Tidal Delta Research Articles

Pollution evaluation and health risks assessment of naturally occurring toxic metals in shallow groundwater: A study in southwestern tidal delta of Bangladesh

Groundwater is the main source of potable water in rural regions of Bangladesh. Still, contamination with potentially harmful metals due to natural processes and anthropogenic activities leads to various health impacts. The focus of this research was to determine the extent of metal contamination in shallow groundwater from three southwestern districts of Bangladesh and the health hazards associated with it. A comprehensive analysis of metal, including metalloid, copper (Cu), aluminum (Al), chromium (Cr), Arsenic (As), Manganese (Mn), and boron (B) was performed on a set of 51 samples. Groundwater samples were analyzed for contamination using Atomic Absorption Spectroscopy and a UV–VIS Spectrophotometer, with pollution levels assessed via indices like the Metal Evaluation Index, Nemerow Pollution Index, and Contamination Index. Human health risks were evaluated through Chronic Daily Intake, Hazard Quotient, and Hazard Index calculations following USEPA guidelines. The results indicate that arsenic levels exceeded 25 samples and manganese levels exceeded 34 samples in accordance with WHO drinking water standards. Boron (B) concentrations exceeded the threshold in seven samples, whereas Al, Cu, and Cr exceeded limits in only two samples. The metal evaluation index (MEI), Nemerow pollution index (NI), and degree of contamination (Cd) revealed moderate to severe contamination in groundwater and unsuitability for drinking purposes. Out of the 51 analyzed samples, 48 samples exhibited potential non-carcinogenic health risks for adults, while all samples exceeded the hazard index (HI) threshold value (01) for children. Concentrations of As and Mn were identified as the main contributing factors to the higher HI values in both adults and children. However, the concentrations of Cu, Al, Cr, and B in groundwater were not individually found to be as risky. This study provided valuable insights to conduct a future comprehensive investigation of the designated region to delineate safe and hazardous zones for the installation of shallow tubewells. Furthermore, there's a need to enhance public awareness regarding the long-term ramifications of consuming contaminated water.

Rapid barrier estuary infill in a geologically-constrained setting: Aireys Inlet/Painkalac Creek, Victoria, Australia

The Holocene infill of an intermittently open-closed barrier estuary (Painkalac Creek/Aireys Inlet) was examined on the southern margins of Australia, through aerial LiDAR, coring, sedimentology, radiocarbon dating and pollen analysis. It is found that almost all the accommodation space within the estuary has been occupied, with a thick sequence (>9 m) of sediments being deposited rapidly soon after flooding by the sea. The rate of sedimentation was 4.8 mm/year which closely matches the rate of sea level rise (4.5 mm/year) during the 1200 year period that the estuary infilled, from around 8000–6800 years ago. The evidence of estuarine deposition above the elevation of the modern intertidal zone provides significant further evidence for the presence of the mid-Holocene highstand sea level in this relatively unstudied part of the Australian coast. The pattern of infill departs from the traditional barrier evolution models. The first phase of infill was likely tide dominated with subtidal sand shoals being found landward of a subtidal bedrock sill. Once a beach-barrier sequence formed, the estuary infilled in a more traditional manner, with lateral progradation of a flood tide delta and central mud basin infill. The barrier estuary of Painkalac Creek therefore has undergone a complex evolutionary history, characterised by a change in process dominance from classic tidal to wave-dominated form. Infill occurred in a keep-up (or fast catch-up) mode, with geological control occurring in regard to the presence of an intertidal bedrock sill at the mouth of the estuary.

Facies Analysis Using Attribute Seismic With Simply Rock Typing in Field “X” Kutai Basin

Abstract Field X is one of the hydrocarbons producing fields in the Kutai Basin which is one of the largest and deepest tertiary basins producing the second largest hydrocarbon production in Indonesia with 2.47MMBO oil reserves and 28.1 TCF gas. Based on qualitative analysis, the target zone in the four wells is estimated to be within the range of 1050 – 1400 ms. Sensitivity analysis was employed to determine the most sensitive parameters capable of distinguishing lithology within the formation. To ascertain the optimal number of attributes to be used, linear regression was employed, resulting in the selection of 12 attributes with a correlation coefficient of 0.919. Concurrently, log data was utilized for electro facies analysis. Electro facies analysis involved interpreting the shape of the gamma-ray curve, which indicated that the deposition setting in the four wells resembled a delta system. Additionally, rock typing was employed to classify rocks based on wet clay shale parameters, yielding information about the direction and more detailed settings of deposition. The results from the multi-attribute method, rock typing, and electro facies analysis, it was determined that Field X was deposited in a tidal delta to delta front environment, with a deposition direction from North to South.

A Novel Method for Analyzing Sandbar Distribution in Shelf-Type Tidal Deltas Using Sediment Dynamic Simulation

Shallow marine shelf sedimentation is a hot and difficult topic in today’s reservoir sedimentology research, and it is widely present in the world. The shallow marine shelf sedimentation is not only affected by complex hydrodynamic effects such as tides and waves, but also controlled by bottom tectonic features, forming a complex and varied sedimentation pattern. During the Middle Jurassic period, the northern part of West Siberian Basin was characterized by a shallow marine shelf sedimentary environment. In the central reion of this basin, a typical tectonic uplift zone developed, forming a tectonic background of “one uplift zone between two depressions”. Simultaneously, the dominant influence of tides in the shallow marine shelf environment facilitated the formation of a typical shelf-type tidal delta sedimentation system in the Jurassic strata of the northern part of West Siberian Basin. This sedimentation constitutes a significant natural gas reservoir, and it is important to investigate the sedimentary evolution of shelf-type tidal deltas and to clarify the internal structure and distribution of sedimentary sand bodies and interlayers in shelf-type tidal deltas, which is the basis for the fine development of this type of reservoir. This paper takes the Jurassic strata in the Y region of northern part of West Siberian Basin as the research object, and conducts numerical simulation based on sedimentary dynamics for the shelf-type tidal delta sedimentation formed under the tectonic background of “one uplift zone between two depressions”. In addition, tidal amplitude and initial water level were selected for different hydrodynamic factors to study the main controlling factors of shelf-type tidal delta sedimentation. The simulation results show that tidal amplitude is positively correlated with three-dimensional configuration characteristic parameters of the sedimentary sand bodies, and the development of tidal bars becomes more and more limited as the initial water level increases. This paper systematically investigates the sedimentary evolution of shelf-type tidal delta under the tectonic background of “one uplift zone between two depressions” by the sedimentary dynamics method, which deepens the understanding of the shelf-type tidal delta sedimentation process and provides a new thinking for the development of this sedimentary reservoir type (School of Geosciences China University of Petroleum (East China)).

Lithofacies, architecture and evolution of carbonate tidal delta system: Implications for reservoir heterogeneity (mid-cretaceous Mishrif Formation, Southeast Iraq)

Carbonate tidal delta system used to be put much less attention on unlike the counterparts in siliciclastic systems, and its unique architecture influences the reservoir heterogeneity and corresponding development strategy significantly. This study aims to recognize and characterize the carbonate tidal delta system of Mishrif Formation in Southeast Iraq.Based on detailed observation of cores from 5 wells and integrated analysis on well-loggings and 3D seismic, five lithofacies associations were recognized: (1) subtidal mudstone to wackestone (LF-1); (2) back-margin massive wackestone to packstone (LF-2); (3) high-energy bioclastic grainstone (LF-3); (4) swamp carbonaceous mudstone interbedded with bioclastic wackestone (LF-4); and (5) incision brown mudstone to wackestone with chert nodular (LF-5).A detailed description of the recognized lithofacies and facies association of the system is given in this work, together with an interpretation of the corresponding depositional setting. The architecture of the reservoir bodies has been reconstructed in detail and placed within a high-frequency sequence-stratigraphic framework.The studied interval belongs to the highstand system tract (HST) of a single composite sequence and comprises two shallowing-upward high-frequency sequences. The internal architecture of the tidal delta system is the result of complex tidal-dominated hydrodynamics.Facies and diagenetic partitioning with each high-frequency sequences are primary controls on pore types and reservoir properties. Original lithofacies texture and subsequent meteoric dissolution resulted in regional barriers and high permeable streaks that created a complex internal architecture of reservoir bodies. The shape of reservoir bodies generally follows those of the lithofacies, but with the addition of intercalated thin flow barriers.

Sedimentology of a delta formed by agricultural river discharge into a flood‐control reservoir, Iowa

AbstractRiver deltas are ecologically critical landscape components and are responsible as habitats for millions of people, wildlife, and plant communities. Deltas store vast quantities of eroded nutrient‐rich sediment and play a significant role in water quality management through nutrient cycling and storage. Many studies have been conducted in marine and tidal delta environments that characterize the sedimentology and geomorphic characteristics of these relatively young landscapes. However, little work has been completed in even younger inland reservoir deltas. This study characterized the sediments and geomorphology of the growing delta forming at the outlet of the Des Moines River into Red Rock Reservoir in south‐central Iowa and discussed the implications of the lower delta sediment and topographic characteristics in terms of sediment and nutrient storage, and the potential impact of the delta on other hydroecological factors. We found that the ca. 30‐year‐old lower delta is storing up to 60% of the contributing watershed's eroded sediment and total carbon, with total sediment depths of ca. 9 m across the 755‐ha area. Further, we identified two major geomorphic landscape positions within the lower delta that were categorized as distributary channels and delta plains. Sedimentological differences in these microscale landscape positions were identified. Sand content was greater at lowest distributary channel elevations and at the highest plain elevations whereas silt dominated the elevation range between these two extremes. The zone of silt accumulation corresponds to the range in elevation associated with normal lake level management. The silt‐dominated area is regularly inundated and covered with a variety of emergent vegetation and is the zone of critical importance for waterbird habitat and nutrient‐processing capacity.

Lithofacies and Sediment Sequences of a Microtidal, Wave-Dominated Tropical Estuary in Somone Lagoon (Senegal, West Africa)

Estuary sedimentary sequences have been the focus of several papers in the last decades; however, the majority these papers were centered in mesotidal and macrotidal estuaries of the middle latitudes. This present paper studies, from a sedimentological point of view, the infilling of a microtidal, wave-dominated tropical estuary, where wide tidal flats, mangroves and sabkhas are developed. Somone Lagoon is a Senegalese protected environment, very rich from an ecological point of view and with a definitive touristic vocation. For this work, 14 piston cores were studied. Additionally, the grain size, calcium carbonate and organic matter contents of 61 sediment samples vertically distributed in these cores were analyzed. The distribution of facies and the vertical sequences of sediments show the influence of the tropical seasonal fluctuations of fluvial sediment supply and evaporation processes. A high degree of bioturbation and an elevated organic content can be interpreted as the result of a high capacity of retention of the organic material into the estuary influenced by the weak tidal currents typical of a microtidal regime. These processes, acting since the last Holocene invasion of sea level, caused an advanced state of infilling of this estuarine system where both flood tidal deltas and bay head deltas prograde above the fine facies of the central domain of the estuary.

Landscape determinants of aquatic estuarine habitat use by juvenile Chinook salmon

Habitat restoration planning and design can be informed by information on spatial patterns in habitat use, which can be obtained from temporally and spatially extensive monitoring efforts. Using records from long-term monitoring in four tidal deltas, we modeled how landscape features (channel types, wetland vegetation types, and a channel network connectivity index) influenced juvenile natural-origin (NOr) and hatchery-origin (HOr) Chinook salmon presence/absence and density when present. Models detected strong effects of landscape characteristics on either presence/absence or density, although the directionality and relative importance of these features differed between NOr and HOr fish. In addition, while interannual differences were stronger for NOr juveniles, the seasonal pattern was much stronger for HOr fish and was in fact the strongest predictor of density. For both types of fish, interactions between landscape features and seasonal pattern existed, indicating that habitat use changed dynamically from the beginning to the end of the rearing period. These findings help provide general principles for prioritizing location and designing habitat restoration projects.

Sequence Stratigraphy of the Jurassic Strata and Occurrences of Potential Sandstone Reservoirs in the ST Gas Field, Northern West Siberia Basin

Jurassic strata in the ST gas field of the northern West Siberia Basin have been regarded as a potential exploration target with undiscovered hydrocarbon resources. However limited research has been performed on the sequence stratigraphy of the Jurassic strata, as well as its sandstone distribution controlled by variable sea level change and sediment input. In this paper, four third-order sequences (SQ1, SQ2, SQ3, and SQ4) and nine fourth-order sequences for the Jurassic strata are interpreted based on seismic facies analysis and the lithology stacking patterns of seven wells. SQ1 is characterized by the special Bazhenov Formation which is featured by regionally distributed deep marine shales. SQ2 (J1) is composed of a coarsening upward sequence, the base of which is an unconformable surface that can be recognizable in both seismic profiles and well logging data. SQ3 (J2-J8) is composed of a complete fining-upward and coarsening-upward sequence, showing a series of transgressive and regressive successions. A complete SQ4 has not been drilled through by all the seven wells, only showing a coarsening upward succession on its top (J9) which evolves into a fining upward succession at the base of SQ3. Combined with the seismic inversion result, which predicts sandstone distribution, a sequence evolution model was built for SQ3 showing a full unit of transgressive system tract and highstand system tract (TST-HST) which often occurs in shallow marine shelves. During sequence development, most reservoir sandstones are deposited in the shelf and tidal delta environment at the bottom of the TST and the top of HST, and mudstones are deposited as shelf mudstones, especially at maximum flooding surface. That is controlled by both accommodation and sediment input. Generally, under this sequence framework, the depositional architecture can be further analyzed with implications for source rock, reservoir sandstones, and sealing rock, which may guide future gas exploration and exploitation in this area.

MIGRATION AND WELDING OF AN ESTUARINE BARRIER-SPIT DRIVEN BY DELTA EVOLUTION AND STORMS

As sea levels rise globally in response to anthropogenic climate change, coastal depositional systems that persist in dynamic equilibrium with accommodation space, sediment supply and hydrodynamic processes may begin to respond by redistributing sediment, causing erosion or migration of landforms that may have appeared as stable over previous decades to centuries. In contrast, systems that have adjusted to inherited or changing boundary conditions over historical times offer insights on the modes and timescales of potential future change in remobilised coastal systems. We investigate the coupled evolution of an estuarine sand barrier-spit and tidal delta over the past century, focusing on storm-driven erosion and overwash during recent decades that triggered recurrent barrier migration (rollover), ultimately welding it to the bedrock valley framework. Historical aerial photographs and recent high-resolution satellite and aerial imagery are analysed to map morphological change and calculate decadal trends in shoreline and barrier migration. Ocean wave and water level conditions between image dates capturing notable responses are analysed using wave and tide records from nearby measurement stations.

Monitoring of drainage system and waterlogging area in the human-induced Ganges-Brahmaputra tidal delta plain of Bangladesh using MNDWI index

Waterlogging is one of the major global problems which affects agro-economic activities around the world. In the coastal areas of Bangladesh, especially the southwestern coast, drainage congestion and waterlogging are very common which makes the area uninhabitable. Therefore, timely checking of drainage systems and surface water, and conveying data on the dynamics of drainages and surface water are important for plan and supervisory processes. The present study took an effort to illustrate the waterlogging and morphological change of the rivers in the southwestern coast of Bangladesh through the Modification Normalized Difference Water Index (MNDWI) values which are valuable indicators for monitoring the water area and land use pattern change. Landsat images (Landsat L8 Oli TIRS, Landsat ETM+, Landsat TM) were used in the research. The study reveals that from 1989 to 2020, the shallow water area (mostly covered with rivers) decreased by ∼14.30 km2 yr−1, whereas the wet-land area (mostly covered with beels and water logging areas) increased by ∼ 67.12 km2 yr−1. The bare land area also increased at a rate of ∼ 36.90 km2 yr−1. On the other hand, the green vegetation decreased at a rate of ∼166.1 km2 yr−1, whereas the moderate green vegetation area increased by ∼ 69.77 km2 yr−1 for the same period. In the coastal zones of Bangladesh, the polders, embankments, upstream dams, etc., enhance more sedimentation within the channels rather than in the nearby tidal plains. As a result, the shallow water area which is mostly covered by rivers is gradually decreasing. Moreover, due to increase in wet-land areas with salinity intrusions which affect the vegetation. Therefore, the green vegetation area is regularly declining due to demolition or conversion to moderate green vegetation. The findings of the research will be supportive for coastal scientists worldwide, policy makers & planners, and finally supportive for sustainable management of the coastal areas including Bangladesh.

Peak Water Levels Rise Less Than Mean Sea Level in Tidal Channels Subject to Depth Convergence by Deepening

AbstractEffects of sea‐level rise (SLR) on future peak water levels in tidal deltas and estuaries are largely unknown, despite these areas being densely populated and at high risk of flooding. While the rates of SLR accelerate, many channels simultaneously experience channel deepening for navigation. With globally decreasing sediment supplies, most channels are at risk of becoming deeper when the rate of SLR accelerates and sedimentation cannot keep pace with SLR. These factors potentially favor amplification of the tides and thereby increase flood risk, but the extent to which they will do so is unknown. Here, we introduce and use a validated model for an artificially deepened multi‐branch delta to get a mechanistic understanding of non‐linear SLR‐effects on peak water levels. Results show that, when the current deepened bed level will be maintained, peak water levels do not rise on par with mean sea‐level. Thus flood risk increases less than what can be expected from the predictions of the mean sea‐level increase. The reason is that SLR causes a proportional reduction in convergence of channel area. This mechanism reduces tidal amplification. Nevertheless, SLR effects extend far beyond the range of present‐day seasonal variations, with future low water levels being equal to present‐day high water levels, while the tidal range slightly reduces. This will have consequences not only for flood risk, but also for freshwater availability, navigation and ecology.

Hydrodynamics and habitat interact to structure fish communities within terminal channels of a tidal freshwater delta

AbstractTerminal channels were historically a common feature of tidal delta ecosystems but have become increasingly rare as landscapes have been modified. Tidal hydrodynamics are a defining feature in tidal terminal channel ecosystems from which native aquatic communities have evolved. However, few studies have explored the relationship between fish community structure and hydrodynamics in these tidal terminal channel ecosystems. We sampled fish communities throughout a network of terminal channels within the northeasternmost region of the San Francisco Estuary to determine the relationship between fish community structure and hydrodynamics within these environments. We collected two years (2017 and 2018) of fish community samples using gill nets and analyzed data using multivariate community analyses and count models. We found metrics of fish diversity and counts of native fishes to be greatest upstream (farthest from tidal influence) of the tidal excursion within terminal channels. Counts of non‐native fishes were less affected by this hydrodynamic feature of terminal channels and more tightly correlated to local habitat conditions (e.g., water temperature, depth). Our results suggest that channel hydrodynamics plays a role in structuring fish communities within terminal channels, particularly native fishes. These results indicate that hydrodynamics in tidal delta ecosystems may be able to be altered in ways that benefit native fishes without the cost of water pumping.

Soil Stratum Tides

AbstractRiver deltas, where ocean tides can often freely propagate into the river, are focal points of human settlement. Beneath the delta surface, groundwater stored in the soil strata fluctuates with river tides, resulting in pressure variations within the soil strata. Here, we introduce a novel ultra‐weak fiber‐optic instrument to test the hypothesis that tide‐induced groundwater level variations induce periodic soil stratum deformation. Using borehole deployments ranging over 70 m in the subsurface of the Yangtze Delta, we observe semidiurnal and spring–neap cycles of soil stratum deformation and reveal its dependence on lithology and depth. This allows us to coin the new term “soil stratum tide,” defined as the periodic deformation of soil strata in response to pressure fluctuations induced by tides in open water. High‐accuracy monitoring of the breathing of tidal deltas enables calibrating Earth observation systems, analysis of delta subsidence, and safeguarding of infrastructure jeopardized by soil stratum deformation.

Sedimentary systems of the Oligocene Huagang Formation in the central anticline zone of the Xihu Depression, East China Sea Shelf Basin

The Xihu Depression is the largest hydrocarbon-bearing depression of the East China Sea Shelf Basin (also referred to as the ECSSB). However, the depositional systems and reservoir distribution of the Oligocene Huagang Formation in the Xihu Depression are still controversial. Under the guidance of sedimentology and stratigraphy, this study documented a marine-terrestrial transitional environment in the restricted bay setting of the Oligocene Huagang Formation through core description, well logging, and seismic data analysis. This study also revealed that the Oligocene Huagang Formation is dominated by tidal delta, estuary, and gravity flow deposits in the central anticline zone of the Xihu Depression. The new understanding of the sedimentary systems and the discovery of the transgressive gap in the eastern Diaoyu Islands uplift explain the origin of fine-grained sediments and the EW-trending sand bodies in the central depression and the sand bodies parallel to shoreline in the west slope belt, which cannot be explained by previous study results, such as southern transgression or fluvial deltas and even lacustrine deposition. Moreover, the tidal channels, tidal sand flats, and gravity flow sand bodies formed by the transgressive tides are high-quality reservoirs. The study will provide a basis for well placement and serve as guidance for the selection of favorable hydrocarbon exploration areas in the Xihu Depression.

A new interpretation for the Pliensbachian Cook Formation (northern North Sea) as north–south-prograding tidal deltas and shelf ridges in the Early Jurassic Seaway: new model of linkage to the Norwegian Sea

Abstract The Lower Jurassic Cook Formation reservoir is a hydrocarbon-prolific unit that produces from several fields in the northern North Sea. For 40 years this formation has been interpreted as a westward-prograding deltaic unit sourced from Norway. Despite numerous discoveries, exploration targeting this unit has been hampered by well failures with lack of reservoir sand, discouraging companies from further exploration of this play. During a current re-evaluation of the process sedimentology of the Norwegian offshore basins, the Cook Formation is now interpreted as the middle to distal reaches of a very large, north-to-south-oriented delta system, variably confined within the Early Jurassic Seaway running from the Norwegian Sea into the northern North Sea. The Cook Formation is a subaqueous delta built southward during regression, whereas several internal transgressive phases produced sands that were reworked as north–south-oriented, shelf tidal ridges. The tidal ridges of the Cook Formation constitute some of the best reservoirs and are elongated with stacked, well-sorted, cross-bedded sandstone sets with mudstone drapes. Both the elongate tidal sand-ridges and intervening mudstone-rich, inter-ridge zones are proven by numerous well observations and illustrated by seismic amplitudes. In contrast to earlier eastern derivation models, these new results for the depositional system of the Cook Formation better explain the Cook well successes and failures in the northern North Sea. This work also strongly suggests that the tide-dominated subaqueous delta to transgressive-ridge system of the Cook Formation is spatially linked with the time-equivalent shorelines, subaerial tidal deltas and estuaries of the Tilje Formation in the Haltenbanken region to the north. The Tilje Formation deltas built into the Early Jurassic Seaway due to rift-initiation and rift-shoulder uplift, drained southwards and spilled eventually into the northern North Sea, becoming the entirely subaqueous Cook Formation. The relatively narrow seaway enhanced the tidal currents and suppressed wave activity, resulting in Cook subaqueous delta lobes and ridges without any delta-top facies. Overall, this elongate and extensive, Pliensbachian deltaic to estuarine system of the Early Jurassic Seaway off Norway competes in scale with some of Earth's largest present-day deltas.

Estimation of bedload sedimentation rate in a paleo-drowned river-valley

Extensive, high-resolution seismic data were correlated with borehole, land use, and geological data to calculate the mass of genetically different sediment deposits in the Middle Harbour estuary in Sydney, Australia. Middle Harbour is a drowned-river valley located adjacent to the larger Sydney estuary. The estuary follows a well-defined sedimentation model featuring small fluvial bedload delta deposits in the upper reaches of the embayments, a deep, central extensive mud basin overlying transgressive basal accumulations and a large flood-tide delta at the entrance. Deposits of an estimated 5094 t of bedload, 21,143 t of suspended sediment and 5947 t of transgressive basal material located in the estuary provided average sediment accumulation rates of 0.68 t year−1, 1.29 t year−1, and 2.86 t year−1, respectively. These rates, determined from measured accumulations, were surprisingly low and substantially smaller than modelled rates. However, low sediment accumulation rates for suspended material may be due to fine sediment escaping over the top of the marine tidal delta, which effectively traps all bedload material from exiting the Harbour. Results of this study indicate that Holocene bedload sedimentation in Middle Harbour was slow and regular until a rapid increase after urbanisation commenced in the catchment. Most pre-Holocene material was eroded from Middle Harbour during the Last Glacial period with sediment currently present in the estuary having been deposited since sea-level recovery.

Haulover sandbar dredging controversy

Bakers Haulover Inlet in Miami-Dade County, Florida, is an important waterway for recreational boaters connecting Biscayne Bay to the Atlantic Ocean. The dredging of the Haulover sandbar (properly termed the flood tidal delta) by the U.S. Army Corps of Engineers is very controversial because it has become a major attraction for boaters. This narrow inlet was artificially created for non-commercial watercraft in 1925 to provide access to the Atlantic Ocean, but it also helps promote flushing of Biscayne Bay, which is presently having pollutant problems. Maintenance dredging has occurred every three to five years since the 1960s, with the last project completed in 2017. The Corps of Engineers is providing 100% funding of the forthcoming dredging project in order to provide maintenance of the Atlantic Intracoastal Waterway and beach nourishment for the downdrift beach of Bal Harbour. Haulover sandbar parties are advertised by Trip Advisor among others as a Miami hot spot for outdoor recreation, drawing hundreds of boats and thousands of people during low tide, especially during the weekend.

НЕРЕШЕННЫЕ ЗАДАЧИ ИССЛЕДОВАНИЯ УСТЬЕВОЙ ОБЛАСТИ СЕВЕРНОЙ ДВИНЫ

The Severnaya Dvina River mouth is one of the most studied water objects in Russia. However, many problems still remain insufficiently understood and covered in the scientific literature, due to the exceptional complexity of natural processes that occur in branched tidal deltas. The authors systematize the problems that need to be solved and propose ways to implement. Environmental monitoring is singled out as a separate problem. It is concluded that it is necessary to develop an interdepartmental research program for the entire estuary region.

Sediment Transport Patterns of Channels on Tidal Lowland

Many reclaimed areas in Indonesia have abandoned swampland or idle land which is attributed to various factors. One of the main factors is the unsuitability of the exiting flow system in this area since the condition of the canals and water structures in this area has not been rehabilitated for a long time. No study has been carried out to investigate the suitable model for simulating the appropriate criteria for assessment of erosion within the channel on Tidal lowland in Indonesia. This study focuses on the investigation of erosion occurring within the Rural Channel and Main Drainage Channel on Tidal lowland in Palembang, Indonesia which becomes the originality of this manuscript. The erosion was attributed to the accumulation of sediment transport within the channel of the reclaimed tidal delta region Telang I. The results of the research on the P8-13S scheme show that equilibrium on the accumulation of sediment transport in the channel was observed in the Rural Channel and Main Drainage Channel on average ranging from 3,301,859 m3 to 3,349,103 m3 while the average sedimentation ranged from 809,232–898,467 m3. This study is very important in minimizing the possible erosion near riverbank.