Water in Forested and Wild Areas

Wild lands are highly complex and multifarious, and their water systems are also very difficult to generalize about. Stream ecology and hydrology are highly dependent on local topography. Protecting water quality and riparian ecosystems are two sides of the same coin, since functioning ecologies both rely on and help create clean water.

Most streams originate in the forested uplands, be they the Rocky Mountains or the Greens. Many forested lands across the country are logged to various extents to harvest important timber resources. In order to efficiently get felled trees from the stump to the mill, loggers build roads of varying permanence through woodlands. Careful considerations must be made when building roads on forested lands. Clearing trees and exposing bare soil always runs the risk of erosion, but roads and trails are a particular risk because they often can create an avenue for water to accelerate down hills. The chief problem is erosion, which can damage hillsides and waterways, and pollute water with particulate matter and soil. The simplest and most consistent way to avoid damage is to simply not travel in particularly wet or sensitive areas. For instance, trails on Camel’s Hump are closed during mud season due to the damage caused by people trampling mud. Similarly, Vermont’s Acceptable Management Practices requires that road and trail building be laid out to minimize crossings of streams or bodies of water. The AMPs also lay out a multitude of strategies for minimizing destructive erosion. Most of these are relatively commonsense approaches to slowing water down to prevent erosion, like controls on the steepness of roads requiring water bars and culverts. Similarly, by diverting water off of roads at regular intervals, very little can build up in a given spot, and it is dispersed into surrounding forest and allowed to infiltrate into the native soil. The AMPs also pay particular attention to places where roads do cross existing streams. Truck roads must have bridges or culverts over streams, while skid trails are allowed to ford streams if the streambed is bedrock. Skid roads may also fill streambeds with slash for use as a temporary bed, but only while the ground is frozen; slash must be removed before the spring thaw.

When I visited his 240 acre woodland outside Starksboro Vermont, forester and landowner Steve Eustis said that proper water management was his first priority when he bought the property in 2005. The land has many management objectives, but high on the list are protecting water quality, maintaining biological diversity, and enhancing wildlife habitat. Among his first projects as a new landowner was a thorough audit of the roads and skid trails that crisscrossed the forested property from past timber harvesting activities. As I toured the property with him, he enthusiastically pointed out the numerous water bars he had installed too reduce erosion.

water bar

We also visited a ‘patch cut’ where 3 acres of trees had been cleared to allow for new understory development. However, the trees along a small watercourse had been left standing, despite their poor value and growth potential. Mr. Eustis stressed the importance of these remaining trees, since they help anchor the stream’s banks and shade the water, which protects the ecological structure and function of the watercourse. Forested buffers capture chemical and sediment before they reach a stream, and also rob water of momentum before it reaches the flow of the stream.

As with any land-management issue, prevention is always the best medicine, but all too often, past management, mistakes, or unexpected weather events can lead to erosion and siltation downstream. Once given a foothold, these powerful forces can quickly self-reinforce and spiral out of control. At a certain point, best practices and prevention must cede ground to active restoration. Stream restoration is a hugely broad and complex field, living at the intersection of ecology, hydrology, soil science, and engineering. All projects have multiple objectives and different ways of tackling them.

The simplest restoration is re-vegetation, particularly with native riparian species. Vegetation anchors banks and prevents erosion, and provides food and shelter for wild life both in the stream and out. Furthermore, increased vegetative cover, particularly with large woody species, can increase shade over otherwise open water. Shade is valuable since it contributes to lower water temperatures that are often more conducive to native fish and other species. If a bank is so degraded that it will not support re-vegetation, stabilization and flow disruption may become needed. If managers can introduce obstacles or complications to a fast-moving flow, water is forced to slow down, eddy, and flow in more complex patterns. Strategies like embedding root balls of dead trees into a bank or of dropping whole trees into streams help slow down water, decreasing its erosive force, and also creating habitat for fish and other in-stream creatures. Restorationists also build check dams and silt traps to prevent silt from reaching sensitive areas.

stumps

The most drastic restoration is re-grading and re-forming the channel of a stream. Streams that have become strait will stay strait if they cannot effectively break their banks and create new channels. This is often the case where rivers or streams have been artificially straightened, leveed, or ‘armored’ with stones, gravel, or cement. In these cases, it becomes necessary to create from scratch a more-natural channel. Designers often seek to allow for natural meandering and changes in precise channel location. This often means that banks are lowered and softened, and that the river is surrounded by broad stream corridors.

An important confounding factor in restoring natural stream and river conditions is the considerable dam infrastructure in place in this country. Existing on scales from a small cobblestone retention dam up to the enormous cement arches of the Glen Canyon or Hoover dams, all dams change the flow of downstream rivers. Dams often soften the variations of natural flood cycles, which can have profound implications. For instance, the Glen Canyon Dam on the Colorado River significantly disrupted annual floods through the Grand Canyon. Without the floods, a cascade of hydrologic and ecological changes occurred, resulting in shrinking sandbars, loss of vital fish habitat, and increasing encroachment by invasive plant species.

Glen Canyon dam

In 1996, the Bureau of Reclamation began a series of ‘spike flows’ in an attempt to time releases of water to mimic natural floods. The initial experiment was considered a success, as sandbars grew and trout habitat was increased. The gains were temporary, and the experimentation continues, but the point is abundantly clear; the dam has a huge effect on the hydrology and resulting ecology of the downstream community. Dams also block spawning fish from returning upstream, and divert huge volumes of water to agriculture, municipal, and industrial uses. The effects of dams on American rivers and streams are too many and too complex to delve into here. Around the country, riparian restoration efforts have sought the removal of dams and the return of natural flows.

In any case, people working to restore stream ecologies strive to allow for more wild flow and characteristics of the channel and banks. When streams are allowed or encouraged to behave naturally, their wild ecologies usually return of their own accord, and ecosystem function is restored as a consequence of intact hydrology.

-Brian


 

Sources:

Acceptable Management Practices for Maintaining Water Quality on Logging Jobs in Vermont:

http://www.vtfpr.org/watershed/documents/Amp2009pdf.pdf

Federal Stream Corridor Restoration Handbook:

http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1044610.pdf

http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1044605.pdf

UK Manual of River Restoration Techniques:

http://therrc.co.uk/MOT/Final_Versions_%28Secure%29/3.4_Alt.pdf

Skip to toolbar