Where do you put straw wattles?

Straw wattles, also commonly known as contour straw wattles, straw tubes and straw worms, are used near construction projects, in ditches and in other areas with a significant slope and inadequate vegetation. They reduce erosion, increase filtration and retain soil for one to two years, making them ideal for temporary protection while permanent vegetation becomes established. Proper installation of straw wattle helps to ensure it remains stable and is able to control erosion at its site for an acceptable length of time.

1. Mark locations to place straw wattle, using wire flags, small stakes or sticks, while locating and following an imaginary line that remains at the same elevation. Use a hand level to ensure you remain on level ground. The straw wattle should be perpendicular to the slope. Plan for a slight downward angle at the end of each row of wattling to stop water from pooling in the middle of the row. In a sloped area large enough to require multiple lines of straw wattle, spacing depends primarily on the slope's steepness. In an area with a 1-to-1 slope gradient, or a 1-foot vertical change per 1 foot of horizontal distance, for example, plan to space wattle rows no more than 10 feet apart. If an area has a 4-to-1 slope gradient, or 1-foot vertical change per 4 feet of horizontal distance, plan to space rows of wattle about 40 feet apart. Where soil is soft and loamy, plan to space the wattle rows slightly closer together. You can leave more space between wattle rows if the soil is hard and rocky.

2. Dig a shallow trench along each location you marked. If the soil is hard and rocky, make the trench 2 to 3 inches deep. If the soil is soft and loamy, dig a trench 3 to 5 inches deep.

3. Lay straw wattle in each prepared trench so that it is solidly in contact with the soil on the trench's bottom. Where more than one wattle is needed to complete a line, ensure that the ends of the two sections of wattle touch each other tightly.

4. Pound a wooden stake into each end of each wattle and every 4 feet in the middle of each wattle. Each wooden stake should be 18 to 24 inches long and either 2 by 2 inches or 1 by 2 inches wide. Angle the stakes so they are perpendicular to the soil surface, and drive the stakes at least 6 inches into the ground, leaving 2 or 3 inches of each stake visible above the top of straw wattle.

5. Pack the soil you removed to dig the trenches along the uphill side of straw wattle, tamping it with your foot. The packed soil keeps water from flowing under the straw wattle.

What are Contour Straw Wattles?

Straw Wattles, also known as straw worms, bio-logs, straw noodles, or straw tubes are man made cylinders of compressed, weed free straw (wheat or rice), 8 to 12 inches in diameter and 20 to 25 feet long. They are encased in jute, nylon, or other photo degradable materials, and have an average weight of 35 pounds. They are installed in a shallow trench forming a continuous barrier along the contour (across the slope) to intercept water running down a slope.

When are Contour Straw Wattles Used?

Straw Wattles are used on burned slopes that have less than 30% of the original ground cover remaining and are at risk for increased erosion. They can be installed on slopes up to 70 percent, however their effect diminishes greatly on slopes steeper than 50 percent. Soils can be shallow, but not less than about 8 inches. Straw Wattles increase infiltration, add roughness, reduce erosion, and help retain eroded soil on the slope. Straw Wattles should be effective for a period of one to two years, providing short term protection on slopes where permanent vegetation will be established to provide long term erosion control. Contour Straw Wattles accomplish the same treatment as Log Terraces, but require less skilled labor to install and can be placed on the slope more effectively. Straw wattles should not be placed across drainage swales and channels with more than 2 acres of contributing drainage area because they are not sturdy enough to resist the forces of concentrated flows.

What Materials are Needed?

• 9 -12 inch diameter tubes, 10-30 feet long
• 5 - 1x2 or 2x2 wooden stakes, 18 - 24 inches long per wattle
• Hand tools -shovels, polaskis, & stake hammer
• Small machines may be used for plowing trenches on 30% or flatter slopes

How are Contour Straw Wattles Installed?

• Layout a contour line on the slope with a hand level and wire flags.
• Dig a shallow depression (about 3 to 5 inches deep) and lay the wattleinto it.
• Drive a 1x2 or 2x2 wooden stake through the center of the wattle at least6 inches into the ground, stopping about two inches above the wattle.
• Put 5 stakes in each wattle, installing them end to end in the trench.
• Seat the wattle with foot tamped backfill on the upstream side such thatwater flowing down the slope will not run under it.

How Many Straw Wattles Are Required?

The horizontal spacing of straw wattles on the slope is determined with consideration for normal rainfall intensity, slope steepness, soil characteristics, and the extent of surface cover remaining after the fire. Figures 1 depicts the placement straw wattles on the slope. Table 1A and 1B show recommended spacings for treating burn areas within the June 2000 HI MEADOWS and BOBCAT Fires in Colorado

FIGURE 1 - Typical Straw Wattle Installation

Tables 1A, 2A, 3A - Recommended Spacing for Contour Straw Wattles based on Burn Severity - Hi Meadows Fire Area

Tables 1B, 2B, 3B - Recommended Spacing for Contour Straw Wattles based on Burn Severity - Bobcat Fire Area

NOTE: After a fire many trees are weakened from burning around the base of the trunk. The trees can fall over or blow down without warning. Shallow rooted trees can also fall. Therefore be extremely alert when working around burned trees.

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