The commissioner may, after notice and an opportunity to be heard is given to the permittee, suspend or revoke a permit if he determines that any condition of the permit has been, is being, or is about to be violated or that the permitted activity will impair the operation of any flood control works or impede the maintenance thereof, including access for operation and maintenance; provided, however, that in an emergency the commissioner may suspend or revoke a permit without giving a prior notice or an opportunity to be heard, if such notice and such opportunity to be heard are given within a reasonable time after suspension or revocation of the permit.