01-669-25 Me. Code R. § 6
Decay resistant species, such as hemlock, tamarack, spruce, and cedar are preferred as the key pieces of wood.
The minimum diameter required for a key piece of wood depends on the bankfull width of the stream and shall meet or exceed the requirements in Table 1.
Bankfull Width Feet | Minimum Diameter Inches |
0 to 10 | 10 |
10 to 20 | 16 |
20 to 32 | 18 |
Over 32 | 22 |
Source: Oregon - Guide to Placement of Wood, Boulders and Gravel for Habitat Restoration | |
Table 1. Bankfull widths and minimum diameter of logs to be considered key pieces.
Smaller pieces of wood should be placed in stream sections between the key pieces. The total number of pieces of wood per mile of treated stream reach shall not exceed 230. This number includes both existing pieces and pieces added during the wood addition treatment. 40-60% of these must be between 6" and 12" in diameter. The remainder must be greater than 12" in diameter.
Dispersal flow must be minimized either by placing the large wood relative to the bankfull elevation so flow passes either over or under the wood (Figures 1 (A) and (C)) or by reinforcing the bankfull sides by felling smaller trees (less than 6 inches in diameter) before the large woodis felled to protect banks from excessive erosion (Figure 2).
Figure 1. Types of flows that can be created when large wood is felled across the stream. The type of flow created by the large wood will be dependent on where the large wood is felled related to the bankfull width. If only the bottom of the large wood is within bankfull, flow will be forced under the log as shown in A. If the large wood is directly within bankfull, flow will be forced away from the large wood as shown in B. If the large wood is in or just above the summer average wetted channel bankfull flows will flow over the large wood as shown in C.
Figure 2. A) adding smaller wood on each side of the stream to concentrate flow over or under the large wood and protect banks from dispersal flow. B) over time a pool will likely form with the material moving down stream to form a pool tail/riffle habitat complex. Note this type of treatment is specifically for a stream identified by DIFW or DMR as having an over widened channel.
Wood movement is acceptable, but wood must be placed so that stable structures will eventually be formed around key pieces. Figures 3 and 4 provide examples of wood placement to form these structures. The weight of the log on the bank increases the stability and reduces downstream movement. Equipment can manipulate the logs to increase their stability by placing the wood between 2 standing trees that will lock the log in place by creating a pivot and stop point (Figure 3 panel A). In addition, one log can be placed on top of another so the weight of the top tree can pin the second tree (Figure 3 panel B). Complex structures with multiple logs with interlocking pieces of wood provide better habitat and mimic wood accumulation over time. Figure 4 provides some ideas on the configuration of the key pieces of wood in a restoration structure.
Figure 3. Panel A is single log placed between two standing trees to create a pivot and lock point. Panel B is an X pattern where the weight of the top log pins the bottom log to reduce the movement. Not shown is coarse wood (CW) or limbs that will create better habitat.
Figure 4. Showing typical plan view wood configurations and alphabet codes for use in describing them.
| Click to view image | Large wood may be positioned in the stream in various configurations. The examples to the left are some patterns that can be used. For stability, 2 of the logs must be twice as long as the bankfull channel width (1.5X if the root wad is attached) and meet the tree diameter criteria in the guidelines. Key pieces may be shorter if they can be effectively secured against movement by bracing against or between standing trees, boulders or other naturally occurring stable objects (See Figure 3). The large wood can be placed between standing trees to increase the stability by preventing the logs from rotating down stream. To increase hiding areas for juvenile fish, it is recommended that the limbs be in contact with the summer flow channel. Coarse wood can be added to the structure if the tree does not have limbs. Simple patterns can be combined to form complex structures of 3-7 logs. |
Trees felled for a wood addition treatment "count" toward the allowable removal under the requirements of 38 MRSA, §438-D (shoreland zoning) or 12 MRSA, §8867-B (statewide standards for timber harvesting in shoreland areas), as applicable.
Reasonable measures must be taken to avoid the occurrence of sediment entering the stream channel and the disturbance of stream banks. If, despite such precautions, disturbance occurs which could result in continuing sedimentation, these conditions must be immediately corrected with hay bales, siltation fence, water bars or other appropriate measures.
Wood must not be placed where downstream infrastructure could be put at risk by wood movement. A minimum of 2 meander bends must be present between the end of the treatment area and any downstream road crossing.
01-669 C.M.R. ch. 25, § 6