Dry and soaked soil contributing to flood risk in Mid-MO

After a wet summer across most of the area, flooding is starting to sound like old news. But a closer look at the ground tells a more complicated story, and it splits between our northern and southern counties.

Most of the area has stayed wetter than normal since early summer, even though July brought a dry stretch. That combination has created two slightly different ground conditions depending on where you live.

In the south, soils are still saturated from months of consistent rainfall. Up north, drier conditions through July have had the opposite effect, hardening and compacting the ground. Both situations raise the risk of flash flooding through different mechanisms.

Soil acts like a sponge, with pore spaces between particles that absorb and hold water. When soil is already saturated, those pore spaces are full. There’s simply nowhere for new rainfall to go.

Instead of soaking in, that water sits on the surface or runs off immediately, funneling into streams, ditches, and low-lying areas faster than the ground can process it. That’s the picture in our southern counties right now, where the soil’s water storage capacity is essentially maxed out.

It seems counterintuitive, but dry ground can create the same runoff problem. When soil dries out for an extended period, the particles compact and settle tightly together, reducing those pore spaces. In severe cases, dry soil can develop a crusted, almost water-repellent surface layer.

That compacted structure means water can’t infiltrate quickly, even during a heavy downpour. Instead of soaking in, rain sheets off the hardened surface a lot like rain hitting pavement. Our northern counties could be seeing a hint of this due to drier-than-normal conditions from last month.

Much of Mid-MO's soils can’t handle a sudden burst of rain, either due to too much water or too little. The risk of flooding right now isn’t just about how much rain falls, but also about what kind of ground it’s falling on.