Massive Expansion Of The River Mouth Delta

In the lower reaches, it flows through the North China Plain, ending at the delta of Bohai Sea. In this section, excessive sediment deposits raise the riverbed several meters over the surrounding grounds.

In 1992, The Elwha River Ecosystem and Fisheries Restoration Act of 1992 authorized the US Federal Government to acquire the hydroelectric power projects of Elwha Dam and Glines Canyon Dam, where are located on the Washington State for demolition for habitat restoration and decommissioning. The dam removals began in 2011 and finished in 2014. I wondering that why government decided to remove the dam and what happens in Elwha River after dam removal. In this paper, I write about the following topics: main purpose of the Elwha and Gliens Canyon dam, effects to the Elwha River as well as ecosystem after constructing dam, reasons of the dam removal, process of the dam removal, and effects after dam removal.

The levee system has disrupted the natural deposits that are left from the overflow of the river.2

Dams have arguably put the largest strain on the Chinook salmon. In Columbia River Basin of the Pacific Northwest alone, over 55% of historical spawning habitat has been blocked off by dams (Harrison, 2008) Damn also cause rivers to slow down which in turn causes them to become warmer. This makes for a less ideal habitat for the salmon, and more ideal circumstances for the predators of the salmon. The slowing of a river can also be cause for disease( U.S.F.W.S). Also only about 1% of present

In the article “Changes at Snake River dams helping Idaho sockeye salmon” it states that “an unusual combination of low water and an extended heat wave pushed water temperatures past 70 degrees, lethal for cold-water sockeye.” I have a very strong connection to fishing and I hate it when fish die for no good reason or because of a manmade structure. A report by the National Oceanic and Atmospheric Administration said “One of the factors contributing to the deaths of sockeye salmon was “fallback,” a tendency of fish to successfully climb a dam’s fish ladder but then, running into warm water, decide to go back downstream, often via a dam’s spillway or through the turbines.” This reminds me of the time I was fishing near a small dam and caught

Aquatic biologists from the Cape Cod National Seashore have published newsletters stating that “increased intertidal volume produces greatly increased tidal flushing. Better flushing will reduce floodwater mosquito breeding on the wetland surface, dilute the presently high fecal coliform counts that have closed river-mouth shellfish beds, and improve water-column aeration by flooding the wetland twice each day with oxygen-rich Cape Cod Bay water” (CCNS, 2011). After the restoration begins taking place and the water levels are allowed to rise, the greater amounts of water will impact where they once dominated in the wetland soils that have fallen to being drained by the dike. This will, in turn, offset the chemical effects of the dam that caused acidity issues and toxic metal presence which has killed off fish populations in adjacent effected waterways (Portnoy and Giblin,

All of the 3,350 miles of riverine habitat within the pallid sturgeon's range have been affected by man. Approximately 28% has been impounded, which has created unsuitable lake-like habitat; 51% has been channelized into deep, uniform channels; the remaining 21% is downstream of dams which have altered the river's hydrograph, temperature and turbidity. Commercial fishing and environmental contaminants may have also played a role in the pallid sturgeon's decline. The resultant changes to the Missouri River in the upper Great Plains from channelization prevent upstream migration. The reduced water flow rates and sediment loads have brought an end to the seasonal flooding of the flood plains in the region.

National Geographic’s American science journalist, Michelle Nijhuis published an article on August 27th, 2014 discussing the process of the removal of the Glines Canyon Dam on the Elwha River in Washington State. The removal of the Glines Canyon dam is the largest dam removal that has ever taken place thus far. The removal of the dam began in late 2011, 3 years later after the removal of the dam was complete the salmon began again migrating down river, trees and vegetation began to sprout in the reservoir bed, and sediment that was once trapped behind the dams walls are now rebuilding beaches at Elwha’s outlet to the sea. In the last 5 miles of the 45 mile Elwha river, where Olympic National Park now lies, the salmon run were world famous and

Intertidal (mud) flats are shielded intertidal and shallow sub tidal areas (Quinn, 2014), with significant ecosystems that provide a diversity of highly productive, environmental habitats that are essential sources of food for fish during times of high tide, and for birds in low tide. The sediment composition of intertidal flats depends on the “interactions between the physical, chemical and biological processes” (Widdows, et al., 2004), but the sediment if mainly fine particles and mostly muds. The sediment itself can also either have vegetation growth or be a completely bare flat region. (Quinn, 2014).

In the upper corer of the topo map, it shows the same feature that was observed in figure 6, figure 7 and figure 8, where the ancient shoreline of the Salton Sea once resided. Southwest of the topo map is shows contours lines evenly space-out and directional flow of small channels which is evident of flash flooding. So, that area is a flood plain or a sheet flow that has eroded the base of the alluvial fan. The alluvial fan is very distinctive in the topo map where the active channel flows downstream through a laterally confined mountainous valley that cuts through the alluvial fan, ancient shoreline and bleeds to a non-confined lowland of the flood

In Phase 1 dredging of the Hudson River, the idea was to take the amount of polychlorinated biphenyl (PCB’s) from the sediment in the river bottom, but do to the method that was being used, clamshell dredge buckets, the material transported downstream, which lead to Phase 2. For Phase 2 the EPA recommended the use of coffer damming, vacuum dredging

Shoreline erosion is a natural process that takes place on lakes, streams, waterways and along the coast. It is the progressive, albeit

The longshore drift shapes the coastline by carrying sand from sites of high wave activity to those of low wave activity. The volume of sand carried away from or delivered to different points along the coast can be as much as 2,000 cubic meters per day (71,000 cubic feet), enough sand to fill an Olympic-sized swimming pool (Nepf).

The man-made sea created by the dam would submerge important archaeological sites, some dating as far back as the Paleolithic Age. Thousands of invaluable relics, ancient burial sites, 200,00 year old fossils, and new information of a little known, obscure people known as the Ba will be lost (Topping, 1996). Even though $37.5 million has been "earmarked for the rescue of archaeological sites threatened by the dam's construction" (Childs-Johnson, 1996), only "ten to twenty percent of these treasures could be saved." (Topping, 1996). Estimates range from $180 million to $360 million to save ten percent of the most important sites and monuments. The Chinese government is expecting these archaeologists to do work that normally requires hundreds of years within ten years. There is simply not enough money or manpower to salvage many of these invaluable cultural

valley walls (Kelley & Spilsbury, 1949). Thus, take into account of both human intervention and natural influences, worsening sediment conditions to some extent surge up the debris flow frequency and amplify the magnitude degree.