Moderation of the Effects of Coastal Processes

Figure 1 - Managing Surface Water and Groundwater

Figure 2 - Bluff Stabilization

Figure 3 - Retaining and Nourishing Beaches

Figure 4 - Tripping Strom Waves

Figure 5 - Paving the Lake Bed

This strategy involves slowing erosion and improving existing shore protection by managing surface water and groundwater (Figure 1) on the land and making coastal slopes more stable (Figure 2), retaining and nourishing beaches (Figure 3), tripping storm waves (Figure 4), paving the lakebed (Figure 5), and other measures. Erosion moderation probably works best in times of low lake levels. When climate change brings more frequent and or more intense snowfall or rainfall, management of surface water and groundwater will become more important and more difficult. More frequent and stronger storms and storm waves will challenge a moderation strategy.

Manage Water on Land

Surface-water management on a coastal property includes the following six steps:

1. Prevent surface water from running over the edge and down the face of a slope. Re-slope the ground away from the edge of the land and build a modest berm near the slope edge. Collect surface water in a storm sewer or in a private drain pipe that can be run down the slope to the lake in a way that does not worsen surface erosion on the slope.
2. Slope mowed lawns, paved roads, driveways, tennis courts, roofs of buildings, and other large drainage surfaces so that water runoff drains to storm sewers or private drain pipes to minimize drainage on coastal slopes and minimize ponding that may add these surface waters to the groundwater flowing toward the coastal slope. A drain system can be installed beneath a lawn to collect infiltrating groundwater and move it away from the coastal slope.
3. Avoid creating tilled gardens and flower beds of significant size near coastal slopes. These gardens and beds may become significant recharge areas for surface water to move into the groundwater flowing towards the slope. The significance of size is a matter of professional judgment for a consultant.
4. Surface-water runoff from seeps or springs on the slope should be diverted from the slope, collected and drained off through private drain pipes mentioned above.
5. Decrease the water velocities of water flowing across coastal land in gullies to reduce the erosive scour potential of this surface-water runoff. Professional help may be needed to minimize ponding and introduction of this water to the groundwater flow beneath the property.
6. Revegetate barren patches on coastal slopes.

Here are some examples of ways to manage groundwater flowing beneath a coastal property and towards the coastal slope:

• In areas of new construction, or construction of new septic systems, leach fields should be located as far from the coastal slope as possible with discharge directed away from the coast.
• Intercept groundwater flowing beneath the property and toward the coastal slope. Trenches and wells must be landward of all possible slope failure surfaces.
• Remove groundwater from perched zones of saturation beneath the land near the slope and slope surface to a depth below the deepest of the potential failure or slip surfaces over which the slope (or portions of the slope) could slide.