It's amazing how you can live close to something for such a long time but never really see it. In my case, it's the Bonnet Carré Spillway. It's basically an overflow valve for the Mississippi River just upriver from New Orleans. When the river level gets dangerously high, the spillway is opened. This allows some of the river water to be diverted, and instead of flowing downstream, it goes into Lake Pontchartrain. The spillway doesn't open all that often, but this year it was opened twice, the first time in its history that that has happened.

It's kind of a big deal when they open up this spillway. Oh, sure, I've seen the water rushing through the trees while I drove over it on the interstate—but that was about it. Well, until recently. I decided to make the trek down there with my younger son. It was fun. Now I can check this spillway off my to-do list.

But wait! This is a great opportunity for some real-world physics homework and estimation problems. Don't worry. I'm going to get you started. I'll give you some basic data on the spillway and then do two estimations for you. After that, you are on your own. Actually, I will start off with this video showing the spillway. It's not perfect, but this is from our trip to see it—also, you can see what this thing looks like.

Rhett Allain

You can even see a jumping Asian carp in this short clip. From that video, you could get a rough estimate of the flow rate—but I'm going to give it to you anyway, along with some other important facts.

The spillway is 7,000 feet long (2,134 meters, for non-Imperials).

There are 350 "bays" that can be opened, and each bay is 20 feet wide (6.1 meters).

The maximum flow capacity is 250,000 cubic feet per second of water flow (you can convert this to m 3 /s as a homework question).

/s as a homework question). The floodway (the land that becomes a temporary river) is 5.7 miles long. At the Mississippi River side, the floodway is 7,700 feet wide. When it gets to Lake Pontchartrain, the floodway is 12,400 feet wide.

Finally, here is a nice table that shows the number of spillway bays open on different days. For the video above (when I visited), there were 138 bays open.

How much power could you get from the spillway?

Suppose this spillway was some type of hydroelectric generator. How much power could you get from it? Let me start with the physics. If you take some water with a mass of m and drop it a height h, it will have a change in gravitational potential energy. This change in energy can be expressed as: