Controlling Wateratthe HarvestSite

ByTomGilbert WaterResources Specialist

MaineForestService

As we move into the spring field season, the Maine Forest Service is developing a new series of “Level 1” BMP trainings which put extra emphasis on controlling water and minimizing disturbance at the harvest site. These are 2 of the 7 “fundamental BMPs” we have focused on in past trainings and are also mentioned in our BMP manual. Some of the main concepts in controlling water at the harvest site include:

▪ Understanding how water moves within the harvest area, and decide on control measures;

▪ Installing a system throughout the site to slow down runoff and spread it out;

▪ Reducing water velocity and volume (“The 2 Vs”); and

▪ Protecting the natural movement of water through wetlands if they must be crossed.

Site topography is an important consideration, since water will gain momentum as it travels down steeper slopes. The more velocity water gains, the more soil will erode. Keep in mind there are always water inputs upslope.

Also keep in mind that it is easier and more effective to control water in small amounts. This can be done by installing effective BMPs in the right locations throughout the site. By managing water in small volumes throughout the site, and diverting it to undisturbed forested areas, you are greatly reducing erosion potential.

The diagram demonstrates how runoff is diverted into undisturbed forested areas in small volumes throughout the site. Several types of structures are used to divert runoff in many locations, preventing runoff from gaining volume or velocity so the forest floor is able to absorb the water. Note that in all examples, water is diverted outside of the buffer, represented by lines located along the stream channel. Buffer areas are in place as a last line of defense. It’s the system of BMPs used throughout the site that keep our water clean. Minimizing or avoiding impacts to wetlands is another way to reduce the volume and velocity of water at your harvest site. Wetlands contain a large amount of water in the soil, so driving through them with machinery will compact the soil and displace water, which may then travel to other locations of your harvest site. If a wetland cannot be avoided, minimizing impacts with corduroy and culverts as needed will reduce water displacement by increasing bearing capacity and allowing for the natural movement of water.

I hope to catch up with everyone during our Level 1 BMP training sessions this spring to discuss these and other topics in more detail. Until then stay safe!

For more information on fundamental forestry BMPs please see our field friendly BMP manual, Protecting Maine’s Water Quality, available on our website: https://www.maine.gov/dacf/mfs/ policy_management/water_resources/ bmps.html