Runoff negatively affects water quality
When an area is developed or altered, the way water flows is also changed. As land surfaces are covered with impervious surfaces (roads, driveways, roofs, etc.) less water can seep into the soil, so runoff increases. This increased runoff is usually channeled into ditches, drainageways, storm sewers or road gutters and often ends up in nearby lakes and streams.
High flows of water can cause flooding or erosion, as well as increasing sediment in streams and lakes. Fine sediment can also transport nutrients such as nitrate or phosphorus, and pollutants such as sands or salts from icy roads. All of these processes have an adverse effect on water quality.
Planning ahead is the first step (and most important) in preventing or minimizing erosion due to runoff. An easy way to do this is to pretend that you are a raindrop. In looking at the landscape or any impervious surfaces, which route would you travel? Obviously, you would want to take the easiest path downhill. Keeping that in mind, note any areas that runoff would choose to travel.
Evaluate your property before you begin your landscape design. Consider slope, soil type and existing vegetation as you plan your development.
Problems caused by runoff and possible causes
- Water near shore is cloudy: from excess sediment reaching water.
- Oily rainbow film on the water: from possible petroleum contamination.
- Algae blooms, green scum or abundant plant growth in the water: from excess nutrients such as nitrate or phosphorus reaching the water.
- Washouts, trenches, small piles of sediment, leaves or debris at the bottom of slopes: from excessive runoff across the property.
Long-term best management practices
Follow these practices to minimize runoff and prevent erosion:
- Limit paved and covered areas that prevent water from seeping into the ground.
- Invest in permanent stabilization practices for long-term protection of your shoreland property. These include planting new vegetation, installing erosion control structures and diverting drainage.
- Retain trees and shrubs. Trees provide a natural umbrella by shedding water and can reduce runoff by as much as 50%.
- Plan and complete an annual maintenance schedule to make sure that your runoff and erosion control plan is working to protect your property.
- Limit clearing and grading on slopes. Minimize cutting and filling for roads, sidewalks and footpaths to reduce erosion and still provide access.
- Avoid damaging adjacent property with temporary erosion control methods. Water does not stop flowing at your property line.
- Use existing natural drainage systems such as valleys or low areas instead of digging new ditches.
- Design culverts and drainage structures to handle excessive amounts of runoff. Assistance is available from your county Soil and Water Conservation District (SWCD) or the Natural Resources Conservation Service (NRCS).
- Protect storm sewers from sedimentation so they are able to carry storm water as intended.
- Minimize pavements and impervious surfaces.
- Stay away from slopes. Locate driveways, sidewalks, stairways and footpaths away from slopes. Steeper slopes have greater erosion potential. If you must cross a hillside, follow the contour of the slope.
- Sweep driveways or sidewalks instead of washing them down with a hose. This helps prevent sediment, salt and petroleum products from washing into storm sewers.
- Cover stockpiles of salt and sand with a tarp or store them in a building.
- Don't pave wasted space (such as corners near buildings) that are not large enough for parking or driving.
- Use gravel driveways instead of pavement.
- Where paved areas are necessary, locate them as close to the main road as possible to minimize the length of paved driveway.
- Minimize road crossings over waterways. Cross at a right angle to the stream if possible.
- Use shallow grassed areas by roadsides instead of curb and gutter runoff and storage for snow.
- Install water bars on sloping roadways to slow and divert runoff.
- Use paving stones for walkways instead of solid concrete. This allows water to seep around the stones instead of running off.
- Use steps on a slope. When a walkway must go directly up and down a slope use steps, particularly near the waterfront.
- Avoid shortcutting down slopes. Shortcutting causes erosion. Compacted soil on footpaths also promotes excessive runoff.
When landscaping, stage construction so one area is stabilized before another area is disturbed.
Avoid construction in areas with:
- Little vegetative cover (preserve the existing cover).
- Erodible soils (sands or soils that appear fluffy when dry).
- Mainly bedrock with a thin covering of soil.
- Steep slopes of greater than 10%.
During construction, control erosion by using temporary methods such as:
- Diversions to carry water away from the construction site to where it can be safely dispersed.
- Silt fences or hay bales to trap sediments before they enter the water.
- A combination of methods may be the best solution.
Construction near shoreland
The following are best practices for construction near shoreland:
- Use only clean fill (free from debris and dirt) such as rock, sand or gravel near lakes and streams.
- Use only solid concrete forms such as interlocking blocks or slabs. Don't use liquid concrete and avoid treated timbers or railroad ties.
- Drain utility trenches of water, then backfill, seed and mulch.
Inspecting erosion control
Inspect erosion control on construction projects frequently:
- Immediately after initial installation of erosion control measures.
- During construction.
- Following any severe rainstorm.
- Before reseeding.
- When nearing the completion of construction work.
- At the end, when temporary erosion controls should be removed. Ensure that stabilization is complete and drainageways are in proper working order.
- Install rain gutters along the edge of rooftops to help carry water off of the roof and away from the building to areas where soil won't be eroded. Make sure there is erosion protection where the gutters outlet onto soil.
- Keep gutters free from debris and draining properly.
- Keep rooftops free of snow and ice buildup. This helps control the magnitude of runoff in the spring and protect your roof from damage.
- Pave patios with flagstones or decay-resistant wood blocks instead of solid material to permit some water to seep around the stones or blocks.
- Position rooftops so they are perpendicular to the slope, instead of parallel, to slow down runoff.
Most zoning ordinances restrict the amount of impermeable surface allowed in the shoreland area. Check with your local zoning officials for more information.
- Alteration or filling of wetlands is strictly regulated. Check with your county Soil and Water Conservation District before beginning any projects that impacts wetlands.
- For any development along waterways or lakeshores, contact the Minnesota Department of Natural Resources, Division of Waters for any necessary permits.
Remember: It's Minnesota law to call 811 before you dig.
Reviewed in 2018