Middle Level Bill: Revival

I thank my hon. Friend—he is a very good friend—for giving way. I am listening to him with rapt attention, and I heard him say that the entirety of the Middle Level is below sea level. I do not know the area, so could he tell me if that means that the rivers cannot get out—does the stuff have to be pumped out?—and traffic on the waterways cannot get out of this sunken level? I admit that I am pretty ignorant about the area.