Stormwater management and compost use

sedimentationStormwater management is the act of controlling the course of water that originates during precipitation events in a way that prevents or lessens damage caused by flooding, erosion/sedimentation and water pollution.

Adding compost restores soil organic matter and, thereby, restores natural soil functions.  Compost use in stormwater management is critical to an efficient, economical program for controlling the impact of rainwater in areas disturbed by human activities.

Healthy soil vs. damaged soil

In a natural soil system, the topsoil layer is continually replenished by the decay of plant and animal matter.   The result is a thick, porous layer of soil that holds water.   Significant volumes of water are retained after rain events, moving laterally through the soil to hydrate plants before percolating to groundwater.  Vegetation covers and anchors the soil, minimizing erosion potential from excess flow to rivers and streams.  This is a healthy soil.

But in areas where the topsoil has been removed or depleted without replenishment,  the soil that remains may be little more than dead, inert subsoil incapable of supporting life.

When the topsoil layer no longer exists:

  • Vegetation may be sparse or nonexistent.
  • There are no microbes to facilitate nutrient uptake or degrade contaminants.
  • Runoff flows in higher volumes to surface waters without impediment, carrying soil particles and pollutants.
  • The volume of water available to percolate to the aquifer is greatly reduced.
  • Synthetic nutrients must be applied in greater and greater quantities to compensate for runoff losses.

The environmental and economic consequences of a damaged soil system not only impact locally, but also far down stream.  But compost adds essential components for water retention and pollution mitigation by delivering soil organic matter (SOM) and active microbial populations.

Stormwater plans that ignore the role played by the soil in water management fail to address the root cause of stormwater runoff.  Soils with the recommended organic matter level of 5 percent can eliminate runoff from a typical rainfall event in many parts of the country and reduce overall runoff volumes by as much as 50 percent.   Fixing the soil is, by far, one of the least expensive ways to manage water, costing less per gallon stored than any other stormwater management strategy except using native plants.

Learn more about stormwater management and sediment/erosion control

Soil health: key points