Water Flows Downhill

Rivers are usually in the lowest part of a landscape. Picture the bottom of a valley: water flows downhill and collects in streams that flow into increasingly larger waterways that make their way back to the ocean. That’s why in most places the land right next to the streams and rivers is prone to flooding. Hence the term floodplain.

So why is New Orleans / Bulbancha different?

Here, the highest ground is right by the river. This is because the city is located on a distributary delta. This landscape was created over time by the Mississippi River overflowing or breaking through its banks and depositing sediment (sand, silt, and clay) wherever floodwaters flowed. Because the largest and heaviest soil particles were deposited closest to the river, the land by the river is the highest (the levees) and slopes down and away into lower lying, swampy areas.  

Since the highest ground is closest to the river and water flows downhill, the rain that we get flows away from the river towards Lake Pontchartrain and the coastal wetlands. At the lakefront, however, human-constructed levees protecting the region from high tides and hurricane storm surge impede the flow of water and require the use of large drainage pumps to remove water from the city. (Much more on this in future posts)

Water flowing via tributaries into a river & Water flowing from river into distributaries