Flood!

I was going to end my ecology lecture today by looking at climate projections for the Midwest, which looks like will be shifting to more intense rainstorms in shorter periods of time, exacerbating flood risks.

A bit ironic that we had to cancel due to a historic flood, eh?

The Yellow River is now at 16.2 ft, which is major flood stage. It is expected to crest at 18.0 ft by tomorrow morning, exceeding the previous flood record of 17.1 ft in 1954.

Flooding, of course, is a natural phenomenon. It is a regular ecological force of disturbance that is necessary for certain species to exist. It can change the entire course of a stream or river in a single event. It uproots trees, creating log jams (which lots of critters call “habitat”). It exposes soil, giving space for seeds to germinate. It deposits new sediment and nutrients on the floodplain. It connects sub-populations of species (a friend of mine has researched some frogs who relying on “rafting” on debris during flood events to exchange genetic material across isolated wet spots).

Of course, floods are also damaging for humans. We rely on water bodies for many reasons, and we place our houses, roads, crops and infrastructure nearby. We build and pave straight roads across the landscape to get here and there. Floods are disruptive. When they don’t happen for awhile, its easy to get lulled into complacency (see: Houston, New Orleans, Miami, the Mississippi River, etc).

Flooding is not just a function of precipitation. It is exacerbated by impervious surfaces like parking lots and buildings, which accelerate water towards the river instead of allowing it to slowly seep into the ground. Agricultural watersheds, especially those with artificial drainage, also increase flooding relative to natural cover like grasslands or forests.

In our circumstance, we first had a lot of snow, which melted very fast, followed by 6-8 inches of rain over the last few days. We normally average about 2.3 inches for the entire month of February.

The image below shows rainfall over the last 7 days across northern Indiana (via NOAA).

The rainfall and land use to the Northwest of Plymouth – in the headwaters – determines what how high the Yellow River rises in downtown Plymouth.

Map via Marshall County Soil and Water Conservation District

When the rain started, the land was already water logged from melting snow. The land use is primarily agricultural, so artificial drainage accelerates the water away from the fields and towards the main course of the river.

Here are a few photos I took of the Yellow River in Plymouth today: