Monitoring baseline suspended sediment in forested basins: the effects of sampling on suspended sediment rating curves

Abstract

Rating curves are widely used for directly assessing changes in the suspended sediment delivery process and indirectly for estimating total yields. Four sampling methods were simulated over a 31-day record of suspended sediment from the North Fork of the Mad River near Korbel, California. The position and size of the four groups of plotted slope/intercept pairs indicated differences in bias and variance among the methods. Estimates of total yield for the 31-day period and for storms of three sizes were also biased according to sampling method. A standard bias-correcting technique improved yield estimates, but did not remove sampling bias uniformly. Methods of data collection have a large and systematic effect on the estimation of rating-curve parameters and on estimates of suspended sediment yield. Differences attributed to land management may, in fact, result from changes in sampling methods.     

Interannual variation of suspended sediment load and sediment yield in an alpine catchment

Abstract

The results are described of 16 years operation of a measuring station for the automatic recording of water discharge, bed load and suspended sediment transport in the Rio Cordon catchment, a small alpine basin (5 km²) located in northeastern Italy. Hillslope erosion processes were investigated by surveying individual sediment sources repeatedly. Annual and seasonal variations of suspended sediment load during the period 1986–2001 are analysed along with their contribution to the total sediment yield. The results show that suspended load accounted for 76% of total load and that most of the suspended sediment transport occurred during two flood events: an extreme summer flash flood in September 1994 (27% of the 16-years total suspended load) and a snowmelt-induced event in May 2001 accompanied by a mud flow which fed the stream with sediments. The role of active sediment source areas is discussed in relation to the changes in flood peak—suspended load trends which became apparent after both the 1994 and the 2001 events.     

Temporal variation in suspended sediment transport: linking sediment sources and hydro-meteorological drivers

Suspended sediment concentrations (SSCs) in rivers are variable in time due to interacting soil erosion and sediment transport processes. While many hydro-meteorological variables are correlated to SSCs, interpretation of these correlations in terms of driving processes requires in-depth knowledge of the catchment. Detailed sediment source information is needed to establish the causal linkages between driving processes and variations in SSC. This study innovatively combined sediment fingerprinting with multivariate statistical analyses of hydro-meteorological data to investigate how differential contributions of sediment sources control SSC in response to hydro-meteorological variables during high-flow events in rivers. Applied to the River Aire (UK), five sediment sources were classified: grassland topsoil in three lithological areas (limestone, millstone grit and coal measures), eroding riverbanks, and street dust. A total of 159 suspended sediment samples were collected during 14 high-flow events (2015–2017). Results show substantial variation in sediment sources during high-flow events. Limestone grassland and street dust, the dominant contributors to the suspended sediment, show temporal variations consistent with variations in total SSC, and are correlated with precipitation and discharge shortly prior and during high-flow events (i.e. fast mobilization to and within river). Contrarily, contributions from millstone and coals grassland appear to be driven by antecedent hydro-meteorological conditions (i.e. lag-time between soil erosion and sediment delivery). Riverbank material is poorly correlated to hydro-meteorological variables, possibly due to weak source discrimination or the infrequent nature of its delivery to the channel. Differences in source-specific drivers and process interactions for sediment transport demonstrate the difficulty in generalizing sediment transport patterns and developing targeted suspended sediment management strategies. While more research is essential to address different uncertainties emerging from the approach, the study demonstrates how empirical data on sediment monitoring, fingerprinting, and hydro-meteorology can be combined and analysed to better understand sediment connectivity and the factors controlling SSC. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.     

Retrieval of suspended sediment concentrations in large turbid rivers using Landsat ETM+: an example from the Yangtze River,China

Suspended sediment concentration (SSC) is a critical parameter in the study of river sediment transport and water quality variation, but traditional measurement methods are costly and time‐consuming. This paper is focused on presenting a methodology that may be useful in estimating SSC which is of key importance in process geomorphology and hydrology. In previous studies, remote sensing has been applied to estimate the SSC of sea waters as well as low turbid inland waters like lakes, reservoirs and short river reaches visible within a single Landsat satellite image coverage. Rivers, especially highly turbid large rivers, have largely been ignored. The dataset used in this paper includes measured SSC and multi‐temporal Landsat ETM+ images covering most part of the Yangtze River. Using an effective easy‐to‐use atmospheric correction method that does not require in situ atmospheric conditions, retrieved water reflectance of Band 4 was found to be a good SSC indicator within the large SSC range 22–2610 mg l^–1. The newly developed regression relation between SSC and water reflectance of Band 4 appears to be able to provide a relatively accurate SSC estimate directly from Landsat ETM+ images for the Yangtze River from the upper, the middle to the lower reaches. With the relation it is possible to estimate or map out SSC dynamics of large rivers which lack SSC data due to constraints of conventional measurements. Copyright © 2009 John Wiley & Sons, Ltd.     

利用重复地震研究滦县地区的地壳介质变化

运用双差定位法,对滦县地区2002年1月至2010年8月ML≥2.0地震进行精定位,利用射线追踪方法,对滦县地区的重复地震进行位置归一处理,计算滦县地区重复地震序列经过射线追踪方法校正后得到的P波走时差变化.研究发现,2010年3月6日滦县ML4.7地震前糙甸地震台、兴隆东地震台、蓟县地震台和遵化地震台记录到P波走时差...     

基于时间序列MODIS影像的鄱阳湖丰水期悬浮泥沙浓度反演及变化

悬浮泥沙浓度是描述水质的重要参数之一,获得其在空间和时间上的分布信息对于理解、管理和保护湖泊生态系统是必要的.此研究旨在建立基于中分辨率成像光谱仪(MODIS)影像的鄱阳湖悬浮泥沙浓度反演模型,并利用建立的模型反演2000-2007年鄱阳湖丰水期的悬浮泥沙浓度,分析其在时间和空间上的变化特征并对引起这些变化的原因进行讨论.研究结果揭示:MODIS Terra影像红波段与悬浮泥沙浓度具有显著的相关性(R2=0.92,s.e.=12.02mg/L,F=154.30,P<0.001),可以用于鄱阳湖丰水期悬浮泥沙浓度的反演;自2000-2007年间,鄱阳湖悬浮泥沙浓度呈明显的时间和空间分布特征,在南部水体悬浮泥沙浓度无明显变化,在北部呈增加趋势,而中部水体泥沙浓度波动较大;鄱阳湖北部的采砂活动是导致此区域悬浮泥沙浓度增加的主要原因,其与长江江水倒灌鄱阳湖共同作用引起鄱阳湖中部泥沙浓度的波动,抚河、信江和饶河输沙量的非显著变化也导致南部鄱阳湖水体悬浮泥沙浓度的非显著变化.     

Temporal variation of suspended sediment load in the Pearl River due to human activities

Data on sediment flux at three hydrologic stations from the 1950s to 2006 are utilized to study the decadal,annual,and monthly variations in suspended sediment load delivered from the Pearl River to the ocean.Results show that variations in sediment flux from three main tributaries,including the West River,the North River and the East River,are spatially non-uniform.Since nearly 90%of the suspended sediment load comes from the West River,its variation has dominated the overall tendency of sediment flux in the entire Pearl River.Although a significant decreasing trend exists in the annual variation of the total sediment flux,the decadal change can be divided into an increasing phase and a decreasing phase,with the turning point between the two phases in the late 1980s.From the 1950s to the 1980s,the average annual river sediment flux increased by 30.43%.However,sediment flux has decreased significantly since the 1990s,with the average sediment flux being 38.60%less in the 2000s than that in the 1950s.The current sediment flux is also 52.93%less than its peak in the 1980s. The monthly variation pattern of the suspended sediment load transport to the sea is more interesting. For the West River,all months show a decreasing trend,and for most months the reduction values are significant.However,for the East River the sediment load shows a decrease trend in the dry season and an increase trend in the wet season.The method of regression analysis was used to study the influence of precipitation in the variation on the sediment flux.It was found that the climate change is not the main driving force behind the variation in suspended sediment load.Before the 1990s, intensive land use destroyed the vulnerable ecosystem of the upper Pearl River,and speeded up the process of rocky desertification.Consequently,aggravated soil erosion caused an increase in suspended sediment load.However,sediment retention within reservoirs had begun to play a dominant role after the massive construction of large dams after 1990,and resulted in a decrease in the suspended sediment load delivered to the ocean.     

Investigating suspended particulate matter in coastal waters using the fractal theory

Ocean Dynamics - Suspended particulate matters (SPM) in coastal waters were investigated with an approach combining suspended particulate matter concentrations (SPMCs) measured by an optical...     

Seasonal and spatial distribution of nonylphenol and IBP in Saemangeum Bay, Korea

In order to investigate spatial and temporal distribution of organic pollutants in the Saemangeum Bay, organophosphorus pesticides (10), alkylphenols (8), chlorophenols (2), bisphenol A were analyzed from the surface seawater taken in 2002–2003. Most of the analytes were not detected in all stations except nonylphenol and S-benzyl-O,O-di-isopropyl phosphorothioate (IBP). Concentrations of nonylphenol and IBP ranged from ND to 298 ng/l and from ND to 1840 ng/l, respectively. The high levels of nonylphenol and IBP were found in the estuary areas of Mangyeong and Dongjin River. The levels of nonylphenol and IBP in surface seawater varied through seasons and the high levels of nonylphenol and IBP were in summer season (August). Based on real time monitoring of IBP and on correlation between concentrations of target compounds and contents of salinity in seawater, physical mixing and diffusion of seawater were found to be the major factors that affect the spatial distribution of IBP and nonylphenol in the Saemangeum Bay environment.     

Phosphorus fractionation and release characteristics of sediment in the Saemangeum Reservoir for seasonal change

Periodical algal blooms result in deposition and release of phosphorus (P) from the sediment into the water. Therefore, during seasonal changes when algal particles begin to settle to the bottom, understanding the behavior and distribution characteristics of the P in sediment is the most important key to manage the water quality of the Saemangeum Reservoir. In this study, the variation of water quality and sediment composition including chlorophyll-a (Chl-a) and P was investigated to determine the interaction between water and sediment. The study focused primarily on algal particle sedimentation that affects the P release and mineralization of sediment. The Chl-a concentration in water showed a sharp decline in October when the algae began to die in the fall, and afterward the concentration of chemical oxygen demand (COD) and total P (TP) in the sediment increased due to the sedimentation of decaying algal particles in November. During the same period of time, the readily bio-available P (RAP) in the sediment showed a drastic increase in the upper region where the Chl-a concentration of water was high. In sequence, the high RAP zone shifted from the upper region to the lower region in the early winter. The RAP shift was considered to be derived from the physical flow of the overlying water from which the decomposing algae settled on the surface of the sediment. The Saemangeum Reservoir was constructed recently; therefore, all the types of inorganic P fractions except soluble reactive phosphorus (SRP) that exist on the bottom surface of the lake and the marsh's sediment layer were not sufficient to significantly influence the overlying water. On the other hand, the released P from the algae was distinct and sensitive to the seasonal change. In conclusion, the algal particle sedimentation was important to control eutrophication rather than P release from the mineralized inorganic P of the sediment surface layer in the Seamangeum Reservoir.     

Impacts of marine debris on wild animals in the coastal area of Korea

Over the last decade, marine debris has become a major factor affecting the coastal ecosystem of Korea. This study compiled information regarding how marine debris impacts wildlife in Korea. Cases of marine debris impacting wildlife were collected from experts of various fields and from local participants through an open access website from February 2010 to March 2012. A total of 21 species were affected by marine debris: 18 species of birds, 2 species of mammals, and 1 species of crustacean. Five threatened or protected species were identified: black-faced spoonbill, finless porpoise, water deer, whooper swan, and greater painted snipe. Recreational fishing gears were the types of debris that most frequently impacted wildlife, especially birds. Black tailed gulls were the most vulnerable species to recreational fishing hooks and lines. Although it was preliminary, this study revealed that recreational fishing activities should be prioritized when managing marine debris in Korea.     

Modelling changes in suspended sediment from forest road surfaces in a coastal watershed of British Columbia

Erosion from logging road surfaces, cut slopes, banks, and ditches represents a chronic source of sediment input to streams that can degrade aquatic habitats. Road surface erosion is of particular concern because the magnitude of sediment generation when traffic levels are high can be large. Current models for predicting sediment production from roads require information on area‐specific sediment delivery, which is not often available. Here, we developed a model to quantify suspended sediment concentrations (SSC) generated by forest roads surfaces under different conditions of use and density. This model is designed for a typical medium‐size coastal watershed of British Columbia or the American Pacific Northwest, and was applied to the Chilliwack River watershed as a case study. The results illustrate that intensive use of forest roads combined with high road density can increase the number of extreme sedimentation events over a predetermined threshold. A comparison of the effects of road density and the level of road use suggests that the level of road use is more important than the road density for the generation of fine sediment from road surfaces. However, the model omits the impact of roads on mass movements in a watershed, which represent a major source of sediment in steep watersheds, so the effect of road density is likely more substantial than the model predicts. The model is an attempt to overcome field data limitations by using an empirical relation between SSC and traffic variables, and presents a starting point for more intensive field studies that could be used to validate it. Copyright © 2013 John Wiley & Sons, Ltd.     

Temporal variation of suspended sediment transport in the Koga catchment,North Western Ethiopia and environmental implications

Event sediment transport and yield were studied for 45 events in the upstream part of the 260 km² agricultural Koga catchment that drains to an irrigation reservoir. Discharge and turbidity data were collected over a period of more than a year, accompanied by grab sampling. Turbidity was very well correlated with the sediment concentrations from the samples (r = 0.99), which allowed us to estimate the temporal patterns of sediment concentrations within events. The hysteresis patterns between discharge and sediment concentrations were analysed to provide insight into the different sediment sources. Anticlockwise patterns are the dominant hysteresis patterns in the area, suggesting smaller contributions of suspended sediment from the river channels than from the hillslopes and agricultural areas. Complicated types of hysteresis patterns were mostly observed for long events with multiple peaks. For a given discharge, sediment yields in August and September, when the catchment was almost completely covered with vegetation, were much smaller than during the rest of the rainy season. The hysteresis patterns and timing suggest that the sediment availability from the agricultural areas and hillslopes affects sediment yields more strongly than does peak discharge. Two distinct types of sediment rating curves were observed for the season when the agricultural land was covered with vegetation and when it was not, indicating the dominating contribution of land use/cover to sediment yields in the catchment. The rate of suspended sediment transport in the area was estimated as 25.6 t year^?1 ha^?1. Copyright © 2013 John Wiley & Sons, Ltd.     

利用重复地震观测重庆巫山地区地壳介质变化

利用波形互相关技术,对重庆数字地震台网记录的巫山地区90次地震波形资料进行相关计算,识别出24对同时被2个地震台站记录且各台波形互相关系数不小于0.8的重复地震对;利用射线追踪方法,对巫山地区重复地震位置做归一化处理,得到所选台站记录地震P波走时差变化,结果显示,在2013年重庆巫山M_L 3.7地震前,建坪、双龙、荆竹地震台记录到该地区短期地壳介质速度有明显升高现象。     

Evaluating spatial variation of suspended sediment rating curves in the middle Yellow River basin,China

Abstract The suspended sediment load in the middle Yellow River basin (YRB) cannot be well predicted by capacity‐based transport formulas because a large fraction of suspended sediment load is composed of wash load. This study evaluated the spatial variations of sediment rating curves (SRCs) in the middle YRB. Both power and linear SRCs were used to fit daily flow and suspended sediment concentration (SSC) historical data at 49 gauging stations throughout the middle YRB. The spatial variation in regression coefficients was investigated, and the relationship between regression coefficients and the physical characteristics of watersheds was discussed. The results indicate that SRC regression coefficients vary with drainage area and basin slope, but their responses to these parameters are remarkably different in watersheds with different underlying surfaces, which indicates the significance of sediment availability, erodibility, and grain size distribution. For power SRCs representing sediment transport in unsaturated flows, the regression coefficients are more closely correlated with the drainage area in loess regions and with the basin slope in rock mountain regions. For linear SRCs representing sediment transport in saturated flows, saturated SSCs vary with coarse (particle size > 0.05 mm) and fine (particle size < 0.01 mm) fractions in suspended sediment. The maximum saturated SSC among the different gauging stations is associated with the optimal grain size composition of suspended sediment, which has been proposed for loess regions in previous studies. This study provides theoretical support for estimating the regression parameters for sediment transport modelling, especially in ungauged basins.     

Determination of vertical displacements over the coastal area of Korea due to the ocean tide loading using GPS observations

This paper describes the GPS applicability for detecting the vertical displacements of ground stations caused by ocean tide loading effects. An experiment was carried out using 12 permanent GPS stations located in the coastal area of Korea using data in the period 1 July until 26 August 2003. The relative height differences were calculated from hourly DGPS data processing based on the carrier-phase observation. The power spectra of the M₂ and N₂ constituents of ocean tide loading were derived using the CLEAN algorithm. The differential vertical displacements generated by the ocean tide loading effect are typically 3–25 mm in coastal area of the Korea. We compared the results from GPS with those of the ocean tide models, NAO.99Jb regional model and GOT00.2, FES99 global models. The M₂ (N₂) amplitude differences of vertical displacements between GPS and GOT00.2 is 1.22 ± 3.61 mm (1.01 ± 1.48 mm), and that of the M₂ (N₂) amplitude difference between GPS and FES99 is 0.04 ± 4.64 mm (0.64 ± 1.75 mm), whereas the M₂ (N₂) amplitude difference between GPS and NAO.99Jb are 0.05 ± 1.03 mm (0.86 ± 1.18 mm). The highest vertical displacements at the PALM station are found for 24.5 ± 0.7 mm from GPS observation, and 22.9 mm from the regional model NAO.99Jb and 13.17 and 10.00 mm from the global models GOT00.2 and FES99, respectively. These values show that the vertical displacements derived from GPS are in good agreement with those of the regional model NAO.99Jb around Korea, more than with the global models. This result indicated that GPS is an effective tool to measure the vertical displacement caused by the ocean tide loading effect in the coastal area, and we need to use the NAO.99Jb ocean tide model rather than the global ocean tide models in and around the Korean peninsula for position determination with permanent GPS installations. This work demonstrates that vertical displacement caused by the M₂ and N₂ constituents of ocean tide loading can be measured by carrier-phase DGPS.     

利用重复地震观测粤闽交界地区地壳介质变化

利用粤闽两省数字化地震台网2007年6月～2010年5月的走时及波形记录对南澳地区ML≥1地震用双差法重新进行定位,根据定位结果挑选重复地震丛,并研究地震丛的P波走时经伪弯曲射线追踪技术及波形互相关校正后的走时差变化.经上述处理后,汕头台、潮州台记录的南澳地区地震的P波走时差在2008年6～8月间出现负异常,经与地震活动性及形变观测资料对比分析,认为该时段的负异常反映了区域地壳介质速度有所上升.     

利用重复地震观测重庆武隆地区地壳介质变化

选取重庆数字地震台网记录的武隆地区107次M_L≥1.5地震波形和观测报告资料,采用波形互相关技术进行相关计算,识别出12组同时被3个地震台站记录且各台波形互相关系数不小于0.8的重复地震。利用射线追踪方法,对武隆地区重复地震位置做归一化处理,得到所选台站记录地震P波走时差变化,结果显示:在2017年武隆M_S5.0地震前4年,武隆、仙女山、涪陵地震台记录到P波走时差均存在长期的负异常变化,持续时间长达339天,共出现18次负值,表明该时段地壳介质速度有明显升高现象。