Slope Stabilization & Erosion Control in Philadelphia, PA

Slope stabilization and erosion control in Philadelphia is about keeping soil where it belongs long enough for roots to take over. North and west of the city, the Piedmont breaks into creek valleys with steep wooded sides, and the suburbs are full of homes built into hillsides, regraded back yards and new swales cut to move stormwater. When those slopes are left bare, rain carries the soil off, gullies form, and the sediment ends up in an inlet or a creek. Our erosion control services cover everything from a single eroding bank behind a house to long runs of ditch and basin slope on a development site.

Why slopes here fail

Upland soils like the Chester series are silt loams over silty clay loam subsoil, weathered from mica schist. The USDA lists slopes on them from 0 to 65 percent. Silt loam sheds water as a thin sheet and then cuts rills once flow concentrates, and the subsoil exposed by grading takes seed poorly. Philadelphia averages about 44 inches of precipitation a year, with heavy summer thunderstorms, so a bare slope rarely gets a gentle first rain. Shade from mature oaks and tulip poplars on wooded lots slows grass, which leaves soil exposed even longer.

Hydromulch for moderate slopes

On moderate grades, a heavier hydromulching coat is often enough. Penn State Extension describes hydromulching as spraying wood fiber or paper mulch with water and a tackifier over seed and soil, and lists rates of 30 to 40 pounds per 1,000 square feet on level and gentle ground and up to 3,000 pounds per acre on steep slopes. We raise the rate and tackifier with the pitch so the mat holds through a hard storm while still letting seedlings through.

Bonded fiber matrix

Bonded fiber matrix, or BFM, is a hydraulically applied mulch with a stronger bonding agent; once cured, it forms one unbroken layer that still lets water through. It is used where a slope is too steep or too long for standard hydromulch but where blankets would be hard to anchor or install, such as rocky cuts and irregular banks. It costs more than standard fiber mulch, so we use it where the slope calls for it.

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Erosion control blankets

For the steepest pitches, channel bottoms and anywhere water concentrates, we use erosion control blankets: rolled mats made of straw alone, a straw and coconut fiber mix, or pure coir, laid over seeded soil and stapled down. Straw blankets break down fastest and suit lawn-edge slopes; straw-coconut and coir blankets last longer for steeper banks and swales. Penn State notes mats and covers must be anchored with pins or staples, and placing them in full contact with the soil, trenched in at the top, is what keeps water from running underneath.

Swales, ditches and basin slopes

Drainage swales are often the first thing to wash out on a new lot because they are built to carry water. We seed and blanket the channel, then hydromulch the side slopes. Stormwater basins get the same treatment on their banks. Where the plan calls for permanent turf reinforcement or riprap, we coordinate with the site contractor.

Creek-side and wooded properties

The Wissahickon, Pennypack, Neshaminy, Perkiomen and Brandywine valleys all have homes on steep ground above the water. On those lots we favor shade-tolerant fine fescue mixes, keep mulch rates high and avoid disturbing tree roots any more than needed. Where a homeowner wants something other than turf, native grass and wildflower seeding can go on a stabilized bank; University of Delaware Extension advises meadow seedings go in no later than October 31 in fall or May 31 in spring.

Matching the method to the slope

A quick rule we use on the site visit: gentle yard slopes take a standard lawn hydroseed, moderate banks take heavy hydromulch with extra tackifier, steep or long slopes take BFM or blankets, and channels take blankets. The written estimate shows which treatment goes where.