Logging BMPs Protect Land And Water

By Terence Hanley | August 2, 2002
From Missouri Conservationist: Aug 2002

Every year, Missourians cut, split, peel and saw great quantities of wood from the state's private and public forests. Logs, bolts, blocks and sticks are among the most obvious and tangible of our forest products. It's easy to estimate the dollar value of these products. It comes to millions in raw materials alone.

Manufacturing secondary wood products such as barrels, handles, ties, posts, and pallets contributes millions of dollars more to the state's economy.

A forest is more than trees, though, and forestry is more than just harvesting timber. Along with trees and other plants, forests help produce clean water for drinking, swimming, recreation and other uses. That's why it's important to keep soil in place rather than let it erode into rivers and lakes. We can't afford to give up wood products - nor would we ever want to - but we can reduce erosion and provide for clean water while still harvesting timber. The way to do this is by understanding and applying Missouri's best management practices.

Best management practices, or BMPs, are voluntary measures designed to reduce erosion and runoff from timber harvest operations. They have been developed by individual states in response to the Federal Water Pollution Control Act of 1972 and the Clean Water Acts of 1977 and 1987. In Missouri, BMPs have been in effect since 1987, when a number of agencies, including the Missouri Department of Conservation (MDC) and the Department of Natural Resources, developed "Missouri Watershed Protection Practices." Collectively, this is a series of guidelines for maintaining watersheds and protecting streams. These guidelines, published in booklet form by MDC, offer loggers and landowners specifications for putting BMPs to work. The guidelines also appear in the booklet, "Forest Management for Missouri Landowners." Both booklets are available from local MDC offices or the main office in Jefferson City.

Understanding why BMPs are needed and how they work begins with an understanding of soil erosion and its effects. Erosion is a natural process whereby natural, physical forces move particles of rock and soil from one place to another, sometimes far from their place of origin. This process has slowly shaped our landscape over millions of years. The effects of natural erosion can be seen from the rounded hills of the Ozark highlands to sandy and gravelly Mississippi River bottoms. Human activity, however, often accelerates erosion by exposing soil to the effects of wind, water and gravity.

Farming, construction and road building regularly expose soil to natural forces that break apart and dislodge soil particles. This exposure is where erosion begins. Compaction of soil by heavy equipment compounds the problem by causing increased runoff. Rather than being absorbed, rainwater runs along the surface of compacted soil, building force and volume along the way. This runoff carries soil particles downslope or downstream. Levels of water-borne soil can increase to the point that water quality becomes degraded. When this happens, soil - as sediment - becomes a pollutant.

Very little erosion occurs in a healthy and vigorous forest. The crowns of trees, the foliage and stems of shrubs and herbaceous plants, ground-level woody debris and leaf litter absorb much of the force of falling raindrops. Mineral soil is largely shielded from impact by organic material above it. In addition, forest soils are porous and easily absorb rainwater once it hits the ground. Consequently, there is little runoff, so little sediment leaves a forest environment.

That changes when a logging operation moves into the woods, but not as you might expect. Logging itself results in little erosion. Vegetative cover and leaf litter are still largely intact once a tree is felled. Most of the sediment flowing from a timber harvest area comes from soil exposed on skid trails, haul roads and log landings. BMPs help soften the impact by reducing erosion and runoff during and after a logging operation, and by shortening the time it takes for the forest to return to a pre-harvest condition.

Best Management Practices fall into two broad categories. They are: 1) measures to reduce erosion and runoff (and to eliminate chemical pollutants) coming from timber harvest areas; and 2) measures to protect streams, springs, ponds and other bodies of water directly by establishing stream-side management zones. The first category tells you what to do, while the second category warns you about what not to do.

Nearly 90 percent of the erosion from logging operations comes from roads laid down for access to the harvest area. Proper planning, placement and maintenance of roads are vital to prevent erosion and runoff. Before laying out roads, study a topographic map and a soil survey for your best routes. Remember that some topographic features and soil types can support a logging operation better than others. Build your roads with proper drainage in mind, and avoid wet areas if possible. Take care to install culverts, drainage ditches and turnouts where needed, and surface low areas and soft spots with gravel.

Build your road with a grade of 8 percent or less. If you need steeper grades, keep that stretch of road short. The objective is to get water off the road as soon as possible, before it picks up any great force or volume.

Road maintenance doesn't end once the logging trucks leave. Retire your road properly by installing water bars across the width of it. Water bars can be made of earth, from poles or logs cut on site, or from treated lumber and rubber belts. Whatever their form, water bars are designed to divert water from the road by interrupting its flow downslope. A water bar, properly installed at about a 30-degree angle from the main axis of the road, is very effective.

Spacing of water bars depends on the road grade. The steeper the grade, the closer the spacing. You may also want to lay down mulch and seed in open areas. This will establish green cover over bare soil as soon as possible.

Preventing sediment from reaching streams begins at the source (road beds and log landings), but you can also keep sediment out of streams by establishing streamside management zones (SMZs). Just as the grade of the road in the harvest area is important, so is the slope of the land in an SMZ. The greater the slope, the wider the SMZ. An SMZ extends at least 25 feet from each side of a stream. Within this zone you should take special care during a timber harvest. Cutting and equipment operation should be minimal. Don't allow or construct portable sawmills, log landings or skid trails in an SMZ. unless required for a stream crossing. Road building also should be minimal. If roads are required for a stream crossing, they should be constructed at a right angle to the flow of the stream. Remove treetops or other logging debris from the stream channel. If left in the stream, they can cause the stream to change course, contributing to streambank erosion and scouring of the streambed.

Using BMPs is routine practice on state-owned land. MDC employees monitor skid trails, haul roads, log landings and SMZs for evidence of excessive erosion and runoff. Timber sale contracts for MDC land now require using BMPs. In addition, every buyer who bids on state-owned timber now receives instruction on BMPs through a course offered by the Missouri Forest Products Association (MFPA). If you would like to learn more about this course, contact the MFPA.

Compliance with BMP guidelines is voluntary for private landowners, but using BMPs is in the best interest of every landowner. After all, you paid good money for your property. Why would you want to ship your best soil downstream to your neighbors by way of runoff and erosion?

BMPs undoubtedly increase the up-front costs of harvesting timber, but not using them increases the backside costs. Along with soil loss and a resulting loss of productivity, there's also the cost of maintaining roads and trails that, if left alone, will quickly wash out, forming deep, impassable gullies. Not only does this detract from the appearance of your property, it can also reduce your property value.

If those aren't good enough reasons for using BMPs, think about the quality of our water. After all, we all live downstream from someone.

This Issue's Staff

Editor - Tom Cwynar
Managing Editor - Bryan Hendricks
Art Editor - Dickson Stauffer
Designer - Les Fortenberry
Artist - Dave Besenger
Artist - Mark Raithel
Photographer - Jim Rathert
Photographer - Cliff White
Staff Writer - Jim Low
Staff Writer - Joan McKee
Circulation - Bertha Bainer