Example photos and definitions of terms that may be useful for beaver dam data collection. Some measurements are also unclear in the survey and this glossary will define how those measurements are taken. There is a paper copy that can be downloaded here, this copy does not include pictures so it can print nicely. There is also a Survey123 edition of this glossary which can be downloaded to the mobile app and taken offline. However, the Survey123 edition also won’t have images. That survey is available here. You can also scan the QR code using your device for easier access.
Complex Monitoring
Active Beaver Activity: Do you see beaver or signs of beaver that indicate they are very likely still in the area and actively maintaining dams? Signs of activity can include fresh material harvest, food scraps floating in ponds behind dams.
Around Flow: Flow that goes around the dam whether that’s right at the ends of the dam or there is side channel formation.
Average Flow: Use a USGS gage if possible. Average flow is the “normal” flow, not the higher flows of runoff or the lower base flows.
Basal Flow: Basal flow describes a type of flow for water moving through beaver dams. This type of flow is when water escapes through the bottom of a dam. Not to be confused with base flow.
Base Flow: This is the minimum flow of a river and is a result of groundwater seepage rather than runoff. Not to be confused with basal flow.
Beaver Dam: A beaver dam is a dam built by beaver these can be small secondary dams that may be as little as a couple feet across or larger primary dams which can span huge lengths.
Beaver Dam Analogue: A manmade structure built to mimic a beaver dam, these can be built with posts or postless. The first image is a postless BDA while the second has posts.
First photo by Ally Smith, second photo by Wally Macfarlane.
Beaver Dam Complex: A series of beaver dams, typically a mix of primary and secondary dams. The left image has red lines to indicate the location of dams, the right is the image as it was taken. The bottom image shows a primary and secondary dam as well as a lodge.
Photo by Nick Weber
Blowout: A dam blowout is catastrophic damage to the dam. This dam holds back very limited water because so much has been knocked out.
Breach: This is mild damage to the dam so that it doesn’t hold back all water but isn’t completely broken away.
Dam Crest: The top edge of a dam.
Photo by Ally Smith
Dam Height: Measured from streambed on the downstream side to the dam crest.
Dam Notching: This is an act that beavers perform where they lower the crest elevation of their dam or remove part of the dam to drain their pond to clear out old material so that it can refill with fresh water. Similar to draining a bathtub
Food Caching: A pile of bark, twigs, and leaves that beavers use as a winter store of food. This is usually found in the pond behind a dam.
Freshet: High flows because of heavy rain or melting snow.
Historic/Relic Beaver Activity: Do dams in the area appear to have been blown out for more than a year? There aren’t signs of beaver activity at all? There isn’t much food around, and it would take a substantial amount of beaver power to reinhabit? This is what historic beaver activity looks like.
Inactive Beaver Activity: Is this an area that looks hospitable to beaver, dams are present but maybe not as maintained, and with minimal work a beaver could move back in? That means it is inactive.
Lodge: There are two types of lodges beavers can build. One is a bank lodge and the other is what you might typically think of when you think of a lodge. A typical lodge can be found in the large pond that forms behind a primary dam. Bank lodges are close to the bank and include tunnels dug through the bank.
Material Harvest: Evidence includes freshly felled trees with a pile of wood shavings around the cut. Felled trees may have smaller branches plucked off by beaver and willow in the area may be coppiced.
Photos by Jay Wilde, Joe Wheaton
Over Top Flow: This is flow that cascades over the top of a dam like a waterfall.
Primary Dam: The largest dams in a complex, these dams usually extend onto the floodplain and create the ponds beaver place their lodge in.
Primary Water Surface Drop: Measure the elevation difference between the primary pond water surface behind the dam and the water surface directly downstream of the dam and pond.
Skid Trail Usage: Skid trails are little paths of packed down grass or compacted dirt or mud that beaver use to drag materials into the pond.
Photo from: Beaver Ecology and Relocation Center
Secondary Dam: Smaller dams that typically span only the active channel and not extending onto the floodplain, these dams create smaller ponds that allow beaver to travel up and downstream in safety.
Scent Mound: Otherwise known as a castor mound, these are piles of mud around beaver ponds that are used to mark territory. Beaver secrete castoreum from a gland onto these piles. The scent has been described as a musky vanilla or leathery.
Through Flow: Through flow is water that passes through a dam to the downstream side.
BRAT cIS
Age of Activity: Assessing age of activity will rely on looking at how old the chewed wood looks. When beavers chew trees down they usually leave a pile of wood chips behind. Both the color of these and the stump of the tree can be used to estimate how fresh a cut is. Another sign of activity can be how intact and maintained the dams look or by the food scraps floating in a pond, whether those scraps look freshly debarked or not.
Anabranch: Branches from the main stem of the river that rejoin the river downstream.
Backwater: Backwaters are where the water is delivered by back flow as a result of some downstream channel restriction rather than being delivered by the current of the river.
Blowout: A dam blowout is catastrophic damage to the dam. This dam holds back very limited water because so much has been knocked out.
Breach: This is mild damage to the dam so that it doesn’t hold back all water but isn’t completely broken away.
Channel Setting: This dropdown in the survey asks about what type/which channel of the river you are in and currently assessing capacity for.
Ephemeral: A stream that only flows when there is a storm/runoff event that feeds it water. These usually dry up shortly after the event.
Food Caching: A pile of bark, twigs, and leaves that beavers use as a winter store of food. This is usually found in the pond behind a dam.
Intermittent: Streams that flow for some time after run off but not year round, these dry up or have disconnected residual ponds at some point in the year.
Material Harvest: Evidence includes freshly felled trees with a pile of wood shavings around the cut. Felled trees may have smaller branches plucked off by beaver and willow in the area may be coppiced.
Photos by Jay Wilde, Joe Wheaton
Perennial: Perennial streams flow year round, without drying up during the year.
Potential for Conflict: The likelihood that beaver dam building will impact human infrastructure or the adjacent human landscape, activities include: roads, culverts, manicured landscaping, farming, potential for flooding of infrastructure, etc..
Proximity to Expansion Zone: This metric is one that evaluates the potential for the expansion of the beaver’s range. As beaver reproduce and the colony grows the older kits will be dispersing into the broader area.
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