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EarthDesignLand design with David Sussberg

Water and landform · 7 min read

What Are Earthworks and Contour Swales?

From EarthDesign, the land-design practice of David Sussberg

The short answer

Earthworks are deliberate changes to the shape of the ground, such as ponds, swales, berms, terraces and check dams, usually made to slow, spread, store or redirect water. A contour swale is a level ditch with a mound on its downhill side, built along a contour line so water collects and soaks in rather than running off.

Swipe the diagram sideways to read all labels.

Cross section of a contour swaleGround slopes from uphill on the left to downhill on the right. Runoff flows downhill into a level basin dug along the contour, with a mounded berm on its downhill side planted with a tree. Dashed arrows show water soaking into the soil below the basin.Runoff flows downhillWater soaks inBasinBerm (downhill side)UphillDownhillCross section. The basin runs level along a contour line.Only suitable where soil, slope and climate allow.
Cross section of a contour swale. Swales only suit some soils, slopes and climates; on-site verification and professional review come first. Conceptual illustration, not to scale and not a prescription for any site.

Contour swale vs. drainage swale

The word swale is used for two opposite things. A contour swale is dug exactly level so water stops and infiltrates. A drainage swale, common in road and stormwater design, is graded slightly downhill so water moves away. Building the wrong one, or a contour swale that is not truly level, can concentrate water and cause the erosion it was meant to prevent.

Other common earthworks

  • Ponds: store water in a natural low point, with a planned spillway for overflow
  • Check dams: small barriers in a gully that slow flow and catch sediment
  • Spillways: controlled overflow paths so excess water leaves without cutting a new channel
  • Keyline patterns: cultivation or ripping lines laid out from a key point to move water from valleys toward ridges
  • Terraces: level benches cut into steep slopes

When earthworks are a bad idea

Earthworks are not universally appropriate. Situations that call for caution or professional review include:

  • Steep slopes or unstable soils, where saturated berms can slump or slide
  • Clay soils that barely infiltrate, so water sits rather than soaks
  • Shallow bedrock, septic fields, foundations or buried utilities nearby
  • Wetlands, streams or shared drainage that may be regulated
  • Climates where rain mostly falls when soil is frozen

How a map helps the decision

A topographic map shows where contour lines run, where water collects and how large each catchment is. That is enough to sketch candidate locations and rule some out. Before any digging, a qualified person should verify levels on site, call before you dig, and confirm permit requirements.

Limitations

  • This article is educational and is not engineering design. Ponds and dams may be regulated by state or local agencies.
  • Field verification, utilities location, permits and safe construction remain the responsibility of the landowner and their licensed contractors.

Apply it to your land

Earthworks and Keyline Planning

Some land benefits from shaping water with earth: on-contour swales, a pond in the right draw, check dams in a gully, or a keyline pattern across a field. Some land does not. This plan starts by finding out which applies to yours.

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EarthDesign is a digital design and visualization platform. Outputs are advisory; site execution, regulatory permits, and licensed professional sign-offs remain the responsibility of the client and their licensed contractors. No warranty of fitness for a particular purpose is made, expressed, or implied.

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