Keuka Lake Book
Drainage and Runoff
How water moves over and through the ground is important to those of us who have experienced flooded basements, wet yards, or broken septic systems. Solving the problems associated with surface water runoff and poorly drained soil is also important to improving the health of Keuka Lake.
Rain from roofs, driveways, and fields runs off, often eroding yards, destroying plants and washing away soil. Much of the soil is carried into streams and eventually reaches the lake, visible in the sediment plumes spreading from the stream mouths after any significant rain. The added sediment decreases water clarity allowing less sunlight to penetrate the water. Fish and their eggs can be smothered and destroyed by sediment plumes.
Many of the streams entering the lake receive substantial amounts of sediment due to human influence on the land. Vegetation buffers, rip rap, or infiltration devices installed by homeowners and farmers help to decrease the amount of sediment in streams and ultimately Keuka Lake. Nutrients, such as nitrogen and phosphorus are needed in small amounts in the lake to support the foodchain. Excessive amounts carried in runoff can cause algae blooms and deplete oxygen needed by the lake's animals. Runoff may also contain pesticides, oil, antifreeze, and other substances toxic to life in the lake.
Pollution also occurs when the soil is too wet to filter septic outflow. Effluent can percolate into the groundwater without proper filtration, or it can rise to the surface and be carried into streams and the lake.
There are inexpensive ways you can control excess runoff created by roofs, patios, driveways, sidewalks, and swimming pools. Whatever the soil drainage condition in your neighborhood, swales (a depression in the ground that moves drainage water but doesn't prevent traffic from easily crossing), berms (a slight "bump" in the ground surface that controls water), and basins can control runoff on your property by reducing its speed and increase the time over which the water is released. For example, land immediately adjacent to your house should slope away from your home, removing water that could collect around and seep through the foundation. Once the water has been carried ten feet from the house, using a gentler grade slows the water and allows infiltration into the soil.
On properties where drainage is poor, you can regrade the land to create a basin which holds all runoff and allows it to infiltrate into the soil over a longer period of time. The effectiveness of a basin depends on the soils ability to absorb and filter the surface water. Soils with less than two feet of depth to bedrock or one foot of depth to a seasonally high water table, soils having a high clay content or a clay hardpan beneath the surface, or low-lying soils that receive runoff from a large land area may not have sufficient infiltration capacity. In these situations, the soil will rapidly become saturated, and water that is intended to filter down through the soil will collect on the surface and can create health, safety, and use problems or move across the surface as excess runoff.
Persistent wet patches in your yard could indicate that the soil around your house has settled, preventing proper infiltration. Filling these pockets with topsoil and seeding them with grass will usually solve the problem by eliminating the depression. Another possible solution is a subsurface drainage systems such as tile. These systems are essentially porous underground pipes that collect water as is seeps into the ground and shunts it down grade to the end of the pipe. By providing a place for the water to go, the water is prevented from pooling. In situations where the water causing problems originates elsewhere, a system of berms and/or swales might be considered. These systems redirect the surface flow away from areas of concern or restrict the flow to a specific area of your property.
When manipulating flows, it is always important to make sure that while solving one problem you are not creating another. Because runoff control can be such a complex issue, it is recommended that you contact the local Soil and Water Conservation District Office for solutions to water problems or before undertaking any major projects that will have an impact on existing runoff conditions.
Installing Infiltration Devices
The installation of various infiltration devices can enhance infiltration even on sites with well-drained soils. It is important to remember that surface runoff cannot infiltrate certain soils. Under these conditions, surface runoff cannot infiltrate the soil even with an infiltration device.
By using berms and swales, you can speed site infiltration by channeling surface runoff into a gravel filled seepage pit, a French drain, or a gravel-lined detention basin. You can also spread runoff over the land surface by using a series of terraces or runoff spreaders, which promotes greater infiltration by slowly spreading runoff in a fan-shaped pattern across a vegetated land surface. Seepage pits, gravel-lined recharge basins, and terraces lose their effectiveness as infiltration devices when the land surface is clogged with clay, silt, or fine sand particles. Infiltration devices for large parcels of land are often constructed along with sediment traps, basins, or grassed sediment filters. These traps and filters remove fine particles from runoff before they reach the infiltration device. Sediment traps are usually needed for most residential lots. Most homeowners can use a system of swales or basins leading to the infiltration device as a sediment filter.
Permeable Paving Surfaces
As homeowners, we can't live without driveways, sidewalks, or patios. Water landing on paved surfaces and rooftops carries much of the pollutants on these surfaces and can degrade nearby streams. The stream may be out of sight, but underground storm drains often carry rainwater runoff from the impervious surfaces surrounding your home directly into a nearby stream. By using paving surfaces that allow rainwater to soak into the ground, you can reduce excessive rainwater runoff and help prevent erosion.
A paved surface that allows water to soak in may seem impossible, but there are many materials that provide the durability of concrete while allowing rainwater to filter down into the ground. If you are planning a new patio, walkway, or driveway, and your home site has favorable soil conditions, there are several attractive alternatives to concrete.
Wood decks, usually installed for their functional good looks, can serve as a form of porous pavement. Redwood and treated southern pine (the two most commonly used deck materials in this region) are as durable as most other paving surfaces. Decking allows rainwater to soak into the ground beneath it, and the space between the planks provides ample room for precipitation to drain directly onto the soil surface. As long as minimal air space is maintained between the soil surface and the decking, wood rot can be minimized.
If you are installing a new patio or rebuilding a crumbling sidewalk, you don't need to use the typical slab concrete. Using bricks, interlocking pavers, or flat stones (flagstone, bluestone, or granite), you can construct an attractive, durable walkway. If placed on well drained soil or on a sand or gravel bed, these modular pavers allow rainwater infiltration. Although chemicals are sometimes used to control weeds growing in the joints between the pavers, Corsican mint or moss can crowd out weeds and add beauty to the paved area.
Pre-cast concrete lattice pavers also rest on a bed of sand and gravel and allow rain to soak slowly into the ground. These paving materials can be used wherever natural soil drainage is good and there are no problems with either bedrock near the surface or seasonal high water. Lattice pavers won't work on clay or other soils that are already saturated with water.
Significant strides have been made in developing porous asphalt pavement in the last three decades. This material is similar to conventional asphalt in durability, but it contains a much smaller percentage of very fine particles. As a result, the asphalt allows water to soak through to the base material and into the soil below. Almost twice as much porous asphalt must be applied to achieve the same strength as conventional asphalt. The finished surface must be protected from excess silt and fine sand so that its pores don't become clogged. You can use porous asphalt on your new driveway or encourage its use on streets and parking lots in your community.
Diverting Rain From Paved Surfaces
For many years, pavement construction standards called for any rain reaching a paved surface to be controlled and directed by a system of pavement and pipe drains. Roof downspouts spill onto driveways that are graded down to street gutters, which, in turn, lead to storm drains that dump the accumulated rainwater directly into streams. The destructive torrents of this collected rain have helped erode countless miles of streambanks.
In places with good soil drainage, you can capture, spread, and infiltrate rainwater from paved areas and roofs to minimize the erosive force of the flowing water. Though many sidewalks and driveways are appropriately graded to spread runoff onto lawn areas where it can soak in, steep slopes, poor grading, or concentrated flow from downspouts can sometimes cause destructive and unsightly erosion. In these cases, stabilizing the eroding area where runoff leaves the pavement can dissipate the water's erosive force and allow infiltration. Dense vegetation, mulch (possibly held in place by netting), or gravel can serve this purpose.
If the volume of runoff can't be effectively controlled, the runoff can be captured as it leaves the paved surface. The water can be channeled and spread to either a low-lying grassy area or a series of terraces, both of which allow gradual absorption into the soil. In more severe cases, gravel-filled seepage pits along the pavement's edge or French drains can be used to take in large volumes of runoff and encourage infiltration.