Bit of a strange question..

[Betrivent]

I asked a friend a random question the other day. He didn't know the answer but pointed me here, to this forum. So here you go, random geographical question that I'm very curious about.

So I found a drawn picture of Vancouver from 1898, where what is now the rail yards east of science world was a fairly large expanse of what I assume was water/mud. And 1st ave used to be a waterfront street. And of course on the present day map, we have the skytrain and a rail line running through a shallow canyon that leads right to where this body of water would have been.

My question is, is that corridor natural, as in, the result of a stream? Or is it man made?