is it legal to dam a creek on your property

[DeRemington]

No, it is generally not legal to dam a creek on your property without obtaining the proper permits, even if you own both sides of the stream. Waterways are often considered public resources, and regulations exist to protect their flow, wildlife, and the stability of the stream itself. The specific regulations and permitting process will vary based on your location, the size of the creek, and the scale of the proposed dam, so you must check with local, state, and federal authorities.