PROPAGATION OF FLOOD WAVE CAUSED BY TAILINGS DAMS COLLAPSE

Abstract

Embankment dams’ collapse is often caused by overtopping during flood wave – caused by insufficient spillway capacity. Collapse can also be caused by progressive seepage through the dam’s body as a result of increased contact seepage alongside an internal manmade waterway. Other causes for dam collapse, include: slope instability of embankment dams, damages in the dam body caused by earthquakes, liquefaction of earth dams under static and seismic action, and flood waves caused by earthquake – induced landslides into the reservoirs from the valley sides [1]. According to ICOLD, the most common reason for embankment dams’ collapse is overtopping – 30÷35% of all registered cases. During dam collapse, as result of the immediate discharge of the impounded water in the reservoir – or impounded flotation tailings at tailings waste lagoon - in the downstream river valley, a catastrophic flood wave makes its hazardous way towards destruction. Normally, the time needed for the flood wave warning system to activate, is much shorter than the time needed for the formation of the flood wave caused by rainfall – runoff. Thereafter, depending on the location of the dam, a potential dam collapse – especially in case of tailings dam collapse – could result in catastrophic losses of human lives, destruction of agricultural land and long-term degradation of the environment. In this manner, as follows, results of 2D analysis for flood propagation at a cascade system of tailings dams Sasa 3-2 and Sasa 4 are analyzed. Both cascade dams are located in the northeast part of RN Macedonia, on river Saska. The analysis is conducted with the use of the software program HEC RAS.