In this study, we wanted to compare the suspended sediment load of the Hudson and Columbia Rivers based on the 1988 and 2009 Landsat datasets. We chose the two rivers based on geographic location in the United States, one on the east coast and one on the west coast, but both in the north. Landsat data sets were obtained from the United States Geological Society (USGS) by using GLOVIS for the seasonal range of late spring to early summer. This time period was used as the rivers would be expected to be higher due to melting of the winter snow/ice and vegetation starting to grow. Idrisi was then used to create composites from the datasets to determine suspended sediment in the outflow of the rivers.
The Hudson River is located in eastern New York. The river begins at Henderson Lake, located in northeast New York. The major tributary to the Hudson River is the Mohawk River. Located just south of where these two rivers join is the Federal Dam. Once it gets past the dam, the Hudson River flows between the Catskill and Taconic Mountains and then passes between Manhattan Island and the New Jersey Palisades where is empties into the Lower New York Bay in the Atlantic Ocean, completing a course of over 500 km (Townsend and Donick, 2003). From the 1940s to the 1970s polychlorinated biphenyls (PCBs) were discharged into the river. It is estimated that the total amount of PCBs discharged was about 1.3 million pounds. The high levels of PCBs in the river placed it on the EPA’s National Priorities List and beginning in 2002 a 60 km section of the Hudson River was dredged (EPA, 2012). Landsat imagery that was gained for processing from 1988 is from July 30, and the 2009 is from August 25.
Image of Hudson River drainage basin (HRWA, 2012). The river is in blue, where the drainage basin area is in green. The blue star indicates the approximate area of study.
Natural color composite of the Hudson River using bands 1, 2, and 3. Dark green shows vegetation; blue and black are water; brown gray and white represent bare land and anthropogenic influences. The 2009 image has some clouds that appear are white in color. In the 1988 image, suspended sediments are indicated by the milky blue color and in a light brown color. Note in the 2009 image, there’s no visible suspended sediment.
False color composite using bands 1, 4, and 3. Green represents vegetation; blue is water; pinks and purples are bare land or anthropogenic influences. The light pink color shows suspended sediments. Note that again in the 2009 image there is no visible suspended sediment.
False color composite made using bands 1, 3, and 7. Reddish brown colors are vegetation; blue is water; light blues, grays, and pinks are bare land and anthropogenic areas. Suspended sediments are yellow-green and milky blue. As in other images, there is no visible suspended sediment in the 2009 image.
Special composite made by overlaying band 3 over 1 and then using bands 2, 4, and 3/1. Black represents water; green shows vegetation; pinks and purples show land and anthropomorphic areas. Suspended sediments are a purple-pink to milky pink color. Suspended sediments are not visible on the 2009 image.
Looking at these images, it can be determined that there was more suspended sediment in 1988 than in 2009. This may be due to the amounts of PCB discharged in the river and the fact that dredging of the river began in 2002 and is ongoing.
The Columbia River is the "fourth largest river by volume in North America" (NPCC, 2012) and is approximately 2000 km long. The drainage basin is approximately 670,000 square kilometers and covers the states of "Oregon, Washington, Idaho, Montana, Nevada, Wyoming, and Utah, as well as British Columbia in Canada" (Lang, 2012). Currently there has been a push by the US Army Corps of Engineers for rehabilitation on the jetty system at the mouth of the Columbia River. The most recent "repairs occurred in 2007 based on the increased storm activity" (USACE, 2012). The Landsat datasets are from June 19, 1988 and May 28, 2009.
Image of Columbia River drainage basin (Wikimedia, 2008). The river is highlighted in purple. The yellow/green shows the extent of the drainage basin. The green arrow is pointing to the approximate study area.
False color composite using bands RGB=132 (visible color bands). In the 1988 image are blue is water, brown/red is land, milky blue is suspended sediment, and green is active vegetation with a little plume going into the Pacific Ocean. The 2009 image shows a larger plume into the ocean, where the blue is water, land is red/purple, active vegetation is a darker purple and can see the texture of the trees, and the suspended sediment is a milky blue/purple.
False color composite using bands RGB=137. The 1988 image shows the water as blue, land as red/brown, and suspended sediments as a milky blue/green. 2009 image the water is blue, the land is purple and the suspended sediment is a milky blue.
False color composite using bands RGB=125. In the 1988 composite water shows as blue, land is red/pink, and suspended sediments as milky blue. The 2009 image water is bright blue, land is red/pink and suspended sediment is milky blue.
False color overlay image using bands RGB=24 3/1. An overlay image of bands 3/1 was made and used in the green band for the composite. The black is water, land is green and pink, and suspended sediments are purple. The 2009 image water black/blue, land is green and pink, sediment is milky blue and purple.
In all the images there seems to be more suspended sediment in the 2009 images. This may be because the 2009 Landsat data are from May, closer to springtime mountain ice/snow melt, where the 1988 data is from June. Also the jetty work from the increased storm activity would release some of the caught sand and sediment into the water.
For the Hudson River, there is more suspended sediment in 1988 than 2009, possibly because of constant dredging. The Columbia River seems to be opposite from the Hudson, by having more suspended sediment in 2009 than 1988. Comparing the two localities, the Columbia River had more suspended sediment in both years, possibly because the Columbia has a longer track and has an increased amount of storm activity. For future study of these areas, seasonal variation of the suspended sediment could be looked at, to determine if yearly conditions are a factor in the output.
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