Landsat Image-Based Spatiotemporal Variation Analysis of Erosion and Deposition off the Qingshuigou of the Yellow River Delta from 1984 to 2021

Owing to climate change and human activity,the Qingshuigou of the Yellow River Delta(YRD)has undergone dynamic changes in erosion and deposition.Therefore,studying these changes is important to ensure ecological protection and sustainable development.In this study,the trend of erosion-deposition evolution in the Qingshuigou was investigated based on 38 coastline phases extracted from Landsat series images of the YRD at one-year intervals from 1984 to 2021.The periodicity of the scouring and deposition evolution was also analyzed using wavelet analysis.Results showed that the total area of the Qingshuigou was affected by deposition and erosion and that the fluctuation first increased and then decreased.The total area reached a maximum in 1993.The depositional area first increased and then decreased,whereas the overall erosion area decreased.Deposition and erosion areas showed periodic changes to some extent;however,the periodic signal intensity decreased.Furthermore,factors including channel morphological evolution and variations in water and sediment discharge affect the spatiotemporal dynamics of erosion and deposition processes.The application of nonconsistency tests finally revealed that deposition area and flushing magnitude exhibited non-stationarities,which are potentially attributed to impacts from climatic change drivers.

The analysis on reservoir sediment deposition and downstream river channel scouring after impoundment and operation of TGP

According to the measured data after impoundment and operation of the Three Gorges Reservoir,the reservoir sediment deposition and downstream river channel scouring are described briefly and compared with the research results achieved in the demonstration stage.It is indicated through analysis that the reservoir sediment deposition and downstream river channel scouring during 8-year impoundment and operation are still within the original forecast,so the original forecasting results are feasible.The further observation and comparison should be conducted because the comparison between the observed data and the original forecast is not so sufficient in time and the prototype observation and related research work should be strengthened in the future.

Impact of soil texture and sweetpotato cropping system on soil erosion and nutrient loss in the Three Gorges Reservoir Area of the Changjiang River

This study investigated the impact of soil texture and sweetpotato cropping system on soil erosion and nutrient loss in the drought infield of the Three Gorges Reservoir Area of Changjiang River under field conditions. A factorial experiment was conducted in the study using five soil textures and two cropping systems. The lost soil during the crop season was recovered by a soil-blocking device and the dry weights for the total lost soil and its nutrient components, such as ammonium nitrogen, effective phosphorus, K^＋ and organic matter were analyzed. We found that soil texture significantly affected the dry weights of the total lost soil, effective phosphorus, K^＋, and organic matter, while sweetpotato cropping systems and interaction between soil texture and sweetpotato cropping system affected the dry weights of the total lost soil, the effective phosphorus and organic matter. Among the five soil textures tested, Da and Huang caused significantly less soil erosion and nutrient loss compared with the other three soil textures; intercropping sweetpotato with corn significantly reduced soil erosion and nutrient loss.

Numerical evaluation of the effects of the Dongzhuang reservoir on channel deposition in the Lower Wei River in China

Jing River is a tributary of the Wei River which is the largest tributary of the Yellow River. Sediments eroded from the upland of the Jing River basin are one of the major contributors of sediment entering the lower Wei River(LWR). The Dongzhuang reservoir is designed to be constructed on the lower Jing River for flood control and water resources regulation, and this may change the sustainable management of the LWR as changed channel deposition by trapping sediments and releasing concentration-limited flow. Its effects on the LWR, especially the deposition distribution, should be analyzed. The steady quasi-two-dimensional dynamic model was adopted to estimate the deposition processes in the LWR. Then, the qualitative effects of the Dongzhuang reservoir on channel deposition were evaluated and compared with historical data, including capacity loss in other reservoirs and measured deposition in the LWR. Analyses indicated that the annual deposition in the LWR will decrease by approximately two-thirds due to the reservoir’s operation. After 15 years of operation, the effects of the Dongzhuang reservoir on the lower channel will decrease gradually. Moreover, its effects on lateral distribution in different sub-reaches are different. After the reservoir’s operation, the floodplain of the Xianyang–Lintong(XY-LT) sub-reach will change its sediment regime from deposition to erosion. For the Lintong–Huaxian(LT-HX) sub-reach, deposition in the main channel will be more serious during the first 30 years of operation. For the Huaxian–Tongguan (HX-TG) sub-reach, the reservoir will have almost no effects on the lateral distribution. All these analyses may benefit the sustainable management of the Wei River and the Yellow River.

Dated deposition couplets link catchment erosion flux with storm discharge on the Chinese Loess Plateau

Tracing erosion flux within a single catchment is one of the major targets for the Earth's Critical Zone science. The sedimentary succession in landslide-dammed reservoirs within the Chinese Loess Plateau(CLP) serves as a valuable archive of past erosion history. Deposition couplets and annual freeze–thaw layers were firstly identified for the sedimentary succession of the Jingbian reservoir on the northern CLP with high-resolution XRF core scanning. The deposition couplets in the reservoir since 1963 A.D. were further dated with ^(137) Cs activity. We found consistent one-to-one correspondence between couplet specific sediment yield and storm intensity. The reconstructed soil erosion history highlights the control of storm intensity and frequency on loess erosion on the northern CLP in the past hundreds of years.

Using ^(137)Cs Tracing Methods to Estimate Soil Redistribution Rates and to Construct a Sediment Budget for a Small Agricultural Catchment in the Three Gorges Reservoir Region,China

Soil erosion and associated off-site sedimentation are threatening the sustainable use of the Three Gorges Dam. To initiate management intervention to reduce sediment yields, there is an increasing need for reliable information on soil erosion in the Three Gorges Reservoir Region （TGRR）. The purpose of this study is to use 137Cs tracing methods to construct a sediment budget for a small agricultural catchment in the TGRR. Cores were taken from a pond and from paddy fields, for laTCs measurements. The results show that the average sedimentation rate in the pond since 1963 is 1.50 g cm-2 yr-1 and the corresponding amount of sediment deposited is 1,553 t. The surface erosion rate for the sloping cultivated lands and the sedimentation rate in the paddy fields were estimated to be 3,770 t km-2 yr-1 and 2,600 t km-2 yr^1 respectively. Based on the estimated erosion and deposition rates, and the area of each unit, the post 197o sediment budget for the catchment has been constructed. A sediment delivery ratio of 0.5 has been estimated for the past 42 years. The data indicate that the sloping cultivated lands are the primary sediment source areas, and that the paddy fields are deposition zones. The typical land use pattern （with the upper parts characterized by sloping cultivated land and the lower parts by paddy fields） plays an important role in reducing sediment yield from agricultural catchments in the TGRR. A 137Cs profile for the sediment deposited in a pond is shownto provide an effective means of estimating the land surface erosion rate in the upstream catchment.

RS-GIS Based Assessment of River Dynamics of Brahmaputra River in India

The Brahmaputra River is one of the largest alluvial rivers in the world characterized by frequent bank erosion leading to channel pattern changes and shifting of bank line. This study is aimed at quantifying the actual bank erosion/deposi- tion along the Brahmaputra River within India for a period of eighteen years (1990-2008). The entire course of Brah- maputra River in Assam from upstream of Dibrugarh up to the town Dhubri near Bangladesh border for a stretch of around 620 kms has been studied using an integrated approach of Remote Sensing and Geographical Information Sys- tem (GIS). The channel configuration of the Brahmaputra River has been mapped for the years 1990 and 2008 using IRS 1A LISS-I, and IRS-P6 LISS-III satellite images respectively. The analysis of satellite data has provided not only the information on the channel configuration of the river system on repetitive basis but also has brought out several sig- nificant facts about the changes in river morphology, stable and unstable reaches of the river banks and changes in the main channel. The results provide latest and reliable information on the dynamic fluvio-geomorphology of the Brah- maputra River for designing and implementation of drainage development programmes and erosion control schemes in the north eastern region of the country.

PROBLEMS OF RESERVOIR SEDIMENTATION IN CHINA

As there are many heavily sedimentladen rivers in China, with high sediment concentration and a large quantity of sediment load, the sedimentation problems of the reservoirs built on those rivers are so serious that the amount of sediment deposited in the reservoirs is great and the rate of sedimentation is accelerated. According to the statistics, up to the end of 1981, a total amount of 11.5×109m3 of sediment were accumulated in those reservoirs, i.e. 14.2% of the total designed capacity were lost. The average annual loss in storage capacity reached 2.3 percent, being the highest in the world. Silting of impounding lakes not only has an effect on the benefits of the reservoirs and seriously threatens the life of reservoirs, but also results in many environmental problems which were not fully estimated in the planning of the reservoirs. In this paper, the situation of reservoir deposition in China are described from the following aspects: 1) the characteristics of hydrology and sediment of the rivers; 2) the seriousness of reservoir sedimentation in China; 3) problems caused by reservoir deposition; 4) the methods of minimizing sediment deposition, etc.

小浪底水库运行以来对黄河下游河道河床演变特性的影响

小浪底水库自1999年10月下闸蓄水,23年来深刻改变了进入黄河下游河道的径流泥沙过程,进而引起了下游河道的再造床。本研究以1960—2022年长序列水文泥沙、断面地形、遥感影像等多源资料为基础,从径流泥沙、冲淤演变、形态调整三个方面阐明了小浪底水库运行以来对下游河道河床演变特性的影响。结果表明:(1)水库拦沙效果显著,下泄水量在年内分配更加均匀、沙量则向汛期更加集中;大流量和高含沙事件的严重程度和发生频率均有所降低;悬沙调整不明显,床沙粗化显著。(2)扭转了黄河下游河道持续淤积的趋势,冲淤调整主要发生在花园口至高村的游荡性河段;冲刷效率持续下降,主槽过流能力得到显著恢复。(3)游荡性河段横断面形态向窄深发展,二级悬河发育得到有效缓解,整体河势处于相对稳定状态。研究成果丰富了多沙河流修建水库对下游河道影响的科学认识,也可为小浪底水库优化调度提供科技支撑。

Integration of colour bathymetry, LiDAR and dGPS surveys for assessing fluvial changes after flood events in the Tagliamento River (Italy)

The estimation of underwater features of channel bed surfaces without the use of bathymetric sensors results in very high levels of uncertainty. A revised approach enabling an automatic extraction of the wet areas to create more accurate and detailed Digital Terrain Models (DTMs) is here presented. LiDAR-derived elevations of dry surfaces, water depths of wetted areas derived from aerial photos and a predictive depth-colour relationship were adopted. This methodology was applied at two different reaches of a northeastern Italian gravel-bed river (Tagliamento) before and after two flood events occurred in November and December 2010. In-channel dGPS survey points were performed taking different depth levels and different colour scales of the river bed. More than 10,473 control points were acquired, 1107 in 2010 and 9366 in 2011 respectively. A regression model that calculates channel depths using the correct intensity of three colour bands (RGB) was implemented. LiDAR and water depth points were merged and interpolated into DTMs which features an average error, for the wet areas, of ±14 cm. The different number of calibration points obtained for 2010 and 2011 showed that the bathymetric error is also sensitive to the number of acquired calibration points. The morphological evolution calculated through a difference of DTMs shows a prevalence of deposition and erosion areas into the wet areas.

三门峡水库控制运用方式的优化探讨

三门峡水库“蓄清排浑”运用为多沙河流的治理提供了宝贵经验,随着来水来沙情况的变化及对水库功能需求和对水库泥沙冲淤规律认识的深化,该运行方式亦在实践中不断调整和完善。为此,针对不同的典型年份设定集中敞泄与分段敞泄的敞泄排沙方案,采用一维非恒定水沙数学模型,对选取的2018~2019年丰水少沙年和2014~2016年枯水少沙年设定12种控制运用方案进行模拟,比较各方案下库区冲淤变化的优劣,据此选取适合三门峡水库的控制运用方式。结果表明,2018~2019年分段敞泄方案的冲刷效果优于集中敞泄方案,即使在后汛期的控制水位抬高至310 m,也能达到较好的冲刷效果;2014~2016年分段敞泄方案虽优于集中敞泄方案,但其冲刷主要集中于2014年汛期,2015、2016年整体呈淤积状态,综合考虑建议枯水少沙年份水库采用“泥沙年际调节”运用模式。

黑龙江干流黑河市城区段河床演变研究

黑龙江黑河市城区河段河道受自然及人为因素影响,河床演变复杂。采用Mann-Kendall趋势检验法和双累积曲线法分析了水沙变化趋势。基于实测水文和泥沙资料,对河床稳定性及冲淤变化进行了定量研究。研究结果表明,该河段属于少沙河流,结雅河口以上年径流和输沙量随时间呈减小趋势,结雅河口以下年径流没有明显的趋势性变化,年输沙量呈减小趋势。自然状态下,河段岸线和深泓线位置基本稳定,河床冲淤变化不大,以约10年为一个周期,基本可以达到冲淤平衡。在人类活动及支流汇入影响下,黑河水位站至长发岛段纵向不稳定,预测会引起该段未防护岛屿洲滩的岸线变迁。

基于径流侵蚀功率的长江典型流域能沙关系模型及改进

基于径流侵蚀功率概念建立流域能沙关系模型,可为长江流域泥沙变化精准模拟与水土保持规划提供技术支撑。该研究以长江典型流域及其典型小流域为研究对象,通过收集1965—2018年金沙江流域、嘉陵江流域和湘江流域3个典型流域逐日水沙数据以及万安和李子口2个典型小流域2014—2020年场次降水径流泥沙数据,采用径流侵蚀功率、径流量和降雨侵蚀力对比分析不同时空尺度水沙(径流量和输沙量)、雨沙(降雨侵蚀力和输沙量)和能沙(径流侵蚀功率和输沙量)关系的优劣性,解析能沙关系优越性,并识别能沙关系非一致性变化,从而改进能沙关系模型提高流域输沙量模拟精度。结果表明:1)长江流域3个典型流域及2个典型小流域,在绝大部分情况下能沙关系的表现总是优于水沙关系和雨沙关系,在场次、月和年尺度修正的决定系数最大值分别可达到0.94、0.87和0.54。2)对于不同时间尺度,其流量序列中任意2个流量乘积与输沙量的相关性较高时,第一个流量Q_(1)分位点总是接近1且第二个流量Q_(2)分位点在0.5附近或者高于0.5。基于径流侵蚀功率可以较为准确地计算不同时空尺度流域输沙量,具有明显适用性。3)随着时间升尺度,水沙、雨沙和能沙关系逐渐变差,3个典型流域径流侵蚀功率和输沙量在一些月份上均存在显著变化趋势和显著突变点(P<0.05)。特别是在年尺度上,输沙量均为显著减少趋势(P<0.05),其能沙关系均表现出非一致性变化。4)水库建设和植被增加是导致流域能沙关系变差的重要原因,其均与输沙量呈现极显著负相关(P<0.001)。通过考虑水库指数和NDVI改进能沙关系模型的年决定系数(R^(2))可提高27.28%~97.62%。研究成果可支撑开发新的流域泥沙预报模型,服务长江流域生态保护与高质量发展。

黄河下游河道冲淤分布模式及冲淤特征

为揭示黄河下游河道的沿程冲淤分布模式及分布特征,对黄河下游1952—2021年间共70年的河段实测冲淤量数据进行了系列统计分析。研究表明:(1)黄河下游河道存在7种沿程冲淤分布模式,其中全线冲刷、全线淤积、上冲下淤、上淤下冲等4种为基本模式。上淤下冲模式的冲淤临界位置在孙口附近,上冲下淤模式的冲淤临界位置在游荡性河段。各模式对河道整体冲淤的贡献率存在较大差异,两边冲中间淤模式对冲刷量的贡献率最大,全线淤积模式对淤积量的贡献率最大;(2)1952年以来,黄河下游河道沿程冲淤分布模式的变化过程可分为1952—1959年、1960—1985年、1986—1999年、2000年后共4个阶段;(3)各河段冲淤量大小以0点为中心近似呈偏态分布,冲淤量在多年尺度下具有沿程减小的趋势性特征以及“冲久必淤、淤久必冲”的周期性特征;(4)各河段整体冲淤发生年数差别不大,反映了河道冲淤的平衡趋向性;70年内淤积于黄河下游河床底部的泥沙有一半左右被冲走,花园口到孙口河段的累计冲淤量接近下游总冲淤量的8成,孙口以下河段很小;(5)全线冲刷模式为小浪底水库运用后下游河道的主要冲淤模式,小花段前期淤积的泥沙基本被冲完,夹高段、高孙段及孙艾段仅冲走了前期淤积泥沙的二到三成。研究结果总结了黄河下游河道的沿程冲淤分布模式,分析了冲淤分布特征,有助于深化对下游河道冲淤现象的整体认识。

黄河下游高村-孙口段冲淤变化及影响因素定量分析

为探究黄河过渡段河道滩槽演变规律,采用实测水沙和大断面数据,分析近年来高孙段河床冲淤、水沙条件和河床形态的演变,以年和汛期为时间尺度,用灰色关联度分析河槽冲淤量与水沙条件及河床形态的关联程度。结果表明,近年来高孙段以冲刷为主,汛期是年内输沙的主要时期;高村断面来沙系数可以分为波动减小(2002~2017年)和快速增加(2018~2019年)两大阶段,而河床形态中水力半径和宽深比变化趋势完全相反,糙率存在增大趋势;高村断面的水沙条件及河床形态与高孙段河道冲淤具有较高的关联程度,河床形态比水沙条件具有更高的相关性。

黄河下游游荡河段高含沙洪水期输沙规律研究

黄河下游河床长期处于淤积抬升状态,其冲淤演变规律对于下游河道治理有着重要影响。因此,快速预测不同量级高含沙洪水各河段的冲淤量以及判断高含沙洪水期黄河下游游荡河段冲淤影响很有必要。根据1960—2021年54场高含沙洪水的实测水沙资料,分析高含沙洪水期黄河下游游荡河段下站输沙率与上站流量、含沙量、输沙率之间的相关关系并建立关系式,系统地研究高含沙洪水的输沙规律。结果表明,下站输沙率与上站输沙率存在极强的相关性,进一步按来沙系数分级得到高含沙洪水期的输沙率公式,能够很好地模拟冲淤过程,极大地提高了与实测水沙资料的贴合度。以小浪底水文站为黄河下游游荡河段的进口控制水文站,采用按来沙系数分级所求的输沙率关系式能够较准确推求花园口站、夹河滩站、高村站的输沙率,从而计算小浪底—花园口、花园口—夹河滩和夹河滩—高村河段的累计冲淤量。

2022年长江中下游干流河道输沙与冲淤变化特点

2022年长江流域遭遇了汛期反枯的极端水文气象条件,导致长江中下游的水位降至有实测资料记录以来的同期最低,该极端水文情势使长江中下游河道冲淤变化出现了新特征。基于详细实测水沙监测及固定断面资料,对2022年极端水文气象条件下长江中下游干流河道输沙的冲淤变化特点进行深入分析。结果表明:1—6月份长江中下游各测站输沙量有增有减,总体上输沙量保持相对稳定;7—12月份各测站输沙量均出现了大幅下降,宜昌至九江河段通过输沙量法计算得知冲刷的泥沙总量为2391万t,通过断面法计算得知湖口至江阴河段泥沙淤积量为4657万m^(3)(湖口至大通冲刷量为1211万m^(3),大通至江阴淤积量为5868万m^(3)),江阴以下河段冲刷量为6335万m^(3)。上游来流减少和长江口潮位的影响是造成湖口至江阴河段淤积的主要原因。研究结果可为进一步探索长江中下游河道冲淤变化规律、预测未来的冲淤趋势提供重要参考。

塔里木河干流阿拉尔河段冲淤变化研究

近年来,人类活动成为影响河道冲淤变化的主要因素,使得塔里木河干流呈现出新的冲淤演变格局。采用塔里木河干流阿拉尔站多年的水沙量资料,结合河势变化图,对1958—2017年阿拉尔河段特性、断面变化、同流量水位及水位流量关系进行变化分析,归纳塔里干流阿拉尔河段冲淤演变特性,对影响塔里木河干流冲淤演变的驱动因素进行分析。结果表明:(1)水沙关系。从1960—2017年阿拉尔水量呈减小趋势,减小数值为9.61亿m^(3),年际水沙变化幅度大且年内水沙分布不均,1960—1999年沙量较大集中,其他时间段较稳定。(2)河道特性。阿拉尔附近是游荡型河道,河床宽且浅,河心滩及沙洲多且河床冲淤不定。(3)阿拉尔断面总体表现为大水冲刷、小水淤积、长时段内冲淤变化不大。(4)2005—2009年该断面总体冲淤变化不大,2009—2010年该断面发生冲刷,2010—2017年该断面总体表现为淤积,结合阿拉尔断面套绘,2005年该断面主槽滩唇高程为10.1 m,平滩流量为1600 m^(3)/s, 2010年该断面主槽滩高程为9.93 m,平滩流量增至1750 m^(3)/s左右。

长江王家洲崩岸治理及护岸效果分析

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