If the breach isn't plugged yes the water will and did equalize. This levee was on a canal coming from the lake. I am convinced that a heavy army engineer battalion could have plugged the canal and repaired the levee.
Levees may look impressive, but FWIU they are actually quite fragile. Once a levee starts washing over, it becomes weaker VERY quickly. I don't know exactly at what point people stopped working on the levees, but there comes a point where the amount of effort required to delay flooding by 'n' minutes becomes essentially exponential with 'n'.