Long-term behaviour of dams that have experienced internal erosion (sinkholes)

Rockfill dams Earthfill dams
Timing of internal erosion incident: Generally during first filling or within first year. There are also rockfill dams where incidents occurred years into operation. Generally a few years into operation or after several years.
Possible early-warning sign: Increase in leakage, Muddy leakage, Pore-pressure variations
Possible warning-time between first sign and internal erosion incident: Account for the majority of dams with no warning, or up to days–weeks “warning-time”. However, there are also rockfill dams where there have been months or longer “warning-time”. Generally months or longer between first sign and the incident.
Location of internal erosion incident: Higher incidence where dams: i) abut to concrete structures and/or sheet pile walls, and ii) are placed on irregular foundation.