River Sediment Load Research Articles

Suspended particulate matter estimates using optical and acoustic sensors: application in Nestos River plume (Thracian Sea, North Aegean Sea)

The present study investigates the use of combined methods of optical and acoustic sensors, in collaboration with direct in situ measurements, for the calibration and validation of a model transforming acoustic backscatter intensity series into suspended particulate matter (SPM) concentration datasets. The model follows previously elaborated techniques, placing particular attention to the parameterization of the acoustic absorption index as a function of water physical properties. Results were obtained from the annual deployment (during 2007-2008) of an upward-facing acoustic Doppler current profiler (ADCP) (307 kHz), equipped with a Wave Array, and an optical backscatter sensor (OBS), at the bottom of Thassos Passage near Nestos River plume (Thracian Sea, Northern Greece). The OBS was calibrated through linear regression, using 2007 and 2012 field sampling data, exhibiting an error of 13-14 % due to chlorophyll presence. The ADCP signal was calibrated through simultaneous measurements of backscatter intensity and turbidity profiles. Harmonic analysis on the model-produced SPM concentrations explained the tidal influence on their variability, especially during the summer. Empirical orthogonal functions analysis revealed the impact of waves and wave-induced currents on SPM variability. Finally, Nestos River sediment load was found uncorrelated to the SPM change in Thassos Passage, due to the dispersal and sediment deposition near the river mouth.

A numerical investigation of freshwater and sediment discharge variations of Poyang Lake catchment, China over the last 1000 years

The Poyang Lake catchment, an important sub-catchment of Changjiang, experienced ‘Little Ice Age’ (LIA) and accelerating intensity of human activities during the last 1000 years. As such, the area and time period serve as a perfect case to study the variations in water and sediment discharge under combined natural and anthropogenic impact. Simulation results of the model HydroTrend indicate that the annual average cumulative water discharge of the five rivers entering Poyang Lake over the last 1000 years is 103.65 ± 1.80 km3, and climate change is the dominating factor determining water discharge variations over time. Influenced by the LIA (AD 1451–1850), the total water discharge of the five rivers was reduced by 10%. Sediment load discharging into Poyang Lake by the five rivers was only 9.21 ± 0.43 Mt yr−1 between AD 1000 and 1700, when the anthropogenic impact on the landscape was still low. However, with the human activities accelerating during the past 300 years, the sediment load entering Poyang Lake underwent a drastic change. Because of intensified soil loss, the total sediment load entering Poyang Lake during AD 1800–1950 increased by 58.7%, compared with AD 1000–1700. After AD 1950, the sediment load variation is mainly reflected by the combined impact of dam emplacement and soil erosion. As sediment interception by dams continuously increased over time, the total sediment load entering Poyang Lake during AD 1990–2000 is only 60.9% of that of the highest riverine sediment flux during AD 1951–1980, which is almost equal to that of the lowest level during AD 1000–1700. The sediment load of many rivers in the world exhibited similar variation trends as that of Poyang Lake under combined impact of climate change and human activities. Better understanding the mechanisms of these variation trends is helpful to analyzing the formation and evolution of an estuary-shelf sedimentary system over the Holocene.

Comparison of estuarine sediment record with modelled rates of sediment supply from a western European catchment since 1500

Marine and estuarine sediment records reporting impacts of historical land use changes exist worldwide, but they are rarely supported by direct quantified evidence of changes in denudation rates on the related catchments. Here we implement a spatially-resolved RUSLE soil erosion model on the 10000 km2 Charente catchment (France), supplied with realistic scenarios of land-cover and climate changes since 1500, and compare the results to a 14C-dated estuarine sediment record. Despite approximations, the model correctly predicts present-day Charente river sediment load. Back-cast modelling suggests that the Charente catchment is an interesting case where the sediment supply did not change despite increase in soil erosion resulting from 18th-century deforestation because it was mitigated by drier climate during the same period. Silt-sand alternations evidenced in the sediment record were correlated with sub-decadal rainfall variability.

Joint isotopic mass balance: a novel approach to quantifying channel bed to channel margins sediment transfer during storm events

AbstractThe important role of floodplains and the broader riparian zone in providing temporary storage for a large fraction of the annual sediment load of rivers is well established, but this understanding is largely based on observations of the long‐term average behavior of the catchment. Here we combine measurements of the fallout radionuclides 7Be and 210Pb and the stable isotopes of hydrogen in water to quantify fine sediment mobilization and storage in a stream and its channel margins during individual intermediate‐sized storm events with recurrence intervals of a few months or less. We demonstrate this method using five storm events in a small (~15 km2), undeveloped, gravel‐bedded tributary of the Connecticut River (USA). We estimate that in each storm, the mass of sediment deposited onto the margins accounts for almost 90% of the sediment mobilized from the bed, with the remainder of the mobilized bed sediment transported downstream as suspended load. The result that the bed is a net source of sediment to the stream and the margins a net sink is robust, but estimates of the mass of material eroded from the bed and deposited on the margins are less certain. The source of sediment to the bed remains unclear as, consistent with earlier studies, we observe only limited deposition of sediment to the bed during the storm events. The suspended sediment is organic‐rich and thus its source may be associated with in‐channel organic decay between storm events. Understanding the coupled interactions between discharge magnitude and frequency and sediment resupply at the event time scale has important implications for stream restoration efforts seeking to connect the channel and the broader riparian zone, and for the development of accurate sediment budgets and predictions of sediment flux from a watershed. Copyright © 2015 John Wiley & Sons, Ltd.

Quantile Regression-Based Probabilistic Estimation Scheme for Daily and Annual Suspended Sediment Loads

Assessing suspended sediment loads in rivers is important since it affects water quality, hydraulic-facility design, and many other sediment-induced problems. Sediment-load estimation heavily depends upon empirical approaches such as a sediment rating curve, which is the empirical relationship between sediment load and river discharge. However, the sediment rating curve is insufficient to describe the inevitable scatter between sediment and discharge. This study aims to develop a probabilistic estimation scheme for daily and annual suspended sediment loads using quantile regression. All recorded daily suspended sediment load and discharge data are employed to construct quantile-dependent sediment rating curves. The empirical probability distribution of daily suspended sediment load is then built by integrating the conditional estimations associated with the corresponding quantiles for a given discharge. The probability distribution of a cumulative sediment load over a longer period can also be derived by the obtained daily sediment-load probability distributions and convolution theorem. The proposed approach is applied to the Laonung station located in southern Taiwan. The results indicate that the proposed approach provides not only the probabilistic description for daily and annual suspended sediment loads, but also the single estimations including the mean, median, and mode of the derived probability distribution. For the 1,110 recorded data of Laonung station during the 1959–2008 period, the proposed mean and median estimation schemes outperform the traditional sediment-rating-curve approach for less mean absolute errors.

Sedimentation in the Outer Hangzhou Bay, China: The Influence of Changjiang Sediment Load

Dai, Z.-j.; Liu, J.T.; Xie H.-l., and Shi, W.-y., 2014. Sedimentation in the outer Hangzhou Bay, China: The influence of Changjiang sediment load.Most estuaries in the world are facing the risk of subsidence due to insufficient sediment supply and relative sea-level rise. In the case of the world's fourth largest river, the Changjiang (aka Yangtze River), its river sediment load has been decreasing sharply, especially since the construction of the Three Gorges Dam. Due to the complexity in the estuarine dynamics, human activities, and the sediment supply, discerning whether the Changjiang Estuary is facing erosion or subsidence is a controversial issue. Immediately south of the mouth of the Changjiang is Hangzhou Bay. On the centennial time scale, accretion on the southern flank of the Changjiang deltaic plain has caused the seaward extension of the north bank of the Qiantang Estuary, leading to the formation of the macrotidal, funnel-shaped Hangzhou Bay. In this study, we used multiyear geographic information system (GIS)–rectified bathymetric charts of Hangzhou Bay for bathymetry and sediment-capacity change analysis. Our major findings show that the outer Hangzhou Bay has gone through the following stages: relatively steady sedimentation (1931–1997), erosional-depositional transition (1997–2002), and rapid erosion (2002–2008) at the rate of 58.5 × 106 m3/y. Our findings also corroborate measurements of suspended sediment discharge at the Datong station in the lower reaches of the Changjiang. Our findings confirm the dependence of the sedimentation in the outer Hangzhou Bay on the sediment supplied by the Changjiang. The severity of the erosion of the outer Hangzhou Bay and the sediment load decrease of the Changjiang might serve as a warning for the impending erosion of the Changjiang Estuary.

Prediction of Total Sediment Load in Sand-Bed Rivers in Korea Using Lateral Distribution Method

A new method for numerically predicting the total sediment load in a river is proposed. The method can be used to predict the total sediment load with information on channel geometry and slope, flow, and bed materials. The conventional method uses a 1D approach that assumes the channel has a wide rectangular shape. However, the proposed method computes depth-averaged velocity over the width and predicts the total sediment load based on the flow computations. The new method, therefore, is expected to predict better if the flow changes significantly in the lateral direction. The proposed method was applied to three large sand-bed rivers in Korea, where information is available regarding suspended sediment. Five formulas were tested of use in making total sediment load computations, namely Engelund-Hansen's, Ackers-White's, Yang's, Brownlie's, and Karim's formulas. The predicted total sediment loads are compared not only with measured data but also with results calculated using the 1D approach. Discrepancy ratios between the predicted and measured total sediment loads are given and the results are discussed.

Chapter 21 A review of sedimentation since the Last Glacial Maximum on the continental shelf of eastern China

Abstract The contiguous continental shelf of the Bohai, Yellow and East China seas has a total area of about 0.75×10 6 km 2 and a width of over 600 km. The basement is tectonically stable and the accumulated thickness of Quaternary sediment is up to 500 m. During the post-glacial period, the epicontinental shelf received a large influx of fluvial sediments with complex fluvial–marine interactions. The river-dominated shelf sedimentation is characterized by two types of terrigenous sediment source-to-sink transport processes represented by the two mega-rivers, Changjiang (Yangtze River) and Huanghe (Yellow River), and the small mountainous rivers in Taiwan Island, in total contributing about 10% of the world's total river sediment load. Mud patches and belts, and tidal sand ridges were well developed on the shelf during the post-glacial period. These muds are generally interpreted as eddy sedimentation formed after the highest post-glacial transgression, while the tidal sand ridges with several formation stages developed under variable oceanic regimes. The changes in monsoon climate-induced river flux, sea level and oceanic circulation primarily controlled the stratigraphic framework and sedimentary facies on the shelf during the late Quaternary. Nevertheless, many aspects of sedimentary processes and river–sea interactions at different spatial and temporal scales require more investigation.

Sediment load of the main rivers of Lake Baikal in a changing environment (east Siberia, Russia)

The results of the analysis of discharge and sediment flow changes of the main rivers flowing into Lake Baikal are presented. Long-term observation record of sediment flow is divided into two periods differing in average values and scale fluctuations of annual average values. During the first period, the dynamics of sediment flow of rivers was determined by hydro-climatic factors, i.e. fluctuations of sediment flow, in general, are synchronous to fluctuations of water flow. During the second period (from the mid-1970s) there is a downward trend of sediment flow change (decrease by 49%–82%) against the background of increased discharge of rivers. This trend is caused by both anthropogenic influence, and natural processes connected to global and regional changes of climatic characteristics. In general, natural processes of sediment flow changes in the different areas of Baikal basin are altered by anthropogenic factors to a greater or lesser extent. The present article can be used as analytical material for further research and forecast of sediment flow changes in the Baikal basin as well as in other rift-valley lakes of the world.

Hydrological and morphological processes at river mouths of the Caspian Sea Region as possible analogs of expected changes of mouths of other rivers in Russia and the world

Present changes in the regime and structure of mouths of rivers, which empty into the Caspian Sea, are discussed. The similarities and differences of these processes at the mouths of different rivers of the Caspian Region were revealed. Assessment was made of the impact of changes in river water runoff and sediment load and in the Caspian Sea level as well as the nearshore zone relief and local hydraulic engineering activities on the processes under study. Anomalous features of the processes occurring at the mouths of the Volga and Terek rivers were revealed and explained. Hydrological and morphological processes typical of the present mouths of the rivers of Ural, Sulak, and Kura were revealed; these processes could be accepted as universal and possible analogs in assessing the expected changes at the mouths of other rivers in Russia and the world in the XXI century.

Sediment balances in the Blue Nile River Basin

Rapid population growth in the upper Blue Nile basin has led to fast land-use changes from natural forest to agricultural land. This resulted in speeding up the soil erosion process in the highlands and increasing sedimentation further downstream in reservoirs and irrigation canals. At present, several dams are planned across the Blue Nile River in Ethiopia and the Grand Ethiopian Renaissance Dam is currently under construction near the border with Sudan. This will be the largest hydroelectric power plant in Africa. The objective of this paper is to quantify the river flows and sediment loads along the Blue Nile River network. The Soil and Water Assessment Tool was used to estimate the water flows from un-gauged sub-basins. To assess model performance, the estimated sediment loads were compared to the measured ones at selected locations. For the gauged sub-basins, water flows and sediment loads were derived from the available flow and sediment data. To fill in knowledge gaps, this study included a field survey in which new data on suspended solids and flow discharge were collected along the Blue Nile and on a number of tributaries. The comparison between the results of this study and previous estimates of the sediment load of the Blue Nile River at El Deim, near the Ethiopian Sudanese border, show that the sediment budgets have the right order of magnitude, although some uncertainties remain. This gives confidence in the results of this study providing the first sediment balance of the entire Blue Nile catchment at the sub-basin scale.

Assessment of total sediment load in rivers using lateral distribution method

A new numerical model for predicting the total sediment load in the river is presented. The model is comprised of two parts, namely flow and sediment transport parts. The flow analysis is carried out using the lateral distribution method, which distributes the flow and sediment load across the width, based on channel geometry and flow dynamics. To obtain the total sediment load, the bedload and suspended load are predicted separately. Conventional formulas are used for the bedload, and Rousean distribution with an entrainment function is used for the suspended load. Einstein partition is used to separate the form drag component from the total shear stress. The model is applied to the Danube River, a gravel-bed river in Slovakia and the Han River, a sand-bed river in Korea. Predicted distributions of sediment load in the lateral direction are given. The predicted results are compared with those obtained using the 1D approach as well as from measured data. Total sediment load rating curves are presented and the mixture effect of bed-materials is discussed.

Contribution of tropical cyclones to the sediment budget for coastal wetlands in Louisiana, USA

The storm surge from a single hurricane can deposit tens of millions of tons of sediment on coastal wetlands within 100 km of landfall, but the distribution and cumulative amount from hurricanes at a centurial timescale is unknown. Here we use a model calibrated by three storms to estimate the average deposition on the deteriorating Louisiana coast from 1851 to 2008. The total deposition on Louisiana coastal wetlands, exclusive of open water, averages 5.6 million tons of inorganic sediment per year, equivalent to 3.8 % of the modern annual Mississippi River sediment load. Seventy nine percent of this sediment is deposited in a 20 km strip along the Gulf of Mexico (7,400 km2 wetlands) comprised primarily of salt marshes, and this distribution matches spatial and temporal patterns described in modern surficial deposits and sediment cores. We estimate that surge-induced deposition of sediment is attributable to at least 65 % of the inorganic content of the top 24 cm of soils in abandoned delta lobes, and 80 % in the chenier plain. While the most sedimentation from a given event results from the most intense storms, 78 % of the long-term hurricane sedimentation results from moderate storms (930–990 mb) that comprise 51 % of tropical cyclone events. Furthermore, we estimate that the 47 % of storms that make landfall with an internal barometric pressure above 990 mb account for only 7 % of the tropical cyclone sedimentation on wetlands.

Impacts of agricultural land-use dynamics on erosion risks and options for land and water management in Northern Mongolia

In Mongolia, nomadic herders have successfully been grazing livestock for more than a millennium. However, in recent years, concerns have increased that changes in management and higher livestock stocking rates may negatively affect vegetation and increase soil erosion, overland flow and sediment load of rivers. In addition, ambitious agricultural policies increase the intensity of agricultural land use thus enforcing a conversion of grassland to agricultural land which is far more susceptible to erosion. In this study, we tackle the question how recent land-use dynamics influence erosion risks and which implications these require on water resources management. The study was part of a larger research effort, studying implementation options for Integrated Water Resources Management (IWRM); in this paper, specifically impacts of land use and land-use change on water resources are studied. The study has been carried out in the Kharaa river basin (KRB) in Northern Mongolia, in which grazing and agriculture play key roles. As several erosion and run-off-relevant factors such as slope, soil type or land use and land cover are widely varying in the KRB, sub-regions of the catchment have been analysed to identify susceptible combinations of environmental and land management factors. In our study we identified that erosion risks in the sub-catchments under current land use and management calculated with the Revised Universal Soil Loss Equation sum up to approximately 2–4 Mg ha−1 year−1 for steppe and 4–9 Mg ha−1 year−1 for croplands, while erosion rates calculated using 137CS measurements resulted in 2–3 Mg ha−1 year−1 on steppe and 15 Mg ha−1 year−1 on cropland. Erosion risk scenarios indicate that land use change as well as management and climate factors can reduce (−30 %) or aggravate erosion risks up to sevenfold and contribute to additional challenges in water and soil management in the KRB. Strategies have to be developed to limit land conversion and implement soil protection in erosion prone sub-regions. IWRM has the potential to bridge sectorial measures, e.g. in agriculture, rural development or nature protection, but erosion and runoff-related impacts currently are addressed in different institutions, legal frameworks and regulations, which may slow down or hamper efficient measures.

Sediment load and carbon burial in the Yellow River during the Holocene

Sediment load and carbon burial in the Yellow River during the Holocene

Shoreline change of Chongming Dongtan and response to river sediment load: A remote sensing assessment

Summary Chongming Dongtan, located in the center of the Yangtze estuary, is a Ramsar Wetland of International Importance and National Nature Reserve. The dramatic decrease in river sediment load has attracted considerable scientific interest to this area, but few studies have paid attention to the shoreline dynamics. This study uses Landsat images spanning from 1987 to 2010 and an orthogonal transect method, which was previously developed by the authors, to model the spatial and temporal characteristics of shoreline change and explore its relationship to reduced river sediment load by use of regression analysis on three different spatial scales. Results show a general decrease in the average rates of shoreline change throughout the entire study period. The maximum average shoreline change rate of +115.5 m/year occurred in the 1987–1990 interval and the minimum rate of +20.4 m/year occurred from 2006 to 2008. Based on average rates of shoreline change, the coast of Dongtan was divided into three segments: the erosion segment, eastern accretion segment, and northern accretion segment. The temporal pattern of the northern accretion segment is almost completely opposite to that of the eastern accretion segment. The strongest-correlation transects are located on the northern side of the eastern tip of Dongtan and the next strongest transects are located on the south side. Other transects have a very low correlation. Transect 19 near the easternmost tip of Dongtan has a near zero correlation (r2 = 0.0045) but has the fastest accretion rate, and in general an increase in the shoreline change rate. The average rate of shoreline change and the net accretion area in Dongtan as a whole are significantly associated with sediment discharge at Datong Station (r2 = 0.69 and 0.75, respectively). This implies that shoreline accretion in Dongtan will probably slow down gradually, if the river sediment load continues to decrease in the future. The shoreline change rates achieved using our approach are consistent with previous studies, but the relationship with the river sediment load is different from results in a previous study on intertidal wetland based on bathymetric maps. The results and methods may be helpful in coastal management and understanding the evolution of the entire delta from the perspective of shoreline change.

Applying regression analysis to calculating suspended sediment runoff: Specific features of the method

Major theoretical prerequisites for the application of regression analysis are considered as applied to calculating suspended sediment given observational data on water discharge and sediment load in rivers. A concept of sediment transport curve as a calculation model based on regression analysis is introduced. The role of the probabilistic structure of raw data in the determination of the optimal form of sediment transport curve and the potential structure of errors of regression models is discussed. The most widely used theoretical models of curves, as well as the methods and algorithms for assessing regression coefficients are analyzed. The application limits and the accuracy of the method are derived from its stochastic nature, and the most common methodological mistakes in its use are discussed.

Hydrological responses to the combined influence of diverse human activities in the Pearl River delta, China

In this paper, temporal variations in the hydrological process of the Pearl River delta (PRD) are examined based on monthly datasets for water discharge, sediment load and suspended sediment concentration (SSC) since the 1950s using the methods of power spectrum analysis and Fourier transform. In addition, the underlying causes of the variations are examined to address the influence of diverse human activities on hydrological process. The results indicate that (1) for the monthly low pass filtering series with a timescale of more than 8a, the water discharge from the Pearl River increased insignificantly with an average rate of 1.66m3/s per year, whereas the sediment load and SSC decreased significantly with an average rate of 18.54kg/s and 0.002kg/m3 per year, respectively, between 1957 and 2009; (2) decadal change in the water discharge of the Pearl River can be identified with low periods in 1950s–1972, 1984–1992 and 2003–2009 and high periods in 1973–1983 and 1993–2002, which is in good agreement with precipitation changes. Decadal change in the sediment load generally differed among three tributaries. For the West River and the North River, before the 1970s, no significant change in the sediment load can be observed because of the balanced influences of dam construction and deforestation. In the 1980s, a significant increase occurred because deforestation exceeded dam construction. Since the 1990s, large reservoirs were constructed in the West River and North River basins. And total deposition rate of all the reservoirs in two river basins was estimated to be 168.8×106m3/a in the 1990s and reached to 881.1×106m3/a in the 2000s, respectively. The influences of dam construction and soil conservation have outweighed the impact of deforestation, which has resulted in a significant decrease in the sediment load. For the East River, since the dam construction in 1960, the influence of deforestation on the sediment load did not outweigh the influence of the dam construction, which gradually decreased the sediment load; (3) for the PRD, temporal change in the water discharge and sediment load in the West River and North River deltas correspond well with the change in the water discharge and sediment load upstream of the West River and the North River before the 1990s. Due to the uneven down-cutting of the riverbed in the upper PRD since the mid-1980s, which is primarily caused by intensified sand excavation from the river channel, the divided flow ratio and divided sediment ratio at Sanshui station in the North River delta increased by 7.8% and 7.7%, respectively, in the 1990s–2000s compared with the 1960s–1980s. Therefore, the water discharge and sediment load in the North River delta increased by 57.0% and 12.2%, respectively. These changes have resulted in morphological changes in the PRD and caused many environmental problems across the PRD, which should be paid special attention.

Development of a time-stepping sediment budget model for assessing land use impacts in large river basins

The use of river basin modelling to guide mitigation of non-point source pollution of wetlands, estuaries and coastal waters has become widespread. To assess and simulate the impacts of alternate land use or climate scenarios on river washload requires modelling techniques that represent sediment sources and transport at the time scales of system response. Building on the mean-annual SedNet model, we propose a new D-SedNet model which constructs daily budgets of fine sediment sources, transport and deposition for each link in a river network. Erosion rates (hillslope, gully and streambank erosion) and fine sediment sinks (floodplains and reservoirs) are disaggregated from mean annual rates based on daily rainfall and runoff. The model is evaluated in the Burdekin basin in tropical Australia, where policy targets have been set for reducing sediment and nutrient loads to the Great Barrier Reef (GBR) lagoon from grazing and cropping land. D-SedNet predicted annual loads with similar performance to that of a sediment rating curve calibrated to monitored suspended sediment concentrations. Relative to a 22-year reference load time series at the basin outlet derived from a dynamic general additive model based on monitoring data, D-SedNet had a median absolute error of 68% compared with 112% for the rating curve. RMS error was slightly higher for D-SedNet than for the rating curve due to large relative errors on small loads in several drought years. This accuracy is similar to existing agricultural system models used in arable or humid environments. Predicted river loads were sensitive to ground vegetation cover. We conclude that the river network sediment budget model provides some capacity for predicting load time-series independent of monitoring data in ungauged basins, and for evaluating the impact of land management on river sediment load time-series, which is challenging across large regions in data-poor environments.

Assessing dam pool sediment for understanding past, present and future watershed dynamics: An example from the Cuyahoga River, Ohio

Abstract Dams can trap a stream's sediment load and create a sediment record of anthropogenic watershed impacts and stream sediment load variability. We demonstrate the usefulness of dam pool sediments in assessing past, present, and future watershed dynamics in this study of the Gorge Dam Pool, Cuyahoga River, Ohio. The 17.4-m-tall Gorge Dam was constructed in 1912 and subsequently trapped the sediment load of the Middle Cuyahoga River. 210 Pb dating of the impoundment sediment allowed past anthropogenic impacts to be assessed. Mud accumulating between 1912 and 1926 has high trace metal content from industrial activities upstream of the impoundment. Between 1926 and 1978 mud having abundant coal combustion products (CCP) and high but variable metal content accumulated. During this period, sediment accumulation increased due to urbanization in the watershed. Since 1978 CCP and trace metals decline, reflecting the effectiveness of environmental regulations. Sediment accumulation increased dramatically between 2004 and 2008 and again in 2011 as a result of increased extreme flow events. An impoundment sediment accumulation of 7520 tonnes yr −1 for the 210 Pb-dated year 2006 is similar to a watershed model estimate of 7490 tonnes yr −1 determined from year 2006 landcover and supports the use of watershed modeling to estimate sediment load. Dam removal to reestablish river connectivity also eliminates the impoundment sediment trap. The impoundment sediment load record allows for a projection to the downstream sediment load following dam removal. The potential removal of the Gorge Dam will result in a minimal increase to the Lower Cuyahoga River sediment load.