The Water Tight Beaver Dam Analog

Описание: A review of a novel water-tight beaver dam analog (WTBDA) to restore eroded seasonal creeks to permanent beaver wetlands.


Authors
Christian Sorflaten, Beaver Wetland Professional, BSEE
Virginia Lagunas, Regenerative Sustainability Program, MIU
Mason Haynes, Amphibian & Reptile Expert
3/6/2022

Abstract
This study covers the design and impact of a novel water-tight beaver dam analog (BDA) developed in Iowa for settings where seasonal rains wash out beaver dams and conventional beaver dam analogs. This concept combines traditional BDA technology, mimicking natural structures that last and earthen dam science. Deep bank incision and increased drainage have created vast ecosystems where beaver dams and riparian habitat are impossible, because they get washed out. This study intends to remedy this situation and attract beaver wetland ecosystems to their historic coordinates.

Introduction
The traditional beaver dam analog has been met with much enthusiasm and success. However, it has limitations in seasonal creek areas where creeks dry out and beavers are unlikely to dam.

Hypothesis
If a water-tight beaver dam analog were constructed, it could hold enough water year round, that a beaver colony could take over maintenance of the structure resulting in a permanent and thriving wetland ecology.

Scientific Method
Identify a natural log bridge across the creek or precision-drop a tree. Pin with stakes and mimic nearby flood tolerant natural structures.
Drive vertical posts into the creek bed, supported by the natural log spillway. Scrap ash logs milled to 3”x3” and up to 9’ long were utilized. Ends were cut to point and driven in with a Titan gas powered post pounder.
Invasive honeysuckle and overgrowth cleared for wetland sun. Dormant native wetland species are expected to return.
Weave branches into BDA - beaver dam analog.
Use 4wd dump truck to deposit water tight clay plug.
Dump gravel and rocks on top of and around clay plug to prevent erosion. Fill in the area between clay plug and BDA.
Plant scrub willow and native wetland seeds into dam and bank for habitat and future beaver food.
Sand-glue willow if beaver presence is expected in a year. Water-based non-toxic glue was used. 2’-8’ willow stakes were used. Thicker, longer and straighter posts are ideal. Ends sharpened. Scrub willow is a beaver’s favorite food and gets about 15’ tall. Species vary and include red, white, black and coyote willow in the west.

Results
Water was observed to increase from 1 inch to two feet deep.
Observed fish, tadpoles and frogs grow huge in the first week.
Observed dragonflies show up in 2nd week.
Observed varieties of butterflies and moths next.
In 2-3 years, beavers are expected to arrive and maintain dam.
Tree protection and water leveling devices can be used if needed.
Mosquitoes are expected to reduce due to increased predators.
Native fish can migrate and spawn up the natural dam.
Crayish burrowed around the clay plug, through the topsoil and leaked water downstream. This appeared to not disturb the WTBDA structure.
Touch up rocks and heavier rocks may be placed around edges after heavy rainfall as needed.
Creek widening into braided channels was observed, as well as saturation of lower bank soil. Existing grasses and moss prevented erosion during high flow.
Little to no erosion was observed and sediment appeared.
Pools formed for about 100’ in both upstream forks and reached the road culvert.
Six tons of clay were used and 5 tons of limestone.
1.5 - 2 tons were comfortably loaded into 3/4 ton Chevy diesel 4WD. Mudding tires are used to reduce soil compaction.

Notes
Invasive carp theoretically cannot go up the natural dam, thereby encouraging emergent vegetation.
Beaver colonies can occupy dam complexes for well over 30 years and then repopulate years later after tree food has grown back.
Beavers mate for life and offspring will look to populate upstream and downstream areas first.
They are non-violent and build scented mounds to mark their territory.
High beaver concentration areas like the midwest can expect nuisance beavers to comb the entire area every 2-3 years, seeking out potential habitat that is rare to find.

Conclusion
The WTBDA was developed over 3 years of research and development in Iowa. Previously, we experienced BDAs washing away, beavers eating willow BDAs, undesired creek widening and everything one can imagine. It took about 2 man hours to shovel a load out of the truck, therefore a Pierce-Arrow hydraulic dump kit has been installed. A good investment for contractors, due to access to rust-proofing and regular underbody pressure washing. As with standard beaver dams, WTBDAs will work better in succession. With downstream pools touching upstream dams. We conclude this WTBDA design is suitable for any type of grant for restoration and water quality including Gulf of Mexico dead zone projects.

Sponsored by Leave it to Beavers Contracting, LLC