We set up the erosion pins and sediment traps on a steep lot in the Patterson Park area last spring before any grading started. The equipment includes a rainfall simulator calibrated to Baltimore’s 10-year, 24-hour storm event, plus an automated runoff collection system tied to dataloggers. This field setup captures real data on sheet erosion rates and rill formation on the site’s weathered mica schist and colluvial soils. We then analyze those samples in the lab using the Revised Universal Soil Loss Equation (RUSLE2) to estimate annual soil loss under proposed grading conditions. That combination of field instrumentation and computational modeling gives developers a defensible baseline for their sediment control plans.
Combining field runoff plots on Baltimore’s Piedmont saprolite with RUSLE2 modeling provides erosion rates that hold up under ASCE 7 review.
Method and coverage
Regional considerations
Compare a site in the Canton waterfront district with a cut slope in the Guilford neighborhood: the Canton fill over soft estuarine silt yields a sediment yield four times higher than the Guilford residual saprolite, even with the same slope angle. Without a site-specific erosion analysis, the developer in Canton might size a sediment basin based on generic tables — and end up with a basin that overflows after a single 2-year storm. Baltimore’s heavy clay content in the topsoil also makes rill erosion worse than sheet erosion, so standard universal soil loss equation numbers alone under-predict the actual sediment load reaching storm drains.
Standards that apply
ASCE 7-22 (Ch. 6: Flood Loads & Erosion Considerations), IBC 2021 (Ch. 18: Soils & Foundations – Erosion Control Referenced), ASTM D4647 (Pinhole Dispersion Test for Dispersive Clays), FHWA-NHI-05-017 (Hydraulic Engineering Circular No. 17)
Related services
Erosion Hazard Screening (Phase I)
Desktop review of NRCS soil surveys, topographic maps, and historical aerial photos of the Baltimore site. We produce a preliminary soil loss estimate using RUSLE2 with default K-factors, identifying high-risk zones that need field verification.
Field Erosion Assessment (Phase II)
Installation of erosion pins, sediment traps, and runoff plots on representative slopes. We measure actual soil loss over at least one wet season or a simulated storm event, calibrating the RUSLE2 parameters to Baltimore’s local rainfall erosivity (R-factor ~175).
Erosion Control Design Support (Phase III)
Using the Phase II data, we model proposed grading, stabilization measures, and sediment basin sizing. Deliverables include isopach maps of predicted erosion thickness, recommendations for matting type (jute vs. coir), and a sediment delivery ratio report for MDE review.
Typical parameters
Common questions
What is the difference between sheet erosion and rill erosion in Baltimore soils?
Sheet erosion removes a uniform thin layer of topsoil from the entire slope, while rill erosion concentrates flow into small channels that cut deeper. In Baltimore's Piedmont saprolite, rill erosion typically accounts for 60–70% of total soil loss once the slope exceeds 8% grade, because the silty loam crust seals quickly and generates concentrated runoff.
How much does a soil erosion analysis cost in Baltimore?
A typical Phase I screening runs between US$930 and US$2,540 depending on lot size and complexity. Phase II with field monitoring adds more, usually US$2,500–US$5,500 per monitoring period. We recommend contacting our team with your specific acreage and slope ranges for a tailored quote.
Do I need an erosion analysis for a small residential lot in Baltimore City?
If your lot disturbs more than 5,000 square feet or is located on a slope steeper than 15%, the Baltimore City Department of Public Works typically requires an erosion and sediment control plan supported by a soil loss estimate. We can run a quick Phase I analysis for those single-lot projects that satisfies the plan reviewer without the expense of full Phase II monitoring.
How does Baltimore's rainfall erosivity (R-factor) compare to other Mid-Atlantic cities?
Baltimore's R-factor hovers around 175–180 in the RUSLE2 database, which is higher than Philadelphia (R ~150) but lower than Richmond (R ~210). That means a standard erosion blanket rated for a 10-year storm in Philadelphia may not provide adequate protection for a Baltimore slope of the same geometry, because the rainfall energy is about 17% greater here.
What is the pinhole dispersion test and why is it relevant for Baltimore sites?
The pinhole test (ASTM D4647) identifies dispersive clays that collapse and erode rapidly under flowing water, even at low velocities. Dispersive soils are common in Baltimore's Piedmont zone, particularly in the Wissahickon Formation schist. If undetected, a dispersive subgrade can lead to piping failures under a paved driveway or within a compacted fill slope within two or three heavy rain events.