Internal erosion is especially dangerous because there may be no external evidence, or only subtle evidence, that it is taking place. Usually a sand boil can be found, but the boil might be hidden under water. A dam may breach within a few hours after evidence of internal erosion becomes obvious.
Internal erosion manifests by the migration of soil particles by suffusion or piping.
Suffusion is the migration of soil particles through the soil matrix.
- [http://qjegh.lyellcollection.org/cgi/content/abstract/13/1/53 Development of piping erosion conditions in the Benson area, Arizona, U.S.A.
- The scaling law of piping erosion (PDF-Datei; 898 kB)