Stream Crossings
Forestry researchers recognize stream crossings as one of the leading sources of sediment pollution associated with forestry operations. Chances are, if something goes wrong at a stream crossing, there will be a high likelihood of sediment or other nonpoint source pollution getting into the water. That´s what makes stream crossings "the hot zone!"
Careful planning can help you figure out how to handle stream crossings or determine if any are even needed. Complying with the numerous regulations that cover stream crossings and implementing Best Management Practices (BMPs) will go a long way towards protecting the water quality at your stream crossings.
Planning Your Stream Crossing
The first rule-of-thumb for stream crossings is to avoid having any to begin with, if there are other viable alternatives to get to the other side of the stream. You should examine for alternative routes that would keep your road or skid trail out of the stream corridors.
Many times, if you keep the road or trail on higher ground and away from streams, the soil is more stable and will dry out sooner after rainfall. This can allow you improved access to the property all year-round.
Locating Your Stream Crossing
If you decide that a crossing is needed, you should locate the crossing at a suitable spot along the stream. Try to situate the crossing at a location that offers these characteristics:
- Narrow stream channel width.
- Straight section of stream.
- Stable soil on stream banks.
- Relatively flat terrain at the crossing and along each approachway. This will allow you to control runoff better.
Choosing Your Stream Crossing Method
There are several different methods to cross a stream or ditch. To help choose which method you should use, consider these questions:
- Is the crossing permanent or temporary?
- What kind of traffic will use the crossing: log trucks, pickups, logging equipment, off-road/recreational vehicles?
- How frequent will the crossing be used?
- How much money do you have available to establish the crossing?
| Crossing Type | Duration of Need | Suitable Traffic | Frequency of Use | Relative Initial Cost |
|---|---|---|---|---|
| Bridgemats | Temporary | Logging tractors | Sometimes | Medium |
| Culvert pipes | Both | All if correctly installed | Often | Medium |
| Hard surface ford | Permanent | Trucks and vehicles only. No logging tractors. | Sometimes | Low to Medium |
| Permanent bridge* | Permanent | All -- Requires proper engineering and construction | Often | High |
| Pole log crossing | Temporary | Logging tractors | Rarely | Low |
| *May require state and/or federal permits. | ||||
But remember, just because a stream crossing may appear to be initially a high cost, you are always better off doing it correctly at the start and establishing a crossing that will meet your needs while optimizing water quality protection.
Chapter 6 of the North Carolina Forestry Best Management Practices Manual to Protect Water Quality provides detailed recommendations for installing a stream crossing.
For one of the more preferred temporary stream crossings during forest operations, see the reference link bridgemats.
Here are some more comparisons of different types of stream crossings to help you decide:
Bridgemats: Pros
- Can be easily used over and over at different crossing locations
- Best method for temporary crossings since all equipment is kept up & out of the water
- Quick installation and removal
- Soil disturbance of the streambank is minimized
Bridgemats: Cons
- Can be expensive to initially purchase
- Only should be used for temporary crossings
- Not suitable for crossing wide channels
- Heavy and difficult to handle and transport
Culvert pipes: Pros
- Readily available in varying lengths, diameters and materials
- Suitable for permanent or temporary use
Culvert pipes: Cons
- Requires substantial soil or backfill material to be purchased or otherwise obtained
- Can constrict streamflow if pipe diameter is not large enough, especially after heavy rains
- Difficult to select the correct diameter of pipe depending on up-stream flow conditions
Hard surface ford: Pros
- Can be used for wide crossings
- Easy to install
- Little maintenance needed once properly installed and stabilized
Hard surface ford: Cons
- Vehicles make direct contact with the water
- Cannot be used during high streamflow after heavy rains
- Only suitable for vehicles, not for use by logging tractors
Permanent bridge: Pros
- Suitable for any size stream and variable streamflows
- Can be engineered to handle most any type of vehicle or traffic use
Permanent bridge: Cons
- Can be initially expensive to construct
- Requires engineering expertise
- May require permitting
- Maintenance required
Pole log crossing: Pros
- Affordable
- Good option for temporarily crossing dried-up channels
- Easy to install and remove using typical logging equipment
Pole log crossing: Cons
- Logs must be free of soil and excessive debris
- Only good for temporary use
- Not to be used on perennial streams
- Must make sure to not block flow of stream if used in a channel with water