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1.
The impact of dredge spoil disposal on asymmetrical large-scale dunes has been studied at a disposal site in a shallow subtidal area of the outer Weser Estuary (German Bight, southeastern North Sea). Between June and December 1998, this site was used for the disposal of ~3×106 m3 dredge spoil. Repeated bathymetric surveys with a multibeam echosounder system reveal that the artificial supply of sediment provoked significant morphological changes in the dune field, including the infill of dune troughs and even the complete burial of individual dunes. However, even completely buried dunes began to regenerate within a few months. In addition, slow migration of the dunes toward the open sea was observed, indicating net seaward sediment transport in the survey area. Since the dumped sediment does not appear to have a persistent effect on the bedforms and, in all likelihood, will be exported from the estuarine system on medium- to long-term timescales, the investigated area constitutes a suitable disposal site.  相似文献   

2.
Distribution of particulate organic carbon (POC) and dissolved organic carbon (DOC) in seawater, and chemical composition of surficial sediments were studied in relation to pulpmill effluent and dumping of dredge spoil containing wood debris in Alberni Inlet, British Columbia, Canada. The maximum concentration of POC (377–584µg Cl–1) was observed at the surface around the dumping area (5–7 km seaward of the inlet's head), and at the location immediately adjacent to the dump site POC was elevated throughout the water column (50 m). While POC tended to decrease in the surface layer for a distance of about 25km down-inlet, measureable effects of POC in the deeper water did not extend beyond 600m from the dump site. The dump site was conspicuous by the large maximum in C:N ratio (46.3). In contrast, DOC was observed to be highest (4.25mg Cl–1) at the head of the inlet where pulpmill effluent was being discharged and a secondary maximum was found about 10km down-inlet from the dump site. The data suggest that a considerable proportion of the dredge spoil sinks rapidly near the dump site, probably within several hundred metres. Some of the spoil, perhaps low density wood debris may travel considerably further with the surface water where by leaching it may contribute to some extent to the surface DOC before sinking into deeper water.  相似文献   

3.
倾倒区容量主要受海水动力过程(潮流输沙、风暴潮和风浪掀沙等)、倾倒区面积和水深地形等因素影响。本文基于FVCOM(Finite Volume Coast and Ocean Model)三维数值模型和随机动态统计分析模型, 利用倾倒区地形演变和倾倒量资料, 探讨海水动力过程(潮流输沙、风暴潮和风浪掀沙等)和倾废活动对海底地形变化的影响, 构建海洋倾倒区容量长期演变评估模型。利用FVCOM水动力和泥沙模型计算自然状态下潮流输沙引起的地形变化, 同时结合倾倒区多年实测水深和倾倒量资料, 分析倾倒量、潮流输沙和地形变化的统计关系, 通过实际资料拟合修订系数, 作为该倾倒区海浪和风暴潮等因素输沙所造成地形变化的参考值, 以此评估倾倒区容量长期演变。在设定实际地形变化阈值的前提下, 计算倾倒区容量。以长江口1#倾倒区为例, 1#倾倒区地形抬升0.5m/a,倾倒区容量约为670万方/a,模型结果和实际批复结果吻合。同时在甬江口2#倾倒区、罗源湾倾倒区、嵊泗上川山、东碇倾倒区和温州港倾倒区等验证, 模拟结果同实际观测结果相近。  相似文献   

4.
Between 1970 to 2000, the annual mean suspended matter (SPM) concentrations in the Vlie and Marsdiep tidal inlets of the Wadden Sea varied over five times. The present paper examines the possible relationship between SPM in the Wadden Sea and changing river Rhine discharges and dredging operations. The major short-term variations in annual mean SPM in part of the Wadden Sea appears to be a non-linear, exponential, function of river Rhine discharge and dredge spoil disposal (110 km to over 200 km from the area in front of the Dutch coast near the river Rhine outlet). Correlation coefficients (with SPM as the fixed and dredge disposal as the independent variable) ranged from R=0·8 (deep tidal inlet of Marsdiep) to R=0·2 (shallow inner area of Vlie) and weakened mainly as a function of distance to the disposal site. The best correlation with river discharge was for Marsdiep tidal inlet (r=0·45), indicating the superior effect of dredge disposal over river discharge-related processes. Taking the estimated regression equation as an explorative model, indicates that, without any disposal of dredge spoil, the expected SPM concentration levels in the tidal inlets of the Wadden Sea will be <15 g m−3 (comparable to the 1950s). The overall mean (and the highest mean) annual concentrations for the investigation period reached 42 (90) g m−3 at Marsdiep and 35 (75) g m−3 at Vlie. Assuming a 10% (220 m−3 s−1) increase in river Rhine discharge over the next 50 years, and unchanged dredging policy and other circumstances, SPM concentrations would increase 5–15% for Marsdiep and Vlie. Compared with the calculated (12·4 g m−3 SPM in Marsdiep and 14·8 g m−3 SPM in Vlie) and measured (15 g m−3 SPM in Marsdiep) background SPM concentrations, the expected overall mean increase since 1950 is at least 250% of background. The natural variation in river Rhine discharge will cause further inter-annual variation. Changes in SPM concentrations, due to expected changes in wind climate, combined with river discharge are estimated to increase SPM concentrations 20% above the present situation. The possible implications of changes in land use in combination with further increasing river discharge, changed wind fields and increased temperature are discussed. An important management conclusion is that increasing mean river discharge will significantly increase the need for dredging and spoil disposal, and result in further elevated SPM concentrations in the Dutch coastal zone and the Wadden Sea. The presented relationships offer possibilities for developing new management strategies in relation to dredging and its effects.  相似文献   

5.
A large deficit in the coastal sediment budget, high rates of relative sea-level rise (~0.9 cm/year), and storm-induced current and wave erosion are forcing barrier shoreface retreat along the periphery of the Mississippi River delta plain. Additionally, conversion of interior wetlands to open water has increased the bay tidal prism, resulting in degradation of barrier islands due to inlet widening, formation of new inlets, and sediment sequestration at ebb-tidal deltas. Single-beam bathymetric surveys along a 165-km stretch of south-central Louisiana barrier coast, from Raccoon Point in Terrebonne Parish to Sandy Point in Plaquemines Parish, were conducted in 2006. These data, combined with historical bathymetry from three time periods (dating to the 1880s), provide a series of digital elevation models that were used to calculate sediment volumetric changes and determine long-term erosional-depositional trends. Dominant patterns during the 125-year period include (1) erosion of ~1.6 × 109 m3 from the shoreface, forcing up to 3 km of shoreface retreat, (2) sediment deposition in coastal bights and at ebb-tidal deltas, and (3) a combined increase in tidal inlet cross-sectional area from ~41,400 m2 to ~139,500 m2. Bathymetric and shoreline change datasets separated by shorter time periods (sub-annual) demonstrate that these long-term trends are driven by processes associated with major hurricane impacts, and that rates of shoreface erosion are an order of magnitude greater during active hurricane seasons compared to long-term trends.  相似文献   

6.
东碇临时海洋倾倒区是当前福建省内使用频率最高、倾倒量最大的海洋倾倒区,自2010年重新投入使用以来,该倾倒区共接纳了约1.5×107 m3的疏浚物,为研究其海底地形冲淤变化情况,利用ArcGIS的空间分析模块、3D分析模块、地统计分析模块等对东碇临时海洋倾倒区进行冲淤变化分析,文中介绍了冲淤分析的基本流程并对分析结果进行讨论,说明疏浚物倾倒对水深地形的影响程度。  相似文献   

7.
长江口深水航道以悬沙落淤为主,回淤泥沙较为松散、上覆有流动性较强的高密度浮泥层,航槽需进行常年维护。为提高疏浚效率、降低疏浚成本,基于耙头动力改进的思路,提出适用于长江口沉积物特性的掺气扰动耙具,并通过室内试验,探讨耙具推荐型式,推荐空压机流量及压力指标,估算掺气耙具扰动效果。结果表明,2 mm气嘴耙具掺气扰动后水体含沙量增幅高于其他孔径;相同孔径、相同气流量下,气嘴间距越大、扰动效果越明显,因此推荐耙具气嘴孔径2 mm、20 cm间距交错布置型式。对于推荐耙型,当气体压力低于4.8×105Pa、气流量小于1.1 m3/min时,扰动后水体含沙量基本呈线性增长;当气体压力超过4.8×105Pa,扰动后水体含沙量无明显变化。以室内试验推荐压力4.5×105Pa为基础,估算施工作业水深15 m,结合实际作业水深及气力损耗,现场空压机选型参考值为气流量61.7 m3/min、工作压力为0.7 MPa。据此推算设计航速1.286 m/s时,中上层(0～4 m)水体掺气扰动疏浚耙具悬扬原状土方量约800 m3/h。  相似文献   

8.
The results of four MAFF surveys (1975–1980) of the sediments in and around the sewage sludge dumping site in Liverpool Bay are presented. Sediments were analysed for particle size distribution, organic carbon concentrations and concentrations of Hg, Cd, Cu, Zn, Pb, Ni and Cr. Concentrations of organic carbon and metals were found to be elevated in the fine ( < 90 μm) fraction in areas associated with the major inputs of these substances to the bay—near the mouth of the Mersey, near the sewage sludge dumping site and at the dredged spoil dumping site.In an attempt to determine any temporal trends between surveys, stations were grouped into four 8×8 km areas from offshore of the dumping ground to the mouth of the Mersey. Changes in the metal concentrations in sediments in the square nearest the sewage sludge dumping site were larger than in the other squares including that nearest the Mersey. Comparison of temporal trends near the sewage sludge site with the quantities actually dumped showed a correlation between the two, consistent with sewage sludge dumping being a major contributor to the metal levels in fine sediments near the dumping ground.  相似文献   

9.
Over 4 years, repetitive bathymetric measurements of a shipwreck in the Grådyb tidal inlet channel in the Danish Wadden Sea were carried out using a state-of-the-art high-resolution multibeam echosounder (MBES) coupled with a real-time long range kinematic (LRK?) global positioning system. Seven measurements during a single survey in 2003 (n=7) revealed a horizontal and vertical precision of the MBES system of ±20 and ±2 cm, respectively, at a 95% confidence level. By contrast, four annual surveys from 2002 to 2005 (n=4) yielded a horizontal and vertical precision (at 95% confidence level) of only ±30 and ±8 cm, respectively. This difference in precision can be explained by three main factors: (1) the dismounting of the system between the annual surveys, (2) rougher sea conditions during the survey in 2004 and (3) the limited number of annual surveys. In general, the precision achieved here did not correspond to the full potential of the MBES system, as this could certainly have been improved by an increase in coverage density (soundings/m2), achievable by reducing the survey speed of the vessel. Nevertheless, precision was higher than that reported to date for earlier offshore test surveys using comparable equipment.  相似文献   

10.
根据2014年1月及2017年2月杭州湾大、小潮水沙资料,计算了流速、含沙量、单宽潮量、单宽输沙量,进而分析了潮周期断面净潮量、净输沙量和区域冲淤分布。研究发现杭州湾涨、落潮平均流速比值整体较20世纪八九十年代增大,绝大部分区域大于1.0,涨潮流相对增强,澉浦南岸和金山北岸尤为显著。含沙量平面上分布澉浦、杭州湾南岸两个高值区(大潮大于3 kg/m3,小潮大于1.3 kg/m3)以及北岸湾口至乍浦之间的低值区(大潮小于2 kg/m3,小潮小于0.9 kg/m3),随潮汛变化显著,最大含沙量浓度通常滞后于急流时刻。各测站涨、落潮量和输沙量呈现“大涨大落”和“大进大出”的特征,造成杭州湾短时间尺度内的“大冲大淤”。大潮两涨两落金山与乍浦、乍浦与澉浦之间区域净输沙量可达几千万吨,净冲淤则在几百万吨。  相似文献   

11.
Analysis of four historical bathymetric surveys over a 132-year period has revealed significant changes to the morphology of the San Francisco Bar, an ebb-tidal delta at the mouth of San Francisco Bay estuary. From 1873 to 2005 the San Francisco Bar vertically-eroded an average of 80 cm over a 125 km2 area, which equates to a total volume loss of 100 ± 52 million m3 of fine- to coarse-grained sand. Comparison of the surveys indicates the entire ebb-tidal delta contracted radially, with the crest moving landward an average of 1 km. Long-term erosion of the ebb-tidal delta is hypothesized to be due to a reduction in the tidal prism of San Francisco Bay and a decrease in coastal sediment supply, both as a result of anthropogenic activities. Prior research indicates that the tidal prism of the estuary was reduced by 9% from filling, diking, and sedimentation. Compilation of historical records dating back to 1900 reveals that a minimum of 200 million m3 of sediment has been permanently removed from the San Francisco Bay coastal system through dredging, aggregate mining, and borrow pit mining. Of this total, ∼54 million m3 of sand-sized or coarser sediment was removed from central San Francisco Bay. With grain sizes comparable to the ebb-tidal delta, and its direct connection to the bay mouth, removal of sediments from central San Francisco Bay may limit the sand supply to the delta and open coast beaches.  相似文献   

12.
The geomorphology, drainage systems and predominant lithologies of western Lebanon are briefly described as a background for sediment transportation into the eastern Mediterranean. Fragmentary past and current bathymetric work over offshore Lebanon is reviewed and a simplified compilation bathymetric map correlating and interpreting the different survey results is presented. It reveals a narrow continental shelf about 3 km in width with two wider areas in the north and south; the shelf break occurs generally at about 100 m depth. Submarine valleys are common, most of which are seaward continuations of important land valleys but some prolong land-fault trends. Many continue down the continental slope, dividing into “distributaries”. Hydrological data indicate that over 2,525 × 106 m3 of surface-water runoff annually discharges into the sea through the perennial streams of western Lebanon. A high proportion of the country exposes carbonate rocks but a number of the stream basins drain appreciable areas of soft clastics; preliminary work suggests that these contribute appreciable loads into the Mediterranean. Overall marine net sediment transport is northwards by the longshore current and predominant WSW-ENE directed waves, but investigations in progress indicate that the submarine valleys provide avenues for cross-shelf and down-slope movement for much sediment.  相似文献   

13.
Historical changes in the hydrology, sedimentology, and physical oceanography of the Columbia River Estuary have been evaluated with a combination of statistical, cartographic, and numerical-modelling techniques. Comparison of data digitized from US Coast and Geodetic Survey bathymetric surveys conducted in the periods 1867–1875, 1926–1937, and 1949–1958 reveals that large changes in the morphology of the estuary have been caused by navigational improvements (jetties, dredged channels, and pile dikes) and by the diking and filling of much of the wetland area. Lesser changes are attributable to natural shoaling and erosion. There has been roughly a 15% decrease in tidal prism and a net accumulation of about 68 × 106m3 of sediment in the estuary. Large volumes of sediment have been eroded from the entrance region and deposited on the continental shelf and in the balance of the estuary, contributing to formation of new land. The bathymetric data indicate that, ignoring erosion at the entrance, 370 to 485 × 106m3 of sediment has been deposited in the estuary since 1868 at an average rate of about 0.5 cm y−1, roughly 5 times the rate at which sea level has fallen locally since the turn of the century.Riverflow data indicate that the seasonal flow cycle of the Columbia River has been significantly altered by regulation and diversion of water for irrigation. The greatest changes have occurred in the last thirty years. Flow variability over periods greater than a month has been significantly damped and the net discharge has been slightly reduced. These changes in riverflow are too recent to be reflected in the available in the available bathymetric data.Results from a laterally averaged, multiple-channel, two-dimensional numerical flow model (described in Hamilton, 1990) suggest that the changes in morphology and riverflow have reduced mixing, increased stratification, altered the response to fortnightly (neap-spring) changes in tidal forcing, and decreased the salinity intrusion length and the transport of salt into the estuary.The overall effects of human intervention in the physical processes of the Columbia River Estuary (i.e. decrease in freshwater inflow, tidal prism, and mixing; increase in flushing time and fine sediment deposition, and net accumulation of sediment) are qualitatively similar to those observed in less energetic and more obviously altered estuarine systems. A concurrent reduction in wetland habitats has resulted in an estimated 82% reduction in emergent plant production and a 15% reduction in benthic macroalgae production, a combined production loss of 51,675 metric tons of organic carbon per year. This has been at least partially compensated by a large increase in the supply of riverine detritus derived from freshwater phytoplankton primary production. Comparison of modern and estimated preregulation organic carbon budgets for the estuary indicates a shift from a food web based on comparatively refractory macrodetritus derived from emergent vegetation to one involving more labile microdetritus derived from allochthonous phytoplankton. The shift has been driven by human-induced changes to the physical environment of the estuary.While this is a relatively comprehensive study of historical physical changes, it is incomplete in that the sediment budget is still uncertain. More precise quantification of the modern estuarine sediment budget will require both a better understanding of the fluvial input and dredging export terms and a sediment tranport model designed to explain historical changes in the sediment budget. Oceanographic studies to better determine the mechanisms leading to the formation of the turbidity maximum are also needed. The combination of cartography and modelling used in this study should be applicable in other systems where large changes in morphology have occurred in historical time.  相似文献   

14.
Sediment management is becoming a critical issue around the world, particularly where the development of Harbor facilities, the conservation of coastal environments and needs of tourism compete for sustainable use of sediment resources. In order to apply an Integrated Coastal Zone Management policy, new approaches for management of the dredged harbor material need to be considered by the scientific community and local stakeholders. The information contained in the Italian Ministry of the Environment Acts related to dredging of Carrara Harbor determined the sediment volume dredged between 1993 and 2008 (849,500 m3) and allows us to estimate an average rate of material dredged from the harbor mouth (10,000-13,000 m3/yr). Different management options were chosen by the authorities based on the contamination level of dredged sediment: nourishment (344,500 m3), offshore dumping (305,000 m3), disposal in landfill (10,000 m3) or in Confined Disposal Facilities (215,000 m3). The present study’s goal is to determine the sedimentary budget of the Apuo-Versilian coast and to use the result to guide a compensation strategy to reduce the sediment deficit caused by the disposal of sediments out of the sand-sharing system. In particular, the present study provides a detailed reference frame that can lead to adopt a compensation strategy to balance the eroding evolutionary trend of the coastline adjacent to shallow water dredging areas. The procedure described in the paper is a policy initiative based on scientific results and could provide a model for other jurisdictions developing their own sediment quantitative estimation within an ICZM approach and a sustainable development of sedimentary resource’s management.  相似文献   

15.
１９９２年１０月在“珠江口航道整治规划”研究中应用中子活化示踪沙技术对矾石浅滩抛泥区泥沙的运动规律及其对航道的回淤影响进行了现场测验，就该抛泥区的合理性进行了分析。该抛泥区所抛泥沙主要沿矾石浅滩南移沉积，另有一部分西行进入伶仃航道，为减少航道的淤积，该抛泥区应适当向东迁移。  相似文献   

16.
In order to study the mechanism of flow-sediment movement, it is essential to obtain measured data of water hydrodynamic and sediment concentration process with high spatial and temporal resolution in the bottom boundary layer （BBL）. Field observations were carried out in the northwest Caofeidian sea area in the Bohai Bay. Near 2 m isobath （under the lowest tidal level）, a tripod system was installed with AWAC （Acoustic Wave And Current）, ADCP （Acoustic Doppler Current Profilers）, OBS-3A （Optical Backscatter Point Sensor）, ADV （Acoustic Doppler Velocimeters）, etc. The accurate measurement of the bottom boundary layer during a single tidal period was carried out, together with a long-term sediment concentration measurement under different hydrological conditions. All the measured data were used to analyze the characteristics of wave-current-sediment movement and the BBL. Analysis was performed on flow structure, shear stress, roughness, eddy viscosity and other parameters of the BBL. Two major findings were made. Firstly, from the measured data, the three-layer distribution model of the velocity profiles and eddy viscosities in the wave-current BBL are proposed in the observed sea area; secondly, the sediment movement is related closely to wind-waves in the muddy coast area where sediment is clayey silt： 1） The observed suspended sediment concentration under light wind conditions is very low, with the peak value generally smaller than 0.1 kg/m^3 and the average value being 0.03 kg/m^3; 2） The sediment concentration increases continuously under the gales over 6-7 in Beaufort scale, under a sustained wind action. The measured peak sediment concentration at 0.4 m above the seabed is 0.15-0.32 kg/m^3, and the average sediment concentration during wind-wave action is 0.08-0.18 kg/m^3, which is about 3-6 times the value under light wind conditions. The critical wave height signaling remarkable changes of sediment concentration is 0.5 m. The results show that the suspended load sediment concentration is mainly influenced by wave-induced sediment suspension.  相似文献   

17.
The purpose of this study was to evaluate related processes of sediment consolidation and resuspension in a coastal basin and how these processes influence retention of fine sediment delivered by a river diversion. Sediment samples were collected from Lake Lery, a coastal receiving basin of the Caernarvon Diversion from the Mississippi River, Louisiana. Consolidation was tested for six initial sediment concentrations (14.0–105 kg m–3) in a settling column over 15-day periods. Mud erodibility was tested at seven shear stress regimes (0.01–0.60 Pa) using a dual-core Gust erosion microcosm system, on cores containing suspensions that consolidated for 1, 2, and 4 weeks. Consolidation rates were found to be inversely and exponentially related to initial suspension concentration, over concentrations ranging from fluid mud (10–200 kg m–3) to hydraulic dredge effluent. Consolidation is best predicted by a function consisting of two exponential terms and one asymptotic constant, describing rates of rapid initial and slower subsequent settling. Coupled resuspension and consolidation tests (concentrations of 20–21 kg m–3) show that shear stresses generating the highest turbidity peaks increase from ≤0.30 Pa after 2 weeks of consolidation to ≥0.45 Pa after 4 weeks, and this strengthening cannot be attributed solely to increasing sediment concentration over time. Comparison of measured erosion shear stresses with bed shear stresses typical of coastal lakes and bays suggests that this degree of strengthening, if given time to occur, could increase the overall retention of fine sediments deposited on lake and bay floors.  相似文献   

18.
Since 1976, the main channel of the Yellow River (Huanghe) has been on the east side of the delta complex, and the river has prograded a broad new delta lobe in Laizhou Bay of the Bohai Sea. In 2012, extensive bathymetric and high-resolution seismic profiles were conducted and sediment cores were collected off the new delta lobe. This study examined delta sedimentation and morphology along a profile across the modern subaqueous Yellow River delta and into Laizhou Bay, by analyzing sediment radionuclides (137Cs, 210Pb and 7Be), sedimentary structure, grain-size composition, organic carbon content, and morphological changes between 1976 and 2012. The change in the bathymetric profile, longitudinal to the river’s course, reveals subaqueous delta progradation during this period. The subbottom boundary between the new delta lobe sediment and the older seafloor sediment (before the 1976 course shift) was identified in terms of lithology and radionuclide distributions, and recognized as a downlap surface in the seismic record. The accumulation rate of the new delta lobe sediment is estimated to be 5–18.6 cm year–1 on the delta front slope, 2 cm year–1 at the toe of the slope, and 1–2 cm year–1 in the shelf areas of Laizhou Bay. Sediment facies also change offshore, from alternations of gray and brown sediment in the proximal area to gray bioturbated fine sediment in the distal area. Based on 7Be distribution, the shorter-term deposition rate was at least 20 cm year–1 in the delta front.  相似文献   

19.
Scallops are usually obtained by means of a heavy metal dredge that is pulled over the sea bottom. Most studies of the impact of this gear type have shown that larger invertebrates, in particular, are severely disturbed. These studies, however, have been conducted on coarse sediments, ranging from sands to cobble, and have dealt only with faunal changes. In this paper the impact of a New England type scallop dredge on the fauna and sedimentary nutritional characteristics of a silty sand community is detailed. The site, in the Damariscotta River, Maine, USA, was sampled during the fall and winter prior to, then again immediately following, the dragging event, and twice more over the ensuing six months. Loss of surficial sediment, lowered food quality of the sediment (as measured by microbial populations, enzyme hydrolysable amino acids, and chlorophyll a), and changes in the faunal composition of the dragged site were observed. While some taxa returned to the drag track relatively quickly, others such as the cumaceans, phoxocephalid and photid amphipods, and nephtyid polychaetes, were not seen in abundances comparable to those of the adjacent undragged site until the food quality also recovered.  相似文献   

20.
We examined short-term phytoplankton and sediment dynamics in Tampa Bay with data collected between 8 December 2004 and 17 January 2005 from optical, oceanographic, and meteorological sensors mounted on a coastal oceanographic tower and from satellite remote sensing. Baseline phytoplankton (chlorophyll-a, Chl) and sediment concentrations (particle backscattering coefficient at 532 nm, bbp(532)) were of the order of 3.7 mg m−3 and 0.07 m−1, respectively, during the study period. Both showed large fluctuations dominated by semidiurnal and diurnal frequencies associated with tidal forcing. Three strong wind events (hourly averaged wind speed >8.0 m s−1) generated critical bottom shear stress of >0.2 Pa and suspended bottom sediments that were clearly observed in concurrent MODIS satellite imagery. In addition, strong tidal current or swells could also suspend sediments in the lower Bay. Sediments remained suspended in the water column for 2–3 days after the wind events. Moderate Chl increases were observed after sediment resuspension with a lag time of ˜1–2 days, probably due to release of bottom nutrients and optimal light conditions associated with sediment resuspension and settling. Two large increases in Chl with one Chl > 12.0 mg m−3 over ˜2 days, were observed at neap tides. For the study site and period, because of the high temporal variability in phytoplankton and sediment concentrations, a monthly snapshot can be different by −50% to 200% from the monthly “mean” chlorophyll and sediment conditions. The combination of high-frequency observations from automated sensors and synoptic satellite imagery, when available, is an excellent complement to limited field surveys to study and monitor water quality parameters in estuarine environments.  相似文献   

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