Introduction to Stream Restoration - Hydro-Environmental Analysis: Freshwater Environments - page 258

FIGURE 8.41 Riprap for restoration of Pike Creek. (From Delaware Department of Natural Resources and
Environmental Control. With permission.)

The design of riparian buffers is usually based on the “three-zone” concept, where (BWM 2006):

• Zone 1: This zone is adjacent to the stream and is heavily vegetated under ideal condi-

tions. This zone is referred to as the “undisturbed forest,” where trees help stabilize banks,
shade the stream, and provide aquatic food sources. Roots, fallen logs, and other vegetative
debris in this zone slow the streamlow velocity, creating pools and habitats for macroin-
vertebrates, in turn enhancing biodiversity. Decaying debris provides an additional food
source for stream-dwelling organisms. The tree canopy, particularly in irst-order streams,
shades and cools the water temperature, which is critical to sustaining certain macroinver-
tebrates, as well as critical diatoms, which are essential to support high-quality species/
cold-water species.

• Zone 2: This zone is landward of Zone 1 and varies in width. It provides extensive water

quality improvement. This zone is considered the “managed forest,” since often the trees
are managed and harvested. This zone removes, transforms, and stores nutrients, sedi-
ments, and other pollutants lowing as sheet low as well as shallow subsurface low.

• Zone 3: This zone is landward of Zone 2, and typically consists of grass and lower-order

vegetation. This zone provides the irst stage in managing upslope runoff so that runoff
lows are slowed and evenly dispersed into Zone 2.

These three zones can be managed individually or concurrently (Figure 8.42). However, with-
out concurrent management, such as grazing management in agricultural areas, to go along with
attempts to reestablish vegetative communities, many planting operations will fail.
An initial step in the establishment of a riparian forest buffer is to determine what types of
plants will be used. A starting point is to determine what is already growing in the vicinity, where
trees growing nearby will reveal the parent material of the area and indicate what trees grow natu-
rally on that site (Palone and Todd 1997). Native riparian tree species are preferable because they
coevolved with the stream's inhabitants. The soil structure and texture, water table, soil prepara-
tion, and other factors affecting planting should be considered in the design as well as the method
of planting (e.g., using cuttings, transplanting dry root stock, and seeding) as with any horticultural
activity. The plantings in Zone 1 should be protected from disturbance. Zone 2 typically consists
of larger trees with an understory of smaller trees and shrubs. This zone can tolerate some distur-
bance and, where conditions exist, it may be planted with commercially viable species such as for