Estuaries and Coastal Modeling Week 13 PDF

Estuaries and Coastal Modeling Week 13 What is an estuary? An estuary is a partially enclosed, coastal water body where freshwater from rivers and streams mixes with salt water from the ocean. Estuaries, and their surrounding lands, are places of transition from land to...

Estuaries and Coastal Modeling Week 13 What is an estuary? An estuary is a partially enclosed, coastal water body where freshwater from rivers and streams mixes with salt water from the ocean. Estuaries, and their surrounding lands, are places of transition from land to sea. USEPA website. https://youtu.be/XLumS N4G5P4 Characteristics of Estuaries The sheltered waters of estuaries also support unique communities of plants and animals specially adapted for life at the margin of the sea. Many different habitat types are found in and around estuaries, including shallow open waters, freshwater and saltwater marshes, swamps, sandy beaches, mud and sand flats, rocky shores, oyster reefs, mangrove forests, river deltas, tidal pools and seagrass beds.  Fisheries production and coastal nutrient enrichment, supplied via rivers and estuaries, have been shown to be positively correlated within many coastal systems around the world (Nixon et al., 1986; Bianchi, 2007). Why are estuaries important? They are critical natural habitats. Thousands of species of birds, mammals, fish and other wildlife depend on estuarine habitats as places to live, feed and reproduce. And many marine organisms, including most commercially-important species of fish, depend on estuaries at some point during their development. Estuaries have economic value economic benefits for tourism, fisheries and recreational activities. The protected coastal waters of estuaries also support important public infrastructure, serving as harbors and ports vital for shipping and transportation. Estuaries provide environmental services Estuaries also perform other valuable services. Water draining from uplands carries sediments, nutrients and other pollutants to estuaries. As the water flows through wetlands such as swamps and salt marshes, much of the sediments and pollutants are filtered out. This filtration process creates cleaner and clearer water, which benefits both people and marine life. Salt marsh grasses and other estuarine plants also help prevent erosion and stabilize shorelines. Act as a Protective Buffers Wetland plants and soils also act as natural buffers between the land and ocean, absorbing flood waters and dissipating storm surges. This protects upland habitat as well as valuable real estate from storm and flood damage. How are estuaries threatened? fertilizers or pet waste that wash off lawns; untreated sewage from failing septic tanks; wastewater discharges from industrial facilities; sediment from construction sites; and runoff from impervious surfaces like parking lots. Estuarine Morphology (Nature.com) For more details on Estuary formation? Read the following link: https://www.nature.com/scitable/knowledge/library/ estuaries-where-the-river-meets-the-sea-102734157/ Test your understanding: Review Question Explain with the help of an annotated diagram on the morphology of an estuary and how anthropogenic activities can impact it. Estuarine characteristics & hydrodynamics. The primary factors controlling estuarine hydrodynamic processes are tides and other forcings from open boundaries, freshwater inflows, wind, evaporation/precipitation, and heatflux exchanges with the atmosphere, and geometry and topography of the estuary. Estuarine characteristics Salinity: Salinity is a measure of salt concentration in water: Higher salinity means more dissolved salts Water density increases with increasing salinity and decreasing temperature. This relationship explains why water of low salinity tends to float above denser water that is colder and of higher salinity. In terms of density variation, increasing 1 ppt of salinity is approximately equal to decreasing 4 °C of water temperature. Therefore, salinity variation often changes estuarine stratification more effectively than temperature variation.  Estuarine Circulation Sketch of estuarine circulation Stratification in Estuaries Highly stratified estuaries They have the following characteristics: (1) flow ratio: >1.0, (2) salinity difference: large, and (3) vertical entrainment: strong. In these estuaries, river flow dominates tidal motion and controls the circulation pattern. Moderately stratified estuary They have the following characteristics: (1) flow ratio: 0.01, (2) salinity difference: moderate, and (3) vertical entrainment: moderate. Moderately stratified estuaries are between highly stratified and vertically mixed estuaries. Strong tidal flows and large river discharge result in both turbulent mixing and entrainment. This mixing leads to vertical exchanges between the two layers in both directions. the salinity varies continuously through the water column, without a distinct Vertically mixed estuary They have the following characteristics: (1) flow ratio: