Role of Beaver in Riverine

Management

Marty E. Rye, P.E.Hydrologist

Superior National Forest

December 20, 2018 – MPCA Building

Duluth Urban Watershed

Advisory Committee

How do we think of beaver?As automatons or as individuals (mutes)

Need to be careful about beaver generalizations

Beaver Generalizations• Mean colony size varies depending upon setting and

conditions ~ 5.2 individuals ±1.4 standard deviation(1)

on average each colony had 0.12 non-breeding adults (2)

• Colony builds 2 to 5 dams per life cycle

• Monogamous / nocturnal

• “Mid-successional species” – prefer aspen, willow, alder, birch….can / do eat and use a multitude of other vegetation

(2) Gabel & Windels, 2018(1) Rossell & Parker, 1995

Beaver Generalizations

Beaver Reproduction - population can rebound relatively

quickly

• Litter size varies:

Midwest and south Canadian prairies ~ 4.7

North ~ 3.3

• Pregnancy frequency by age

0% kits

25% yearlings

(also reported as 40 to 54%; and only 13% in nuisance colonies)

33% 2-yr olds

60% 3-yr olds

90% older

Source: (Payne, Neil. “Population Dynamics and Harvest Response of Beaver”. 1989)

Beaver Generalizations

• Kits have a relatively low mortality

rate (protected by parents)

• Dispersal of young when 2 yrs old

• Can live to 13 yrs +

• Reproduction can replace annual

mortality rate of about 30%

Source: (Payne, Neil. “Population Dynamics and Harvest Response of Beaver”. 1989)

Beaver are an ‘Energy Source’

of Natural Disturbance

• Dam building

• Canal construction

• Browsing

Beavers Introduce

Hydraulic Complexity

• Dam Construction Changes Local Slope /

Creates Pool

• Direct Coarse / Large Wood Introduction

– Important in low energy “stable” planform systems

• Dam Failures

– Perhaps especially important in low energy systems

• Avulsions or channel realignment

• Sediment transport / substrate

Beavers Directly Introduce

Planform Complexity

Source: (Naiman, Robert. “Riparia”. 2005)

• Remnant dams can have long-lasting impacts on

the riverine corridor

Simplified Continuum Model

Upstream is steep slopes eroding banks

and channels that provide the sediment

supply to downstream reaches

Upstream Downstream

Incre

asin

g S

lop

e

Though we can think of a lot of instances

the generalized slope continuum does

not hold for localized geologic history in

Minnesota…..

• Low initial slope with a lake or wetland

as the source,

• Slope maximums at middle or lower

reaches for Red River Valley, Lake

Superior Streams, Minnesota River

Valley, etc.

(Buffington and Montgomery, 2013)

Schumm, 1977

“River Discontinuum”Headwater Forested Watersheds (with Beaver)

• Increase longitudinal heterogeneity – generating a stepped channel-bed profile in place of the continuous

slope of the reference condition,

– shallower gradients,

– slower velocities, and

– accumulation of sediment upstream of blockages, and

– scouring downstream of them.

• Increase lateral heterogeneity– maintaining upstream floodplains,

– scouring additional down-stream channels, and

– causing channel avulsions.

Burchsted etal, “The River Discontinuum: Applying Beaver Modifications to Baseline Conditions

For Restoration of Forested Headwaters”. BioScience. 2010.

Impacts of Beaver on Riverine Corridor Morphology

(Pollock et al. 2014)

(Cluer and Thorne 2012)

“Even as beaver populations continue to flourish, it must be recognized that the fluvial

landscape of modern North America is substantially different than that which was in

place prior to European contact. The beavers of North America are the reason why.”(*)

(Butler & Malanson, 2005)

(*) In addition to impacts of development on the hydrology, sediment

characteristics, hydraulics, water quality, riparian vegetation, etc. - MRye

Hydrologic Setting Impacts the

Effect of Beaver Dams

Average Annual Runoff

Hydrologic Impact of Beaver Dams

Determined by Volume

Influenced by Dam Height, Valley

Width and Slope

Steep / Narrow < Flat / Wide

Beaver will generally favor

wider lower gradient valleys (greater perimeter, lower energy to wash out the dam, etc.)

Storage Volume Based Upon Setting

Live Storage at

Start of Event

The Type of Soil Impacts:

• How Much Bank Storage

• How Much it ‘Leaks’

– Live Storage Volume

Precipitation:

• Time between events (time

to leak); so will be different

in snowmelt dominated

systems where there is a

large lag in precipitation

events after the snowmeltDead Storage

≈ Below Dam

Runout

Dead Storage Important to

Hydrologic Impact

Dead

Storage

Live Storage

Less Impact Once the Dam Overtops – Can

Pass a Lot of Water Over Wide Area

Summary of Hydrologic

Influences of Beaver• Largest impact is on smaller runoff (rainfall)

events

• Does not affect snowmelt events as much in

Minnesota due to high volume of flow and

potential frozen banks

• Beaver dams can provide local bank storage,

reduce some peak flow rates, and increase

base flow

Beaver at Lake Outlets

Dams can change the:

• Runout elevation

• Littoral vegetation

• Riparian vegetation

• Fish migration (impair)

• Outlet rating curve (how much flow at a given

elevation)

• Lake elevation

• Downstream discharge rates

Impact of dam failures – larger volume of water

Beaver Impact Water Chemistry

(Selected in One Slide)• Physically trap leaf litter from the fall

• Different (lentic) environment

• Ponds store nutrients – then when dam fails the

nutrients become available for vegetation in the new

beaver meadow

• Impacts the nitrogen, ammonium, phosphorus,

carbon, etc cycles

Beaver / Fish Interaction

in One Slide• Impacts on temperature in marginal coldwater

systems may be an important consideration

• Avery study from WiDNR*

• Removal of 219 dams on trout stream and tribs

• Showed movement across multiple beaver dams (as many as 18

dams over 4 miles)

• No improvement after 6 years

• Follow-up showed brook trout population improvement (note some

issues with design)

Beaver / Fish Interaction

in One Slide (Continued)

• Be careful about transferring conclusions – see

discussion regarding hydrologic impacts, etc.

• Best to examine information specific to the stream

being considered….

• Separate value judgements from fact

(Over 51% of studies indicating positive impact based upon data

while over 71% indicating negative impacts were speculative)

(Kemp, et al 2012)

Beaver Impact

on Riparian Corridor

• Change local vegetation through browsing

and raising the water table

• Create patches (wet meadows) that can

be sustained for a very long time

Beaver Removal to

Accommodate Human Development

• Logging – Accommodate

transportation of logs down river

system

• Transportation – Need to keep the

river transportation system clear of

blockage

• Water Power – Damming up rivers to

harness water power for mill

• Farming – Accommodate farming the

‘bottomland’ or floodplains

• Floodplain Development

Europe• Different species –

with different habits

• Being re-introduced as a ‘restoration’ tool

Source: www.beaverinfo.org

Beaver Distribution Prior to

European Settlement

Important to many Indians

• Food Supply

• Skins

Gray Wolf Range(Paquet and Carbyn,2003)

Historic Beaver Range

Influence of Wolves(1)

Population Dynamics (in Voyageurs National Park)• Wolf Beaver Kill in Voyageurs National Park

• 73% of time lone wolf

• Mean time at site to kill a beaver average of 15.4 hr (max = 48 hrs)

• Mean distance from water 10.9 m ±7.5m (2 outliers of 99 m and 222 m)

• Mean carcass utilization 98%

• “If predation is evenly distributed across colonies, then each colony likely

had approximately 2 members killed by wolves during the ice-free season.”

• “Wolf predation on dense beaver populations in a multi-prey system is

minimal and that changes in beaver population size are likely more

influenced by other factors

Behavior / Influence • Forage 100m+ when no predator

• Stay close to water when predator

(Gabel, et al, 2016)

(Gabel and Windels, 2018)

(1) Coyote, Bear, and Cougar are

also Major Predators

Beaver Trapping in the Lower USA

Historic distribution of beaver trapping in

the U.S. (Jim Sedell, U.S. Forest Service).

Perhaps 25+ million

dams prior to European

colonization in North

America…densities as

high as 10/km??

55(1) million(?) beaver in

North America prior to

European settlement

(Pollock et al. 2003)

Presently 6 to 12

million(?) beaver –

perhaps more as that

was an estimate made

in 1988.(Naiman et al 1988)

(1) Others estimate as high as

400 million beavers w/ 250

million ponds

Beaver Trapping in MN

9 Counties named after

fur traders

• Aitkin

• Fairbault

• Morrison

• Olmstead

• Renville

• Rice

• Sibley

• McLeod, and

• Brown

Fur Trading Posts 1660-1855

Source: Mn Historical Society

Beaver Trapping History in MN in One SlideSome Important Dates:1600’s Fur trading began in Mn

1732 Fort Charles established on Lake of the Woods by the French

1770’s Fur trade boomed in Mn

1783 Grand Portage Fort Built by North West Co

1784 Reference to existing Fon du Lac structure, 1793 constructed by NWC

~ Early 1800’s Steel trap introduced

1803-04 Large fires in north MN – “continual blaze” (killed beaver, but more food?)

1804/1805 Snake River Post constructed by the North West Co

1808 American Fur Company Began

1816 Fon du Lac Post closed

1825-26 Rainy River Hudson’s Bay Report – “nearly extinct”

Mid 1800’s Beaver trading posts fade (American Fur Co bankrupt in 1842)

Late 1800’s North Shore logging begins - dams would have been removed to

accommodate water transportation, changed forest structure

1901 2 Females and a Male Beaver from Canada brought to Itasca Park

1907 30 Beaver Dams in Itasca Park

1939 Trapping re-instated in 19 Counties (11,029 pelts, $121,319 = $11/pelt)

North West Co

Hudson Bay Co

(Higby, Mn Volunteer)

Beaver Pelts Prices / Harvest• Feedback loop between price and harvest.

Higher price => more harvest => more effort => Less beaver next year => more scarcity

=> higher prices => more effort ….

• Difference in business model and competition between French and English

(HBC) had an impact on the prices and (mostly Indian) harvest rates of beaver

(Carlos and Lewis, 1993)

• Hudson’s Bay Co initially limited the number of pelts at a post at a considered

maximum sustainable yield. However, suspended due to competition by the

French and NWC from the early/mid 1700’s until 1821 (Carlos and Lewis, 1993)

• Fires and disease impacted populations (Ray, 1974)

• 1859 – Hudson’s Bay Co stopped selling by pound as “demand for consumption

for hats had disappeared” (Innis, 1970)

• Some Prices:

Year $/Pelt $/Pelt (2018 $$’s) Source

1965 $20 $160.02 (Burris, 1966)

1979/80 $36.30 $126.02 HuntingPa.com

2018 $12 $12 (NAFA/ Fur Auctions / 2018 Fur Prices: NAFA February Auction Results)

Beaver Populations

Naturally Fluctuate

Over Space and Time

Source: (Naiman, Johnston, and Kelley. “Alteration

of North American Streams by Beaver”. 1998)

Likely > 0

somewhere,

sometime

“the removal of beaver from aquatic systems

should be recognized as a wetland disturbance

equivalent to in-filling, groundwater withdrawal,

and other commonly cited wetland

disturbances.” (Hood, G. A. and S. E. Bayley. 2008)

42

Beaver Impact on Humans Conflict with our service demands – most notably the

transportation system

• Failure due to loss of capacity / overtopping

• Saturation of base / roadbed

• Increased

Maintenance

Expense

• Loss of Service

• Higher Liability -

Increased Risk to

Traveling Public

Upstream Dam Failure

Dejno Creek 2018

Beaver Transportation System

Upstream Beaver Dam Failure

Crossing prior to failure

(undersized)

Fcaing downstream

Upstream beaver dam failure

Crossing Failure

66-inch CMP culvert

washed about 300 ft

downstream along with

≈ 250 cy of road fill

66-inch CMP culvert

washed about 300 ft

downstream along with

≈ 250 cy of road fill

Beaver Plugging a Railroad

Crossing in Manitoba

• “Washout, possibly due to beaver, confirmed at site of

deadly train derailment in northern Manitoba”

• September 2018 - One fatality

• “Two culverts”

may not meet

present USFS

design

standards….

Approaches at Dams / Roadway Crossings

40 in

5 ft

12 ft

7 ft

Culverts in New York

• AOP Problems

• Maintenance Further from Roadway

Flexible Leveler

Clemson Leveler

(USFWS 2015 Beaver

Restoration Guidebook)

Jensen and Curtis (1999)

MRye

• Protection from overtopping

• Cover is often an issue

(likely “undersized” culverts) - MRye

Culvert crossings

are often at valley

transitions – also

great place for a

beaver dam

Beaver Research Needs

Quantify the effects of beaver activity on the riverine

environment along the North Shore……need to

prioritize and note specific setting

• Discharge…….baseflow / anchor ice

• Temperature

• Physical Habitat

• Water Chemistry

• Biota (from mussels to moose….)

• Riparia

Beaver Roadway Crossing Issues

• Why do beaver sometimes create a dam upstream of the

crossing and other times within the crossing?

• Quantify the benefit of accommodating beaver

associated with wider crossings being installed to

meet revised design standards

• Frequency of failures due to plugging reduced increasing safety

• Life-cycle maintenance costs may counter initial capital investment

• ‘Actual’ capacity as opposed to design capacity - does it make

sense to assume an unplugged crossing in design?

• Design elements to incorporate

• Roadway embankment and culvert(s)

Beaver Research Needs

Beaver and Watershed /

Riverine Management

• Beaver are a natural and important component of the

riverine environment. A truly sustainable or restored

system must include beaver.

• They are an energy source to the morphology of the

stream and deserve the term ‘keystone’ species

• We need to understand when statements are technical

and when they are value-based

Beaver and Watershed /

Riverine Management

Human management of beaver has always occurred

and will continue. It will need to come in the form of:

Population control

Mitigation of Undesirable Effects (Design)

Modification of our service expectations

Beaver and Watershed /

Riverine ManagementBeaver need to be thoughtfully considered and explicitly

discussed in the planning and design of:

• Watershed Management Plans

• Human Infrastructure

• Roads

• Stream restoration structures / projects

• Utilities

• Floodplain use

• Resource Management Including Fisheries / Fishing

Tributary to Fawn Creek Stream Restoration

Marty E. RyeForest Hydrologist

Superior National Forest