"[A]lthough New Orleans' situation is geographically magnificent, located at the mouth of the great Mississippi with its vast network of tributaries, the actual site is miserable, swampy land located in a dangerous, hostile environment, where the Mississippi debouches into the Gulf. The site's problems are numerous. The older and main parts of New Orleans rest on the natural levees of the Mississippi, about fifteen feet above sea level, with the firmest, most solid soil being silt. Most of the modern city is at or below sea level, with the Mississippi usually flowing past the city at a height of ten to fifteen feet above sea level, flooding at twenty feet. Behind the old city, between river and lack, until recently, was a backswamp, with no solid building foundations, which was a breeding ground for malaria until 1900. During heavy rains, the area filled up with water."