Hill Country Flooding 2025
The latest flooding disaster in the Texas Hill Country on July 4th is giving me flashbacks. To have it happen again to children who deserved to safely enjoy nature, is soul crushing. Especially knowing that we as a community could do so much better.
A decade ago, the 2015 Memorial Day and Halloween Floods devastated Wimberley and San Marcos. The lessons learned from those events inspired the creation of ERA.
We have a tendency to clean up excessively in these situations and it damages nature's ability to heal itself.
Watch this video from the Hill Country Alliance for expert advice, amazing recovery footage and check out the list below for some tips and lessons learned from the 2015 floods along the Blanco.
Key actions for river recovery in the short term:
Leave as much woody debris as possible (unless it impedes search and recovery efforts or the removal of true trash). Sorting through piles will likely be necessary in many cases, but rather than piling this wood to burn, create brush berms!
Avoid cutting trees that look dead unless they're hazardous. Many will recover by next spring! You'll be amazed. Don't rip up any trees that still have roots in the ground, even if they're completely sideways, they still have a chance of re-growing or becoming an incredible anchor for future river recovery.
Allow native bunchgrasses to regrow. Mow as little as possible, preferably just a path and space to hang out. The deep roots of these species help to prevent erosion and their tall leaves sway to help slow flood waters.
Avoid compacting the soil along the river. Drive as little as possible with vehicles and heavy equipment. While some equipment work is 100% necessary for getting large objects out of the flood zone, it is best if operators can "follow their tracks" and disturb as little of the soil as possible as they do what needs to be done.
Slow water down uphill as much as possible. This is more of a long term project, but worth thinking about at this stage, because there's a temptation to smooth and grade while equipment is around. Having speed bumps for water is actually much better than creating a compacted area that water rushed off of.
Don't turn land into a waterslide! This makes future flooding and erosion worse (re-read the item above and really let this sink in)
Avoid burning along the river banks. Use that wood as a resource for helping the river recover by shaping woody debris into "brush berms" whenever possible.
Remember to be kind and spread love. Care for each other and care for the earth is critical.
Don't forget the good memories and that there is hope.
The river and communities along it will recover and still be beautiful. It's just going to take some time and TLC.
Now, let’s switch to thinking long term and planning a more desirable future for the next generations:
There are ways that we can make our rivers safer and more resilient.
Yes, we need better early warning systems, but what I'm referring to goes deeper. Infrastructure is key to improving conditions for life. In this case "green stormwater infrastructure" techniques can make the difference that's needed to shift us from a future filled with repeated devastating floods (and droughts) to a desirable future where our springs, rivers and creeks keep flowing, not flooding, for future generations.
Thoughts and prayers don't build infrastructure. We can start there. But then we need to follow up with actions: analysis, designing, building and maintaining systems that protect and improve quality of life by slowing, spreading and sinking water into the soil.
What does that infrastructure look like? Well that depends on the scale.
For a residential home: A rain garden (think temporary pond) dug into the ground can catch rainwater off the roof, yard and driveway, then sink that rain into the ground faster than mosquitoes can breed. All that water benefits the plants in the yard, helps recharge the aquifer and reduces the amount of water flowing downstream. There’s an example of a rain garden at the Upper Guadalupe River Authority Headquarters, where I’ve presented about the rain gardens numerous times.
For medium acreage: Conservation Terraces (aka berms and swales) are a great way to sculpt the earth to retain water for longer. These function similarly to rain gardens, but they're usually more linear. This is an oldie but a goodie. Back in the Dust Bowl Era, we eventually stopped saying "oh whoa is us, there's nothing we can do" and started to implement practices to conserve soil and water, like these. You can still see some of the old Civilian Conservation Corp terraces around the hill country today, if you know what to look for. Unfortunately, many of these terraces have been bulldozed by folks who don't know better. Check out WaterRanching to learn more about these.
For large acreage ranches: Sometimes a space is too big for human labor to cost effectively do the work of shaping the landscape, even with heavy equipment. In these instances, we can turn to animal impact to help us. Bison and beavers were critical to the original ecosystems of Texas. The wallowing action of bison built rain gardens, and they fertilized the prairie grasses, helping to create rich soil that retained water (more on that momentarily). Beavers made dams that helped the water stay in upland areas longer. While we can't put back beavers or bison in most circumstances, we can use "biomimicry" to imitate how they affected the landscape. Cattle can be managed to imitate bison herds. Usually they're managed in a way that is destructive to land health, but Holistic Planned Grazing allows ranchers to use livestock to increase soil carbon on vast scales, which helps with water retention (I'll explain this mechanism momentarily). There are examples in the Kerrville area of exactly this, such as at the Kerr Wildlife Management Area.
People come out to Kerrville and the Hill Country in general to camp and experience nature because it appears to be pristine. Sadly, that’s far from the truth. We’ve dramatically altered these landscapes with our land management practices.
Isn't flooding just a natural process in this area? Yes, this is true. But this area also was naturally covered in very different vegetation: woodlands and prairies are wonderful sponges.
Trees (yes, even cedars) on slopes help slow water down and infiltrate it into the soil. Clear cutting too much on the slopes and overgrazing the prairie to nothing have damaged the natural mechanisms that historically made the hill country more resilient to flooding.
Less than 1% of the prairie remains in Texas. The prairie plants had roots reaching 10+ feet down, creating root channels to direct rainwater deep into the soil profile. The native prairie grasses have fish-net like roots that stabilize soil against erosion. These roots also act as a carbon pump, because of the annual cycles of dormancy these grasses go through. They pull down carbon from the atmosphere as they grow, then in winter some of those roots decompose, locking up that carbon underground. The grasses you see in our pastures now are mostly shallow-rooted invasive species that don't serve the same ecological functions. The 6 inches of root depth in turf grass don’t help with water retention or carbon sequestration the way that prairie grasses do.
Some people have noted that this area of the Hill Country doesn’t really have soil. It has rocks. This is true of our damaged landscape. Historically, there was much more top soil in this region held in place by prairie grasses, which meant more water storage capacity in the soil of the hills. As the water moved through the soil profile, some also trickled into the aquifer to emerge later as spring flow that keeps our rivers crystal clear and sparkling even in drought conditions.
What does soil have to do with flood prevention? Prepare to have your mind blown!
Start thinking of soil as a tool for holding water. It’s essentially a sponge. The soil can hold massive amounts of water. How much water the soil can hold varies based on how much carbon (or organic matter) there is in the soil. The carbon pump action of native bunch grasses helps make the soil richer. Some prairie remnants have up to 12 percent soil organic matter!
How do we decrease the intensity of floods and increase our resilience to them? It isn’t impossible, even in an era of climate change. Soil organic matter is critical to solving this. Some key facts that give me hope:
For every 1% increase in soil organic matter, the soil gains anywhere from 16k-27k gals of water storage capacity per acre! (Natural Resources Conservations Service and Natural Resource Defence Council).
One inch of rain falling on 1 acre of ground is equal to about 27,154 gallons. (U.S. Geological Survey)
Put these 2 numbers together and you can understand that:
For every 1% increase in soil organic matter, the soil can hold another inch of rainfall!
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Let’s do a lofty thought experiment based on these numbers:
Imagine if we implemented practices to effectively store more water in our soil! If we can increase the soil organic matter by 10 percentage points, then even this drastic rainfall event would have produced very little runoff and therefore very little flash flooding. What if anything under a 10 inch rain didn’t produce ANY flooding? What if the 12 inches of rain in the future only made the river flood as much as a 2 inch rain now?
Remember, storing water in the soil or in the upland in earthworks doesn’t “steal” it from the river. It still eventually gets there. Just as a clean clear flow out of a spring. Not as a muddy, rushing torrent.
So, with this in mind, how do we increase our soil organic matter by that much? Has anyone even done this? Yes, it has been done. The key is implementing practices that improve soil health. Adding compost, manure, mulch, cover crops, native bunch grasses, compost tea, mycorrhizal fungi, and beneficial microbes are all part of the equation. Basically it boils down to increasing the biological activity in the soil. I’ll let y’all proceed down this rabbit hole on your own.
(There are some details here such as rates of rainfall, different soil types gaining different amounts of storage, but for the sake of simplicity, I’m trying not to get too deep into the weeds while still accurately getting this point across).
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In our own practice we had a client in Medina where we started from caliche (just white chalk for soil), added a bunch of composted manure and plants, then tested the soil 3 months later and were at 6% soil organic matter. I still kick myself for not testing before we started to establish a baseline. An estimate is that the caliche and lawn was 1% or less soil organic matter before we started (this is sadly typical for lawns and overworked land). With that, reaching 6% is a 5% increase, or 100k gals per acre of water storage capacity gained.
We’ve seen these systems with increased soil organic matter far exceed the design capacities that we and engineers have expected. This warrants further research, which our landscaping company isn’t equipped for, but we’re staying tuned as organizations like the Edwards Aquifer Authority work with the scientific community to quantify the benefits of nature-based solutions to flooding.
If there’s a silver lining to the horrific tragedy of the Hill Country flooding on July 4th, I hope that it inspires us to be more resilient. Let there never be a next time, because we learn how to be better stewards of our whole watersheds from the hilltops to the rivers.
Asking how much time people had after the warnings is the wrong question. I’m seeing too much emphasis put on the warning systems. That’s the final step in disaster preparedness. Of course it’s important and needs significant improvement. Sirens save lives by giving people a chance to get out. We should have them. But shouldn’t we want more than that?
If we want to mitigate the devastation of flooding, we’d be served better by asking:
How do we more effectively slow, spread and sink rainwater into our landscape?
