Evolution of Coastal Zones

Lost Lake Area of Louisiana, USA. Landsat 5 image from 1985 on left, Landsat 8 from 2015 on right. Data courtesy of NASA/USGS.

Lost Lake Area of Louisiana, USA. Landsat 5 image from 1985 on left, Landsat 8 from 2015 on right. Data courtesy of NASA/USGS.

Coastal zones are the place where the sea and the land meet, and they’ve played a massive role in the life of Pixalytics. From a personal standpoint we’re based, and live, in Plymouth on the south-west coast and anyone who saw the Dawlish railway tracks swinging in midair eighteen months ago will know how these areas can affect our transport links. In addition, Sam’s PhD was focussed on the ‘Remote Sensing of Suspend Sediment in the Humber Estuary’, and so Pixalytics has effectively been grown from a coastal zone!

Last week the BBC carried a report highlighting the erosion of the Louisiana coastal wetlands; in particular, it noted that more than an area the size of a football pitch was disappearing every hour. This statistic caught our attention, and our next steps were obvious! We downloaded two images of the Lafourche Bayou in Louisiana; the first was a Landsat 5 image acquired on the 31st August 1985, and the second was a Landsat 8 image acquired twenty years later on the 02nd August 2015.

Mouth of Atchafalya River, Louisiana, USA. Landsat 5 image on left from 1985, Landsat 8 image from 2015 on right. Data courtesy of NASA/USGS.

Mouth of Atchafalya River, Louisiana, USA. Landsat 5 image on left from 1985, Landsat 8 image from 2015 on right. Data courtesy of NASA/USGS.

The image at the top of the blog shows the area around the Lost Lake, in the bottom left hand corner, just off the coast of Louisiana; with the 1985 image on the left, and the 2015 image on the right. The loss of land, described in the BBC report, can be seen in the northern portion of the image with a lot more water visible. However, the image on the right shows the mouth of the Atchafalya River in Louisiana; again, the 1985 image is on the left. Coastal evolution is again clearly visible, but this time there are islands that have risen from the water.

Swamplands, like in Louisiana, aren’t the only coastal zones changing. In 2011, the United Nations Environmental Programme estimated that over the last 40 years Jamaica’s Negril beaches have experienced average beach erosion of between 0.5 m and 1 m per year. Another coastal zone in decline are mangroves and wetland forests; a 2007 report noted that the areal extent of mangrove forests had declined by between 35 % and 86 % over the last quarter half century (Duke et al. 2007).

Coastal zones have social, economic and environmental importance as they attract both human settlements and economic activity; however, they are also particularly susceptible to the impacts of climate change and their evolution will have impacts on the human, flora and fauna populations of those areas. So when you’re next at the coast have a good look around; the view in front of you may never be seen again!

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