A culvert is a structure that allows water to flow under a road, railroad, trail, or similar obstruction. They are often used for drainage purposes, constructed using materials like concrete, corrugated steel, or PVC.
A detention pond is a reservoir designed to temporarily hold a set amount of water while slowly draining to another location. Principally used for flood control when large amounts of rain could cause flash flooding.
A retention pond is a reservoir designed to hold a specific amount of water indefinitely. Typically, the pond will drain to another location when the water level exceeds the desired level. This term is often used in contrast to a detention pond.
