A soil and water conservation case study: Little Barton Creek Preserve

Climate Resilience, Nature-Based Solutions

By Joseph “Pete” Van Dyck, owner at Van Dyck Earthworks & Design LLC.

Little Barton Creek Preserve is a privately-owned conservation easement in Dripping Springs, Texas that is dedicated to habitat restoration. This area of Texas is rapidly developing and at risk of both severe drought and flooding conditions. With our help, the family managing this conservation easement has taken creative measures to mitigate these risks and increase wildlife habitat at the same time.

In two years we have transformed a caliche hillside from a barren, lifeless landscape into the most biologically-diverse area of the property. Here’s what we did:

Basins were dug, eight feet wide and nine inches deep, in contour patterns across the landscape for a total of 1,400 linear feet.
The soil excavated from the basins was shaped into garden bed-like berms
The berms were then seeded with a diverse mixture of native grass, wildflower, and cover crop seeds, which were then covered with a protective layer of compost and mulch.
Next, the berms were planted with 40 species of native trees, fruit trees, and pollinator forage trees.

Today, this conservation terrace is well on its way to becoming a richly diverse and abundant food forest for both wildlife and family managing the land.

Photo of the soil conditions before the project began. This was typical of the whole site. This degraded area will be healed when 100% ground cover is achieved. — Soil conditions before the project began. This was typical of the whole site. This degraded area will be healed when 100% ground cover is achieved.

The challenge: Managing runoff and conserving water

For this restoration project, the family chose to tackle one of the most degraded areas on the property. This was a caliche and limestone ledge that had lain barren for as long as anyone can remember. Almost no plants were growing and it was hard to believe that anything could grow in such bleak conditions. The bare surface of the soil had turned into a clay hardpan that would shed most of the rainwater that falls on it, letting very little water filter into the ground. There was also a significant amount of runoff from the road above that was causing a large amount of soil loss when storm water would flow across the bare soil.

What we did

In the above overhead comparison between 2015 and 2017, you can see the new addition of a long, level terrace hugging the contour of the hillside.

This terrace system has the capacity to catch 35,000 gallons of water and will fill up with a hard and fast 1.5-inch rain. The high-calcium caliche soil and fractured limestone bedrock below these structures will filter all of that water completely into the soil within a few hours. This system has filled with water and infiltrated all of that water up to three times in one day. That’s over 100,000 gallons of groundwater recharge in one day on a quarter-acre work site.

The high calcium soils of the Texas Hill Country are known to cause strong runoff, which attributes to flash flooding. However, those same soils allow water to seep into the ground very quickly when this water is pooled, rather than quickly streaming across the surface. During flash floods, storm water must be slowed down and gathered starting near the top of the hill so that energy is dissipated before it enters the main channels. Terraces like the ones used in this restoration project allow us to accomplish this, mitigating damages from both flood and drought.

What this means for water conservation

The bio-swale conservation terraces were built to last for 100 years or more. Over a 25-year period using an average rainfall of 35 inches, we estimate this system has the potential to capture at least 25 million gallons of storm water runoff for an extremely low cost.

This extra water is being put to work serving the local ecosystem. A place with only a handful of species growing before now supports over 100 varieties of trees, grasses, and wildflowers. Excess storm water runoff is allowed to exit the system via spillways built at ground level.

This terrace also protects ancient oak groves downhill, which are now getting access to more soil moisture. The newly-planted trees will one day close the canopy over the barren caliche and connect the forest above and below with a diverse mixture of trees that shades the ground and reduces evaporation from both sun and wind.

The freshly excavated conservation terrace. The berm is soft and tilthy like a garden bed; this makes it easy for plant roots to grow through the soil.

The challenge: Restoring healthy soil

Before it was restored, this hillside was so degraded that it was necessary to bring in compost and some mineral amendments to jumpstart the system.

What we did

A layer of compost was spread an inch thick over the entire area of the berm along with a layer of mulch. This organic layer of materials helps protect the bare soil from the erosive force of heavy raindrops. This addition of organic matter, in combination with the rehydration of the dry soil, has created conditions suitable for our seeds to germinate, and for life to proliferate.

The native seeds and trees that were planted are growing and thriving. Each new green leaf is now photosynthesizing and using solar energy to rehabilitate the lifeless caliche. And for every new one percent of organic soil matter that covers the hillside, the soil is able to hold on to about 25,000 more gallons of water per acre. This information is crucial when trying to achieve habitat restoration.

What this means for soil health

As the hillside’s regenerated soil becomes home to more plants, it creates life cycles in an environment teeming with microorganisms and fungi that help create humus in the soil. This substance holds 80 to 90 percent of its weight in moisture, and therefore increases the soil’s capacity to withstand drought. Humus is located only in living topsoil, and topsoil is only formed when soil is in contact with plant roots. A diversity of plant roots attracts a diversity of soil microbes. By creating the “goldilocks conditions” for life we can change any soil into a healthy living soil, no matter how degraded.

The compost and mulch was spread over the berms to protect bare soil from erosion and reduce evaporation from wind and sun.

The flooded conservation terrace is covered with compost, mulch, and germinating seedlings.

The results: A restored habitat

Since the installation of this project, nearly 100 trees have been planted, including:

Mulberry, escarpment black cherry, rusty blackhaw vibernum, red bud, red oak, Blanco crabapple, sycamore, fig, pomegranate, plum, pear, peach, Monterey oak, Texas ash, Texas persimmon, bigtooth maple, goldenball leadtree, elderberry, roughleaf dogwood, mountain laurel, and many more.

This sycamore tree is surrounded by lush native grasses and grew eight feet in just one year.

There are also native grasses, including:

Eastern gamma, switch grass, Indian grass, Texas cupgrass, buffalo grass, sideoats grama, white tridens, little bluestem, inland sea oats, prairie wildrye, big bluestem, bushy bluestem and others now established on this terrace.

There are many species of wildflowers growing as well. Each tree has been protected with wire cages and the berms have been covered with cedar brush to prevent predation from white tail deer. Each tree is also provided with drip irrigation to help achieve establishment.

This caliche ledge is not just regenerating – it is now a biodiversity hotspot where pollinators, birds, and small mammals will come to feed and spread seeds. This is critical in an area that is becoming extremely fragmented and more developed every day.

Finally, its water-filtering powers don’t just benefit the property’s soil, plants and wildlife. As the hillside guides water runoff underground, it seeps into the area’s groundwater table and helps provide the entire watershed with precious fresh water, all while lessening the often-devastating impacts of flash flooding. This means an unassuming hillside at Little Barton Creek Preserve can have a positive impact on the fish, wildlife and people who live nearby.

To find out more about using storm water to recharge aquifers and restore degraded landscapes please visit http://www.droughtprooftx.com.

Joseph “Pete” Van Dyck is the owner of Van Dyck Earthworks & Design LLC, which specializes in regenerative property design to rehydrate Texas. Pete was a first-place winner at the EPA Region 6 Storm Water Conference GI/LID pro competition in 2017.