On a Houston site, the first thing we deploy is a skid-steer mounted hydraulic probe to collect undisturbed samples from the top 6 feet. The city sits on Beaumont Formation clays and sands, which are notoriously prone to rill and gully erosion after heavy rain. Our crew uses a direct-push rig to extract Shelby tubes and bulk bags, then runs them through a full soil erosion analysis that includes dispersion tests, pin-hole tests, and shear strength at varying moisture levels. This data feeds directly into the ensayo CBR to evaluate subgrade loss under traffic, and into our slope stability models. Every report is calibrated to Houston's 50-inch annual rainfall and its flat drainage patterns.
One inch of topsoil loss in Houston's clay can reduce slope safety factor by 40% in a single storm season.
Methodology and scope
Houston's geology is dominated by overconsolidated clays of the Beaumont Formation, interbedded with sand lenses that create preferential flow paths. During a soil erosion analysis, we measure dispersivity using the Crumb test (ASTM D6572) and the pinhole test (ASTM D4647) to identify sodium-sensitive clays that collapse upon wetting. The parameters we record include:
Critical shear stress (τc) from a jet erosion test (JET)
Erosion rate index (k_d) for cohesive soils
Liquid limit and plasticity index to estimate shrink-swell potential
In-situ moisture content and dry density from nuclear gauge
These values help us predict erosion volumes for stormwater channels and detention ponds. For steep lots near the Buffalo Bayou, we cross-check results with a georradar GPR survey to map buried sand layers that can accelerate subsurface piping.
Technical reference image — Houston
Local considerations
Houston has 2.3 million residents and over 35 federally designated flood zones. The city's flat topography means that even a 2-year storm event can trigger sheet erosion across cleared lots. Without a proper soil erosion analysis, developers risk silt runoff into protected waterways, which triggers EPA fines under the Clean Water Act. Worse, concentrated flow along utility trenches can undermine foundations. We've seen cases where a missing erosion analysis led to a 6-foot-wide gully forming overnight behind a retaining wall. Our reports quantify the erosion potential and recommend sediment basins, check dams, or erosion-control blankets specifically for Houston's clay soils.
Field mapping of gullies, rills, and sheet erosion across the site. We produce a 2D erosion potential map using the Revised Universal Soil Loss Equation (RUSLE2) calibrated with local rainfall erosivity (R-factor ~350). The report includes sediment basin sizing and temporary diversion recommendations.
02
Slope Erosion Stability Analysis
For cut slopes and embankments, we run limit-equilibrium models (Bishop simplified, Morgenstern-Price) that incorporate erosion-induced strength loss. We measure root reinforcement from existing vegetation and model the effect of a 100-year storm on factor of safety. Results guide the need for riprap or turf reinforcement mats.
03
Erosion Control Plan (SWP3) Development
We author the Stormwater Pollution Prevention Plan (SWP3) required by the Texas Commission on Environmental Quality for projects over one acre. The plan is based on our field data: soil textural class, infiltration rate, and runoff curve number. We include inspection checklists and stabilization timing for Houston's 9-month wet season.
Applicable standards
ASTM D4647 (pinhole test), ASTM D6572 (Crumb test), ASTM D5852 (erodibility of soil in place), IBC 2018 Chapter 18 (stormwater & erosion control), EPA NPDES Construction General Permit (CGP)
Frequently asked questions
How much does a soil erosion analysis cost in Houston?
A standard erosion analysis for a 5-acre residential development in Houston ranges from US$800 to US$2,340, depending on the number of test pits, lab dispersion tests, and the complexity of the drainage model. Larger commercial sites with multiple outfalls may exceed that range.
What is the difference between sheet erosion and gully erosion?
Sheet erosion removes a uniform layer of topsoil across a slope, often invisible until the subsoil appears. Gully erosion cuts deep channels that can reach 3 feet or more. In Houston's clay, sheet erosion is common on bare lots after a thunderstorm, while gully erosion typically follows concentrated flow along construction access roads.
Do I need an erosion analysis for a lot that is already graded?
Yes, especially in Houston. Grading removes the natural vegetation and topsoil structure, leaving the Beaumont clay exposed. Even a lot that looks flat can have micro-topography that channels runoff. Our analysis identifies weak points before they become compliance issues with the city's drainage regulations.
How long does it take to get the erosion analysis report?
We typically complete field sampling in one day for a standard lot, lab work takes 3 to 5 business days, and the final report is delivered within 7 to 10 days. If you need accelerated turnaround for a permit submission, we can prioritize the report in 4 business days at a premium.
Location and service area
We serve projects across Houston and its metropolitan area.
