The emergency spillway cannot be shut down. Runoff from upcoming storms will cause the lake to rise again, and likely spill over the ES again.
The parking lot area is not a designated spillway. Erosion to that area is a big concern for future spillovers. The water inlet in front of the parking lot is another problem
About a day before the emergency spillway started overflowing, one of their engineers in a briefing said that the parking lot was designed to be part of the system. He recalled that, at one time, people were planning to build some bleachers somewhere on the parking lot; and the safety engineers vetoed it because it would have interfered with the parking lot's drainage function.