An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environments and are an example of an ecotone. Estuaries are subject both to marine influences such as tides, waves, and the influx of saline water, and to fluvial influences such as flows of freshwater and sediment. The mixing of seawater and freshwater provides high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world.
Wetlands, or simply a wetland, is a distinct ecosystem that is flooded or saturated by water, either permanently or seasonally. Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The primary factor that distinguishes wetlands from terrestrial land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique anoxic hydric soils. Wetlands are considered among the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal species. Methods for assessing wetland functions, wetland ecological health, and general wetland condition have been developed for many regions of the world. These methods have contributed to wetland conservation partly by raising public awareness of the functions some wetlands provide. Constructed wetlands are designed and built to treat municipal and industrial wastewater as well as to divert stormwater runoff. Constructed wetlands may also play a role in water-sensitive urban design.
A river delta is a landform shaped like a triangle, created by the deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs at a river mouth, when it enters an ocean, sea, estuary, lake, reservoir, or another river that cannot carry away the supplied sediment. It is so named because its triangle shape resembles the uppercase Greek letter delta, Δ. The size and shape of a delta are controlled by the balance between watershed processes that supply sediment, and receiving basin processes that redistribute, sequester, and export that sediment. The size, geometry, and location of the receiving basin also plays an important role in delta evolution.
A marsh is — according to ecological definitions — a wetland that is dominated by herbaceous rather than woody plant species. More in general, the word can be used for any low-lying and seasonally waterlogged terrain. In Europe and in agricultural literature low-lying meadows that require draining and embanked polderlands are also referred to as marshes or marshland.
A salt marsh, saltmarsh or salting, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is dominated by dense stands of salt-tolerant plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh in trapping and binding sediments. Salt marshes play a large role in the aquatic food web and the delivery of nutrients to coastal waters. They also support terrestrial animals and provide coastal protection.
A tidal marsh is a marsh found along rivers, coasts and estuaries which floods and drains by the tidal movement of the adjacent estuary, sea or ocean. Tidal marshes experience many overlapping persistent cycles, including diurnal and semi-diurnal tides, day-night temperature fluctuations, spring-neap tides, seasonal vegetation growth and decay, upland runoff, decadal climate variations, and centennial to millennial trends in sea level and climate.
An aquatic ecosystem is an ecosystem found in and around a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms—aquatic life—that are dependent on each other and on their environment. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems. Freshwater ecosystems may be lentic ; lotic ; and wetlands.
Located in northern California, the Suisun Marsh has been referred to as the largest brackish water marsh on west coast of the United States of America. The marsh land is part of a tidal estuary, and subject to tidal ebb and flood. The marsh is home to many species of birds and other wildlife, and is formed by the confluence of the Sacramento and San Joaquin rivers between Martinez and Suisun City, California and several other smaller, local watersheds. Adjacent to Suisun Bay, the marsh is immediately west of the legally defined Sacramento-San Joaquin Delta as well as part of the San Francisco Bay estuary.
A tidal river is a river whose flow and level are caused by tides. A section of a larger river affected by the tides is a tidal reach, but it may sometimes be considered a tidal river if it had been given a separate and another title name.
Brackish marshes develop from salt marshes where a significant freshwater influx dilutes the seawater to brackish levels of salinity. This commonly happens upstream from salt marshes by estuaries of coastal rivers or near the mouths of coastal rivers with heavy freshwater discharges in the conditions of low tidal ranges.
A mouth bar is an element of a deltaic system, which refers to the typically mid-channel deposition of the sediment transported by the river channel at the river mouth.
A tidal prism is the volume of water in an estuary or inlet between mean high tide and mean low tide, or the volume of water leaving an estuary at ebb tide.
Estuarine water circulation is controlled by the inflow of rivers, the tides, rainfall and evaporation, the wind, and other oceanic events such as an upwelling, an eddy, and storms. Estuarine water circulation patterns are influenced by vertical mixing and stratification, and can affect residence time and exposure time.
High marsh is a tidal marsh zone located above the Mean Highwater Mark (MHW) which, in contrast to the low marsh zone, is inundated infrequently during periods of extreme high tide and storm surge associated with coastal storms. This zone is impacted by spring tides, which is a bi-monthly lunar occurrence where the high marsh experiences higher inundation levels. The high marsh is the intermittent zone between the low marsh and the uplands, an entirely terrestrial area rarely flooded during events of extreme tidal action caused by severe coastal storms. The high marsh is distinguished from the low marsh by its sandy soil and higher elevation. The elevation of the high marsh allows this zone to be covered by the high tide for no more than an hour a day. With the soil exposed to air for long periods of time, evaporation occurs, leading to high salinity levels, up to four times that of sea water. Areas of extremely high salinity prohibit plant growth altogether. These barren sandy areas are known as "salt pans". Some cordgrass plants do survive here, but are stunted and do not reach their full size.
Low marsh is a tidal marsh zone located below the Mean Highwater Mark (MHM). Based on elevation, frequency of submersion, soil characteristics, vegetation, microbial community, and other metrics, salt marshes can be divided to into three distinct areas: low marsh, middle marsh/high marsh, and the upland zone. Low marsh is characterized as being flooded daily with each high tide, while remaining exposed during low tides.
Ennore Creek is a backwater located in Ennore, Chennai along the Coromandel Coast of the Bay of Bengal. It is located in the zone comprising lagoons with salt marshes and backwaters, submerged under water during high tide and forming an arm of the sea with the opening to the Bay of Bengal at the creek. The zone is spread over an area of 4 km2, and the creek covers an area of 2.25 km2. It is located 20 km north of the city centre and 2.6 km south of the Ennore Port, and the creek area stretches 3 km into the sea and 5 km along the coast. The creek is nearly 400 m wide, elongated in northeast–southwest direction and merging with the backwater bodies. Once a flourishing mangrove swamp, the creek has been degraded to patches in the fringes mainly due to human activities in the region. The depth of the creek varies from 1 to 2 m and is shallow near the mouth. The north–south trending channels of the creek connect it with the Pulicat Lake to the north and to the distributaries of the Kosasthalaiyar River in the south. The northwestern part of the creek merges with the tidal flats. The soil in the region is of loamy and alluvial types. Most of the area consists of tracts of alluvial soil and the eastern region comprises beach dunes, tidal flats and creek. The creek is oriented from west to east and opens into the Bay of Bengal to the east at Ennore. The creek acts as an outlet for the excess water from the Poondi reservoir. The creek separates the town of Ennore from the Ennore Port located in the north and the Kattupalli Shipyard located further north. The North Chennai Thermal Power Station is located at the north of the creek and the Ennore Thermal Power Station is located to the south. The creek is part of the Pulicat water system, including the Pulicat lagoon and the Buckingham Canal. As per the 1991 Coastal Regulation Zone notification, the entire Pulicat water system is designated CRZ I. The creek is experiencing siltation due to emergence of the Ennore Port.
A slough is a wetland, usually a swamp or shallow lake, often a backwater to a larger body of water. Water tends to be stagnant or may flow slowly on a seasonal basis.
Rincon Bayou is in the Nueces River delta, and located northwest of Corpus Christi. The Rincon Bayou is subject to freshwater inundation following seasonal rainfall events farther inland along the Nueces River. The freshwater inundation provides the bayou with nutrients and enough fresh water to remove the saline water from the estuarine system. In 1984, though, the United States Bureau of Reclamation built a dam along the Frio River to create Choke Canyon Reservoir, which has consequently caused a decrease in freshwater flow into the Rincon Bayou. This decrease has affected the wetland plant and macroinvertebrate communities. The hypersaline condition makes it difficult for plants to produce seeds and for the seeds to germinate. As part of an effort for the Rincon Bayou–Nueces Marsh Wetlands Restoration and Enhancement Project, the Bureau of Reclamation has created a channel between the Nueces River and the Rincon Bayou. It is located just east of US 77 and extends 900 ft to the bayou. The purpose of the channel is to increase the freshwater inflow into the bayou. A second channel was cut within the bayou in an effort to increase the freshwater flow to an area dominated by sand and mud flats. The increase in freshwater flow should help re-establish the vegetative community.
Coastal erosion in Louisiana is the process of steady depletion of wetlands along the state's coastline in marshes, swamps, and barrier islands, particularly affecting the alluvial basin surrounding the mouth of the Mississippi River. In the last century, Southeast Louisiana has lost a large portion of its wetlands and is expected to lose more in the coming years, with some estimates claiming wetland losses equivalent to up to one football field per hour. One consequence of coastal erosion is an increased vulnerability to hurricane storm surges, which affects the New Orleans metropolitan area and other communities in the region. The state has outlined a comprehensive master plan for coastal restoration and has begun to implement various restoration projects such as fresh water diversions, but certain zones will have to be prioritized and targeted for restoration efforts, as it is unlikely that all depleted wetlands can be rehabilitated.
Sedimentation enhancing strategies are environmental management projects aiming to restore and facilitate land-building processes in deltas. Sediment availability and deposition are important because deltas naturally subside and therefore need sediment accumulation to maintain their elevation, particularly considering increasing rates of sea-level rise. Sedimentation enhancing strategies aim to increase sedimentation on the delta plain primarily by restoring the exchange of water and sediments between rivers and low-lying delta plains. Sedimentation enhancing strategies can be applied to encourage land elevation gain to offset sea-level rise. Interest in sedimentation enhancing strategies has recently increased due to their ability to raise land elevation, which is important for the long-term sustainability of deltas.
