Boats are also a source of NPS pollution, including sewage and trash that is purposefully released to the water, and gasoline and oil that accidentally leaks from engines. In addition, erosion of soil can lead to increased sediment levels in waterways, another type of NPS pollution. Finally, runoff can carry animal wastes from holding pens or grazing fields into waterways. In addition, timber cutting equipment must be driven across rivers and streams. These operations can increase erosion and release nutrient-rich sediments, contributing to the NPS pollution process.
Channelization increases water flow rates and changes water flow pathways.
This may cause NPS pollution by both increasing erosion rates and increasing the quantity of pollutants reaching downstream sites. Dams may cause other NPS pollution problems because sediment and other pollutants build up behind the dam. When the water is released, large levels of these NPS pollutants may be carried downstream. Finally, development near erosion-sensitive stream banks and shorelines accelerates erosion processes beyond natural levels. These activities contribute excessive sediments and other pollutants to the waterways.