Many rockfill dams are poised to be upgraded in the near future to counteract the expected impacts of climate change on hydrology which can, among other things, result in devastating floods.

Rehabilitation of Svartevatnet dam: placement of riprap stones on the downstream slope. (Photo: NTNU)

Overtopping of an embankment dam has been the cause of about 50% of all embankment dam failures.

Currently, there are over 185 large embankment dams (over 15 meter high) in Norway. These are mostly rockfill dams, with central core of moraine or asphalt. The design of many of these dams has to be reviewed in the near future in line with the Norwegian Dam Safety Regulations. The review may lead to upgrading of the dams, e.g. considering potential extreme loading conditions of overtopping due to new flood conditions arising from the effect of climate change on hydrologi.

Hence, it is of importance to design efficient overtopping protection systems.

Multitudes of past research investigations conducted to study rockfill dam failure under overtopping flows have stated that the probability of initiation of failure at the dam toe is high.

Need for stability

The research project with the working title ‘Embankment dam safety under extreme loading conditions’ was initiated by HydroCen to address the issue of dam toe instability under overtopping conditions.

The primary objective of the project is to come up with a technically effective and economically efficient means of providing adequate stability for rockfill dam toes under overtopping flow conditions.

In order to accomplish the set objectives of the project, physical modeling investigations at the Hydraulics laboratory in NTNU, Trondheim are underway. Also, the possibility of large scale field tests is also being considered.    

Experimental setup at the hydraulics laboratory, NTNU, Trondheim