As some one who watched the Trade Center go up and worked in and around those buildings for almost twenty years, I don't have to look at the footprint. Between the Trade Center and the Hudson River are a couple of hundred yards of earth upon which is built the World Financial Center. As for your comment that Lower Manhattan would have been washed away, your ignorance of the geology of the area is astounding.
I am glad you know with such assurance what is possible. In the course of your work did you work out the math of the total force of two such huge buildings falling simulateously? Guess you did that on your lunch period. More to the point, when they were designing those basins and figuring out how strong to make those foundations, did they ever anticipate what did happen on that day? I doubt that the question was ever raised, just as they never expected the building to be hit by airplanes not yet designed.