A slough (/sluː/ ⓘ[1][2] or /slaʊ/ ⓘ)[1][2][3] is a wetland, usually a swamp or shallow lake, often a backwater to a larger body of water.[4] Water tends to be stagnant or may flow slowly on a seasonal basis.[5]
In North America, "slough" may refer to a side-channel from or feeding a river, or an inlet or natural channel only sporadically filled with water.[3] An example of this is Finn Slough on the Fraser River, whose lower reaches have dozens of notable sloughs. Some sloughs, like Elkhorn Slough, used to be mouths of rivers, but have become stagnant because tectonic activity cut off the river's source.
In the Sacramento River, Steamboat Slough was an alternate branch of the river, a preferred shortcut route for steamboats passing between Sacramento and San Francisco. Georgiana Slough was a steamboat route through the Sacramento–San Joaquin River Delta, from the Sacramento River to the San Joaquin River and Stockton.
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Everglades Perspectives: Hydrology Technician
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Hydrology Applications with LiDAR: A Case Study from Turnhole Bend
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Waterways Episode 204: Banding Migratory Hawks and Tagging Bull Sharks
Transcription
( 'Invisible Wings' song ) ( frogs calling ) ( thunder ) ( airboat noise ) ( 'This' song ) ( airboat noise ) ( underwater bubbling and airboat noise ) Fabian: The water is pretty high. It is kind of average for this time of year, average level. I am basically at the ground level for upkeeping the hydrology network in the park. We take field measurements to support the measurements taken by these sensors out here in the marsh. Which would be comprised of Shark Slough, Taylor Slough, and other surrounding areas. There is probably about 60 of these stations taking physical parameters like stage, water level, rain fall. Here, we have got the difference between surface and bottom temperature. Basically, if you could imagine, we are able to generate a profile of the hydrology here in the park. We have come a long way in data sharing with lots of other agencies. Ahhh, there is a frog in there! People from lots of other agencies have access to our data. In some cases on a daily basis. Chiefly among them would be Army Corps of Engineer and South Florida Water Management District. Their concern is in operations. Those two agencies operate a lot of the water control structures that deliver water into the park. We also have park biologists who have interest in water data and drawing insights on water conditions and how it relates to resource management concerns. I have not seen one mosquito today. That is one of the things that I like about being in the middle of the slough. It is nice and sunny. There are plenty of fish to eat the mosquito larvae. There are good field conditions out here. ( loud airboat noise ) ( helicopter noise ) Right now, we are in early May. This is the peak of the dry season, sooo. At this time of the year, we have to get to these remote sites by helicopter. Which is quite a costly way to access these sites. And then, once the waters recharge in the park, then our main way of access is by airboat. This is a deep wilderness part of the park. We are about thirty miles away from the nearest road. The helicopter is a very different experience from the airboat. Both have their merits. In the helicopter, you get a more panoramic view, a real landscape perspective. But, traveling by airboat is really nice because you get to feel more immersed. Although these datas are transmitted everyday via either radio telemetry or satellite, it is still necessary to come out here, verify that the sensors are accurately measuring. And also, clean them from the elements. One of my favorite aerial views is coming across the transition area of the freshwater grassy slough into the coastal rivers on the west side. These are mangrove lined tidal creeks that are tributaries that flow into Shark River. We are actually near the end of the Everglades watershed where it is beginning to mingle with the coastal area of the Gulf Coast. We measure several parameters. Water level is one of them. Right now, it is the depths of the dry season. So, at most of the sites that we will be looking at today, it will be below the surface of the ground. This is particularly important this time of the year to inventory our baseline water level before the rainy season hits. There was only less than an inch of rain over this period of time. We have been experiencing a below average rainfall for this dry season. ( helicopter noise ) It is very stark to see how important these residual water holes are for wildlife. It is very distinct seeing the animal tracks to and from these water reservoirs. A lot of these monitoring sites happen to be colocated in these deeper holes... which in the dry season are particularly favored by alligators and other wildlife. ( loud clicks ) Rain is collected into this funnel. It seeps down into these receptacles. And, the way it is calibrated is 1/100th of an inch of rain will cause it to tip. As it tips, this bar passes over this magnet which closes a circuit and the data logger will record that one tip as 1/100th of an inch of rain. ( water pouring ) Yeah, I like my job. I have been working here for over six years. I grew up in the south Florida area, studied environmental studies. And, took a particular concern to issues on the Everglades which are very water-related. And, it was kind of a natural path for me to follow. Half of my job consists of field work and the other half... I am at my office reviewing data, making reports, running the numbers. ( water pouring ) Oh look, I dumped it on top of a baby gator. I have seen a good amount of wildlife at this particular site. Alligators, night herons, soft-shelled turtles, Anhingas. So far today, we have seen a mother and two baby gators. There is probably more... Oh, there is a third right there. ( 'Stone Flower' song ) The Everglades is really distinguished by a dualistic climate. A really distinct dry season and a monsoon-like wet season. About 80% of the annual rainfall falls between a six-month period. This creates a really harsh dynamic of which a lot of the flora and fauna are well-adapted to. So, looking out at this prairie, it looks like vast wilderness. Uninterrupted, undisturbed, left to work out its natural processes. But, in reality, it is a very closely managed system. It is closely managed by canals, pumps, levees and other water control structures, mainly located on the periphery of the park boundary. Hold on a second... ( clicking ) Did you see the frog? ( laughs )
Plants and animals
A slough, also called a tidal channel, is a channel in a wetland.[6] Typically, it is either stagnant or slow flowing on a seasonal basis.
Vegetation patterns in a slough are largely determined by depth, distribution, and duration in the environment. Moreover, these same variables also influence the distribution, abundance, reproduction, and seasonal movements of aquatic and terrestrial life within the sloughs.[7] Sloughs support a wide variety of plant life that is adapted to rapidly changing physical conditions such as salinity, oxygen levels and depth.[8]
In general, sloughs are microhabitats high in species diversity. Open water sloughs are characterized by submerged and floating vegetation which includes periphyton mats dominated by sawgrass typically. The topographical and vegetation heterogeneity of ridge and slough landscape influences the productivity and diversity of birds and fish adapted to that wetland.[9]
Fish that typically inhabit sloughs include tidewater goby, California killifish, mosquitofish, and topsmelt.[10] Food habits of fish within sloughs consist of preying upon invertebrates; mostly epifaunal crustacean followed by epifaunal and infaunal worms and mollusks. Fish can feed on zooplankton and plant material. Research on prey species for fish in sloughs found that in a study done on Elkhorn Slough in California the mean prey richness for fish was greatest near the ocean and lowest inshore. This allows for a higher availability of food to enhance the function of inshore habitats and emphasizes the importance of invertebrate prey populations and how they influence plant production.[11]
Birds also inhabit sloughs, making them hotspots for birdwatching, with the Elkhorn Slough being one of the premier birdwatching sites in the western United States. Over 340 species have been seen visiting, including several rare and endangered species. Bird species seen in sloughs include acorn woodpecker, brown pelican, Caspian tern, great blue heron, great egret, great horned owl, snowy plover, and white-tailed kite.[12]
Sloughs are largely influenced by human development such as urban and agricultural expansion, industrial and agricultural practices, water management practices, and humans influence on species composition. Uses of identifying these aspects of human involvement can help to better predict restoration efforts to be made in managing sloughs. Examples of attributes that are affected by human stress upon the environment include periphyton, marsh plant communities, tree islands, alligators, wading birds, and marsh fishes, invertebrates, and herpetofauna.[7]
Formation
A slough can form when a meander gets cut off from the main river channel creating an oxbow lake that accumulates with fine overbank sediment and organic material such as peat. This creates a wetland or swamp environment. One end of the oxbow configuration then continues to receive flow from the main channel, creating a slough.[13]
Sloughs are typically associated with the ridge formations found in their presence. Such a landscape consists of mosaic linear ridges, typically of some sort of grass such as sawgrass ridges in the Florida Everglades, that are separated by deeper water sloughs.[11]
Edges of sloughs are layers of sediment deposited by a river over time.[6] The development of this landscape is thought to occur by the preferential formation of peat in bedrock depressions. Multiple of these deposits mounted on top of the surrounding bedrock can become elongated alongside the slough and create flow diversions within the system. Different rates of this peat accumulation could be triggered by variations in microtopography that alter plant production and vegetation type. Water flow might be the key to preventing an accumulation of organic sediment in sloughs due to the fact that accumulation leads to lowering water depths and instead allows for the growth of vegetation.[9]
Degradation
Overall little quantitative data on the degradation of slough landscape exists. Slough and ridge landscape has been greatly degraded in terms of both topographic and vegetation changes over time. Topographical changes create an increase in the relief between ridge crests and slough bottoms. Vegetation changes consist of an increase in the amount of dense grass and decrease in the area of open water, creating a blurring of the directional ridge and slough pattern.[9]
Historical everglade and slough landscape has been greatly affected and degraded by human activity. Open water sloughs support important ecological functions that have been seen to be sensitive to hydrologic and water quality problems stemmed from human activities.[14]
Restoration
Sloughs are ecologically important as they are a part of an endangered environment: wetlands. They act as a buffer from land to sea and act as an active part of the estuary system where freshwater flows from creeks and runoff from the land mix with salty ocean water transported by tides. Restoration is a big effort in California wetlands to restore slough and ridge landscapes. Examples of restoration projects on slough landscapes include The Elkhorn Slough Tidal Wetland Project,[15] Dutch Slough Tidal Restoration Project,[16] and the McDaniel Slough wetland enhancement project.[17][18]
See also
References
- ^ a b Merriam-Webster, Merriam-Webster's Unabridged Dictionary, Merriam-Webster.
- ^ a b Houghton Mifflin Harcourt, The American Heritage Dictionary of the English Language, Houghton Mifflin Harcourt.
- ^ a b "Slough - definition of slough in English". Oxford University Press. Archived from the original on October 5, 2018. Retrieved 15 May 2017.
- ^ "What is a slough?". National Ocean Service. 4 February 2016. Retrieved 15 May 2017.
- ^ Aber, James S. (2012). "Wetland Definitions and Classification". Wetland Environments. Emporia State University. Retrieved 5 May 2017.
- ^ a b Deborah Reid Harden (2004). California Geology (2nd ed.). Upper Saddle River, New Jersey: Prentice Hall. pp. 369–371. ISBN 978-0-13-100218-0. Retrieved 15 May 2017.
- ^ a b Ogden, John C. (December 2005). "Everglades ridge and slough conceptual ecological model". Wetlands. Society of Wetland Scientists. 25 (4): 810–820. doi:10.1672/0277-5212(2005)025[0810:erasce]2.0.co;2. S2CID 24622594.
- ^ "Devereux Slough - Coal Oil Point Reserve". University of California Natural Reserve System. Retrieved 15 May 2017.
- ^ a b c National Research Council; Committee on Restoration of the Greater Everglades Ecosystem; Water Science and Technology Board (25 July 2003). Does Water Flow Influence Everglades Landscape Patterns?. National Academies Press. ISBN 978-0-309-08963-0. Retrieved 15 May 2017.
- ^ "Habitat Restoration Projects". Coal Oil Point Reserve. University of California Natural Reserve System. 2017. Retrieved 15 May 2017.
- ^ a b Bernhardt, Christopher E.; Willard, Debra A. (1 October 2009). "Response of the Everglades ridge and slough landscape to climate variability and 20th-century water management". Ecological Applications. Ecological Society of America. 19 (7): 1723–1738. doi:10.1890/08-0779.1. PMID 19831066.
- ^ Elkhorn Slough Foundation. "Elkhorn Slough Birds". Retrieved 15 May 2017.
- ^ Mount, Jeffrey F. (8 November 1995). California Rivers and Streams: The Conflict Between Fluvial Process and Land Use. Berkeley: University of California Press. p. 66. ISBN 978-0-520-91693-7. Retrieved 15 May 2017.
- ^ McCormick, Paul V.; Newman, Susan; Vilchek, Les W. (14 November 2008). "Landscape responses to wetland eutrophication: loss of slough habitat in the Florida Everglades, USA". Hydrobiologia. 621 (1): 105–114. doi:10.1007/s10750-008-9635-2. S2CID 10026000.
- ^ Elkhorn Slough Foundation. "Elkhorn Slough Tidal Wetland Project: Restoration Projects". Retrieved 15 May 2017.
- ^ "Dutch Slough Tidal Restoration". California Department of Water Resources. 7 February 2017. Retrieved 15 May 2017.
- ^ "McDaniel Slough Project". City of Arcata. Retrieved 15 May 2017.
- ^ "McDaniel Slough wetland enhancement project". Appropedia. 19 November 2016. Retrieved 15 May 2017.
This page was last edited on 31 December 2023, at 17:29