Final answer:
Lahars can occur independently of volcanic eruptions, triggered by factors such as rainfall and melting snow. The Mount St. Helens eruption example shows how lahars can cause significant destruction. Thus, the possibility of a future lahar with a substantial discharge exists, with or without an eruption.
Step-by-step explanation:
Lahars can indeed happen at any time, including long after the most recent volcanic eruption. A lahar is a type of mudflow or debris flow composed of pyroclastic material, rocky debris, and water that flows down from a volcano, typically along river valleys. Lahars can be triggered by intense rainfall, the rapid melting of snow and ice, or the release of water from lakes or reservoirs, even when there is no eruptive activity. The catastrophic eruption of Mount St. Helens on May 18, 1980, is a notable example where lahars were a significant secondary hazard that followed the volcanic event.
The instability of volcanic edifices, compounded by the presence of loose volcanic material and often extensive snow and ice cover, means that lahars can occur without a triggering eruption. These flows can be extremely dangerous and destructive, as witnessed during the Mount St. Helens eruption that transformed the landscape and led to fatalities and significant damage to infrastructure.
Given the inherent instability of volcanic regions and factors that can trigger lahars independently of eruptive activity, a flood with a discharge similar to a previous event could potentially occur in the future, regardless of whether there is a concurrent eruption.