Sources of Pollution: Sediment Resuspension


Description:

Resuspension occurs when sediment that has settled to the bottom of a bayou, lake, or bay is redistributed through the water. Waves created by wind or boat wakes most frequently cause this, but sometimes it can be caused mechanically by dredging.

 

How does this land use cause Non-Point Source Pollution?

Whether sediment and organic matter are from natural or man made sources, they can still cause pollution. Eventually, both can settle to the bottom of the waterbody. Any activity that changes the way the water flows over the water bottom, such as wind, boats, storms, or high winds, can resuspend the sediment and organic matter.

  • Organic Matter/Low D.O: Anytime organic matter enters a waterbody it can cause the dissolved oxygen to drop. Resuspension of the organic matter from the bottom can act like fresh organic matter has entered the water, causing the dissolved oxygen to drop.

  • For example, after Hurricane Andrew and more recently Hurricane Lili, there were large fish kills because resuspension of large amounts of sediment during the high winds brought massive amounts of organic material into suspension, and used up all the oxygen in the water, so the fish suffocated.

  • Sediment: Sediment and organic matter in the water decrease the amount of light that can travel through water. When sediment is resuspended from the bottom of the water, it can take several minutes to several days for that sediment to fall back to the bottom and the water to clear up. This limits the distance light can travel through water, which limits photosynthesis. It also limits the visibility for animals that have to find food.

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