The idiomatic way to say this is "Woodland Pond is formed by an earth dam." This works in all registers from regulatory documents to casual conversation.
Carlton Pond Waterfowl Production Area is a 1,055-acre (4.27 km2) artificial pond and wetland located in the town of Troy in Waldo County, Maine. The pond is formed by an earthen dam which backs up Carlton Brook.
wikipedia: Carlton Pond Waterfowl Production Area
Ice is cut from these ponds by Earl Carpenter & Sons They also receive ice from Northbridge and Dodgeville At North bridge the pond is formed by the railroad embankment cutting off a bend in the Blackstone river There is an open connection under the track between the pond and the river and the river water at times flows into the pond.
Annual Report of the Superintendent of Health..., Issues 1-14
(vi) Summary of Site Preparation and Construction Activities: The Ash Pond was originally constructed
between 1960 and 1965. The pond is formed by a continuous dike referenced as the east, south, north,
and west dikes. The crest elevations of the dikes are as follows: the east dike ranges from 102.6‐ft to
113.6‐ft, the south dike ranges from 95.5‐ft to 103‐ft, the west dike ranges from 95.5‐ft to 103.2‐ft, and
the north dike ranges from 103.3‐ft to 113.6‐ft.
Source: Alabama Power Company