Editing Contour line (section)

=== Environmental science ===
In discussing pollution, density maps can be very useful in indicating sources and areas of greatest contamination. Contour maps are especially useful for diffuse forms or scales of pollution. Acid precipitation is indicated on maps with '''isoplats'''.  Some of the most widespread applications of [[environmental science]] contour maps involve mapping of [[environmental noise]] (where lines of equal sound pressure level are denoted '''isobels'''<ref>{{cite web |url=https://www.sfu.ca/sonic-studio/handbook/Isobel.html
|access-date=2010-04-25
|title=Isobel
|website=www.sfu.ca
|date=2005-01-05
}}</ref>), [[air pollution]], [[soil contamination]], [[thermal pollution]] and [[groundwater]] contamination.  By [[contour planting]] and [[contour ploughing]], the rate of [[water runoff]] and thus [[soil erosion]] can be substantially reduced; this is especially important in [[riparian]] zones.