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Recognizing Runoff through the Watershed

Non-Point Source (NPS) Pollution is defined by the Environmental Protection Agency as any pollution that does not travel to rivers and streams through a pipe. All pollution that comes out of pipes is regulated by permits as point-source pollution. NPS pollution is what is carried by rainfall runoff. It is not regulated by permits.

In the Barataria and Terrebonne Watersheds NPS Pollution includes things like disease-causing organisms, turbidity, and organic-matter enrichment. The damage caused by these pollutants can limit the way we use waterbodies in these watersheds.

Frequently it is possible to predict the type of pollution that will affect a waterbody by examining the way the land draining into it is used.

The image below is a 1993 Thematic Mapper image of the Barataria and Terrebonne Watersheds with 30m resolution. Click on the name of one of the basins to view that basin and then higher resolution aerial photograph images of the smaller watersheds (we call it a subsegment) that make up each larger watershed. This will allow you to learn more about land uses in the subsegment and whether the waterbodies in the subsegment are polluted.

Click for more information about viewing the Aerial Photographs of each subsegment.


  1. - Watershed Image
  2. rainfall runoff - file not found -

  3. Aerial Photographs - file not found -

Rainfall Runoff Defined

Runoff is... Water movement across the surface of the land. This only happens during a particularly big rainfall or when it has been raining for an extended period of time and the ground is already saturated. Each individual drop of rain falls wherever it may, and becomes runoff, flowing into storm drains, ditches, bayous, and other low areas, seeking the lowest parts of the watershed, and ultimately sea level and the ocean. Rainfall runoff picks up various pollutants, like small pieces of trash, sediment, nutrients from yards or farms, and carries them with the water as non-point source pollution.

Intro 2

An aerial photograph can tell you a lot about the land it pictures. Look at the photo below. Do you see a lot of water? Is it a stream or pond, a bay or the Gulf? Is it intermixed with land, so you can barely tell where water ends and land begins? Often this means there are wetlands in the photograph. Wetlands are very common throughout the Barataria and Terrebonne Basins.

Features you may see on these photos show human activity as well as natural features. Human-made features to look for include: roads, canals, agricultural fields, urban or industrial areas. Natural features you may see include: wooded forest or swamp, marsh, ponds, streams, lakes and bays. Think about how the activity on the land might cause pollution that could be carried into nearby waters when rain falls and creates Runoff.

To learn more about the source of this aerial photo (DOQQ) and how to find specific features, go to the Imagery Page. Or go back to the Website Introduction associated with the Satellite Image of the Watersheds.


Runoff - zbtnep_water/client_files/ftp_files/Pollutant_Pages/Runoff_Defined.htm

Imagery - zbtnep_water/client_files/ftp_files/Imagery/Imagery.htm

Barataria Terrebonne Watersheds
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