数据与土壤水分的高相关性;第二步,以水云模型为基础,结合AIEM模型,发展了一种简化模型来估算土壤水分绝对值,分别利用气象站实测点数据和同时期的Basist湿度指数(BWI)进行验证,表明反演结果能较好反映土壤水分的空间分布状况。  相似文献   

基于支持向量机的遥感大雾判识   总被引：1，自引：0，他引：1  

刘年庆  蒋建莹  吴晓京 《气象》2007,33(10):73-79

提出了一种基于支持向量机的卫星遥感数据大雾判识方法:首先通过对风云1D卫星大雾区域的各通道辐射值出现频次进行概率统计,利用其阈值来粗判识大雾;然后在粗判识的基础上通过支持向量机的方法进行大雾细判识;最后利用腐蚀和膨胀的图像处理技术对判识后的图像进行优化处理。在对我国2006年9-12月的65条监测到大雾的风云1D轨道的探测数据进行分析之后,发现大雾判识结果与专家标记吻合。检验结果表明,利用1、2、4、6、7、10通道组合进行粗判识的结果最好,5交叉正确率为89.9849%,TS评分为74.04%。利用上述方法对个例的分析检验表明,基于支持向量机的遥感大雾判识方法是切实可行的。  相似文献   

Analysis of the impact of conservation measures on stream flow regime in catchments of the Loess Plateau,China   总被引：3，自引：0，他引：3  

Xingmin Mu  Lu Zhang  Tim R. McVicar  Basang Chille  Peng Gau 《水文研究》2007,21(16):2124-2134

Catchments in the Loess Plateau have been under the influence of human activities for centuries. In the last four decades, soil conservation measures have accelerated and intensified. These measures were designed to reduce soil erosion, improve agricultural productivity, and enhance environmental quality. It is important to evaluate the effects of these measures on hydrology in order to develop sustainable catchment management plans in the region. This study evaluated changes in stream flow data for four selected catchments in the Loess Plateau following large‐scale soil conservation measures. The non‐parametric Mann–Kendall test was used to identify trends in annual stream flow and the results showed significant downward trends in three of the four catchments. The Pettitt test indicated that a change point occurred in 1978 in these three catchments. Annual precipitation in all the catchments showed no significant trend during the period of record. Comparison of daily flow duration curves for two 20‐year periods (1957–1978) and (1979–2003) showed significant changes in stream flow regime. Reduction in most percentile flows varied between 20 and 45%, and the reduction in low flows was greatest. Overall, the reductions in daily flow were increasing with time, with significant changes occurring in the 1990s. However, it is not clear whether these catchments have seen the full effects of the soil conservation measures, so the results of this study might underestimate the final impact of soil conservation on stream flow regime. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Soil erosion and sediment interception by check dams in a watershed for an extreme rainstorm on the Loess Plateau,China     

《国际泥沙研究》2020,35(4):408-416

The magnitude of soil erosion and sediment load reduction efficiency of check dams under extreme rainstorms is a long-standing concern. The current paper aims to use check dams to deduce the amount of soil erosion under extreme rainstorms in a watershed and to identify the difference in sediment interception efficiency of different types of check dams. Based on the sediment deposition at 12 check dams with 100% sediment interception efficiency and sub-catchment clustering by taking 12 dam-controlled catchments as clustering criteria, the amount of soil erosion resulting from an extreme rainstorm event on July 26, 2017 (named “7·26” extreme rainstorm) was estimated in the Chabagou watershed in the hill and gully region of the Loess Plateau. The differences in the sediment interception efficiency among the check dams in the watershed were analyzed according to field observations at 17 check dams. The results show that the average erosion intensity under the “7–26” extreme rainstorm was approximately 2.03 × 10⁴ t/km², which was 5 times that in the second largest erosive rainfall in 2017 (4.15 × 10³ t/km²) and 11–384 times that for storms in 2018 (0.53 × 10² t/km² - 1.81 × 10³ t/km²). Under the “7–26” extreme rainstorm, the amount of soil erosion in the Chabagou watershed above the Caoping hydrological station was 4.20 × 10⁶ t. The sediment interception efficiency of the check dams with drainage canals (including the destroyed check dams) and with drainage culverts was 6.48 and 39.49%, respectively. The total actual sediment amount trapped by the check dams was 1.11 × 10⁶ t, accounting for 26.36% of the total amount of soil erosion. In contrast, 3.09 × 10⁶ t of sediment were input to the downstream channel, and the sediment deposition in the channel was 2.23 × 10⁶ t, accounting for 53.15% of the total amount of soil erosion. The amount of sediment transport at the hydrological station was 8.60 × 10⁵ t. The Sediment Delivery Ratio (SDR) under the “7·26” extreme rainstorm was 0.21. The results indicated that the amount of soil erosion was huge, and the sediment interception efficiency of the check dams was greatly reduced under extreme rainstorms. It is necessary to strengthen the management and construction technology standards of check dams to improve the sediment interception efficiency and flood safety in the watershed.  相似文献   

Mass flows and river response in rapid uplifting regions – A case of lower Yarlung Tsangpo basin,southeast Tibet,China   总被引：1，自引：0，他引：1  

《国际泥沙研究》2020,35(6):609-620

The fluvial geomorphology in tectonically active (particularly rapid uplift) regions often undergoes continuous change. The rapid uplift is coincident with high erosion rates; consequently, incised valleys are formed. Mass flows (for example, avalanches, landslides, and debris flows) in incised valleys can markedly influence fluvial processes and even reshape valley geomorphology. However, these processes and long-term evolution corresponding to mass flows require further clarification. Field campaigns were carried out in the region near the Yigong Tsangpo and Palong Tsangpo Rivers (hereafter the Yigong and Palong Rivers), the two largest tributaries of the lower Yarlung Tsangpo River, to examine the feedback between fluvial processes and mass flows. Remote sensing images from recent decades were used to compare the channel morphology before and after typical mass flows (particularly catastrophic ones). The morphology of the lower Yigong River has evidently been impacted by landslides, while that of the Palong River has mainly been shaped by glacial processes and debris flows. At present, the morphology of the latter consists of alternating sections of gorges and wide valleys, with a staircase-like longitudinal profile. The gorge sections exhibit single and deeply incised channels with a high-gradient channel bed and terraces. In contrast, the wide valley sections consist of lakes, braided or anabranching channels, gentle bed gradients, and thick alluvial deposits. Debris flows occur more frequently in gullies in the reaches of the gorge sections and rarely in gullies along the wide valley sections. The occurrence of mass flow events has resulted in an imbalance of the previous (quasi-)equilibrium in the river morphology; however, this has triggered negative feedback that is driving the transient river morphology to a new state of (quasi-)equilibrium.  相似文献   

Geo-engineering properties of expansive soil treated with xanthan gum biopolymer     

Suresh Prasad Singh  Ritesh Das 《Geomechanics and Geoengineering》2020,15(2):107-122

ABSTRACT

This paper presents the effectiveness of xanthan gum (XG) biopolymer in stabilising the expansive soil. The XG biopolymer is mixed with expansive soil in different proportions such as 0%, 0.2%, 0.5%, 0.8% and 1.0% by weight of the dry soil mass. The plasticity, compaction, swelling, compressibility, hydraulic conductivity, strength and durability characteristics of the treated and un-treated expansive soil are examined. Results show that the plasticity index of the treated soil mass initially increases but beyond 0.5% biopolymer addition it decreases sharply. The optimum moisture content and maximum dry density of treated soil, found out from light and heavy compaction tests, do not follow any definite trend. It is also found that increasing XG content increases compressibility slightly but, it reduces swelling pressure, differential free swelling value and hydraulic conductivity remarkably. On the other hand, time-dependent compressive strength and resistance to mass loss increases with increasing XG content. Microscopic examination confirms the formation of gel-like linkage, which brings about the modifications in the treated expansive soil.  相似文献