I am in Indiana, but the state laws that we abide by were mandated nationally by the EPA or Army Corps. You will likely need a dam permit from the DCR and possibly a construction in a floodway permit (in Indiana the cutoff for needing one is a drainage area smaller than 1 square mile). In Indiana floodway permits require mitigation of all trees removed on a 5:1 (depending on location) basis and a 5 year reporting period. A 404 permit will be required from the Army Corps. if wetlands or areas within the streambed are disturbed. And finally and erosion and sediment control permit (Rule 5 permit in Indiana) will likely be needed if it is not for agricultural use and disturbs and acre or more. I have never applied for these permits in Virginia, but in Indiana this is a job for an engineer. More permits might be needed, but these permits would be required in Indiana and are mandated by federal law (clean water act, navigable waterways act, and floodway act)and should apply in one form or another in Virginia.
