Which type of water flow is managed by the vegetated emergency spillway?

The vegetated emergency spillway is specifically designed to handle flows that exceed the principal spillway's design capacity. Its primary function is to provide a safe outlet for excess stormwater runoff or floodwater that could potentially overwhelm the primary system, thus preventing damage to the infrastructure, including the dam or detention basin.

When inflow from rainfall or snowmelt surpasses what the principal spillway can manage, the emergency spillway allows this additional water to flow over or through a designated path. This helps ensure that the water level remains controlled, reducing the risk of erosion, structural failure, or uncontrolled flooding downstream. The vegetation typically present in these spillways also aids in stabilizing the soil, thereby mitigating erosion during these high-flow events.

The other types of water flow mentioned do not relate directly to the function of the emergency spillway. For instance, flows below the principal spillway's design capacity do not require the additional capacity that the emergency spillway provides. Similarly, consistent low-flow conditions and intrusive groundwater flows are managed through different mechanisms and do not fall under the emergency spillway's responsibilities.