[Introduction Music] Streams and rivers are often referred to as the lifeblood of
the land. A few places make this more apparent than the Arid and semi-arid portions of the western
U.S. For a brief period that may only last a few weeks a year there is enough water for life to
flourish here turning vast expanses of rangeland into a sea of green. During the remaining
time streams and their riparian areas are the primary source of water emerald green lines
and a land that is dominated by browns and yellows. The dense vegetation of riparian areas helps to
trap sediment and pollution that is transported by overland flows during rain and snow melt. This
decreases soil erosion and helps to improve water quality. During high flow events the vegetation
helped to slow water that escapes the string banks. This water can then deposit its excess sediment
and nutrients while some of it infiltrates into the soil. This allows riparian areas to act as a
sponge absorbing water during weather conditions then slowly releasing it back into the stream
as conditions dry. The water and nutrients that are absorbed promote the growth of denser more
luxuriant vegetation like that seen in the photo on the left. The photo on the right shows just how
severe the contrast between dry sparsely vegetated uplands and wetter riparian areas can be. Slowing
stream flow and encouraging the movement of water into the soil can lessen the energy of the
stream. The dense riparian vegetation can help trap debris that would otherwise clog road culverts
and irrigation structures downstream. You can see in the picture on the right that downed trees and
branches were caught in the riparian area during a past high water event. By doing this, riparian areas
can help to reduce downstream damage from flooding. Despite making up less than two percent of the
western landscape, riparian areas can account for up to 20 percent of available forage and in some
area as much as 80 percent of forage consumed by cattle. The allure of riparian areas goes beyond
just applying more abundant vegetation and water, however, taller grasses and Woody vegetation that
grow in many riparian areas can also provide protection from the sun during the heat of the
summer and shelter from the wind and blowing snow during winter. Of course livestock producers aren't
the only ones that benefit from riparian areas, an arid and semi-arid regions up to
80 percent of wildlife species also rely on repairing habitat at
some point during their lives. The vegetation here is especially attractive
to insects and arachnids and for pollinator species riparian areas can represent one of the
earliest and longest lasting sources of food. The abundance of food and shelter also draws
species that are typically associated with upland habitat such as sage grouse and pheasants
for sage grouse proximity to riparian habitat is a significant predictor of breeding sites and is
often crucial to the survival of their young. In addition to the benefits of food, water and shelter
riparian habitat also serves as a corridor for wildlife travel. From tiny insects and rodents to
elk and moose, riparian corridors provide habitat connectivity for species that would otherwise
find themselves restricted to isolated pockets. These benefits to wildlife can also benefit
landowners areas managed with wildlife and mind can be used for the recreational enjoyment
of family and friends or be utilized to diversify income through fishing and hunting
opportunities or through agro and ecotourism. The demands placed on streams and riparian
areas have had their effect though. Historical land use changes in precipitation regimes
and prolonged drought have caused many streams to become degraded. This is a seasonal creek
on public land in Northwestern South Dakota you can see the results of natural salt
deposits combined with the changes to water management and land use within the watershed.
Repeated wetting and drying has caused salt to leach upwards and migrate into the riparian
area with water as it flows from the uplands. The heavy accumulation of salt has led to a shift
in the vegetation community which was compounded by heavy trampling from cattle. You can see how
sparsely vegetated the floodplain is with many of the remaining plants being either distasteful
or poisonous to both livestock and wildlife. This picture is located just a few hundred
meters downstream where the lack of vegetation and structure have allowed the creek to dig
into its own bed. The incision here is so bad that riparian vegetation can only exist for
a meter or two around the pool before water becomes too difficult to reach. You can see that
the salt is beginning to accumulate here as well and the trampling by cattle trying to reach
the pool to drink is causing the incision to spread. Streams like this are common throughout
the Northern Plains traditional restoration to repair damage like this is often costly, invasive
and heavily regulated which makes it prohibitive for many landowners whose time and money
are limited. This has led to an interest in alternative restoration methods that can
be effectively used by private landowners and small groups while still being able to
be scaled up to larger restoration efforts. Among the most popular restoration methods that
arose are what are referred to as process-based restoration. These methods rely on natural
stream processes rather than forcing streams into a desired state that may or may not be
sustainable. These methods are varied and are based on the work of many different
practitioners in a multitude settings. South Dakota State University, the Nature
Conservancy and the NRCS set out to find process-based restoration methods that
were cheaper than traditional methods minimally invasive and which could be
used by private landowners with minimal expertise and permitting. Collectively we
refer to these as low-cost low-tech tools. Part of this research looks at channel
spanning structures such as beaver dam analogs and post-assisted log structures
or BDAs and Pals for short. We believe that these structures could have significant
effects on the soil moisture forage production and plant community structures
of riparian areas in the Northern Plains and that they can be used to the advantage of livestock production.
Mediation pals are simple structures built from local materials such as downed tree limbs live
cuttings from riparian species sod mats and rock. Depending on the site untreated posts are often
used to anchor the structures in place though some projects may be able to use local materials
for post as well or do without posts altogether. These structures are not permanent and
generally only last a few years before needing repairs or replacement. During planning
sites that offer additional anchor points such as larger downed trees, boulders or root wads on
the stream bank are often chosen for structures in order to increase their durability. To further
improve their effectiveness multiple structures are placed so that the effects of the
structures becomes cumulative and the failure of any single structure is unlikely to
cause a failure of the restoration as a whole. In 2022 foresights were selected from headwater to
medium-sized streams in the 60A and 63A major land resource areas to maintain a degree of similarity
in the ecology, geology and topography of our sites. Among our sites was the lower reaches
of Cottonwood Creek on the South Dakota State University Cottonwood Field
Station near Philip South Dakota. The Cottonwood Research Station is
a roughly 2 500 acre active cattle producing operation where SDSU researchers
and students perform applied research into animal nutrition, grazing management
rangeland, ecology and riparian restoration. There are almost six kilometers of Cottonwood
Creek on the Research Station. Despite being a mid-sized prairie stream that drains hundreds of
square kilometers, Cottonwood Creek is ephemeral. Most of the creek on the station is incised
from one to three meters and it is completely disconnected from its historical flood
plain during all but the worst flooding. Further complicating matters two segments of
the creek were straightened at an unknown time in the past this led to increased flow velocity
and erosion during high water and has made the area's downstream even more unstable. Inset
floodplains have formed in many parts of the creek but its flashing ephemeral flows mean that
most of them only last for a few years before being scoured away. Because of this, the inset
floodplain has few trees or shrubs. Historically there was a beaver population here but they were
not active on all parts of the creek during most years and they were trapped out entirely in
2019 to facilitate cattle production. Beavers remained on the property's up and downstream
but were only transient within the station. The site that we selected on Cottonwood Creek
was located on the downstream end of the station. The site was broken into six experimental
reaches three each of control and treatment. Each reach was a little over 70 meters long or
roughly the equivalent of 20 bank full stream widths the control reaches were located on the
southern upstream portion of the site and were separated from the treatment reaches by two reach
equivalents to minimize the effects between reach types. Within the control and treatment sections
of the site individual reaches were separated by at least one reach equivalent. Like most of the
creek on the station this section didn't flow during most of the summer though there was often
water in the last two to three hundred meters. Despite signs of beaver on nearby properties, signs
indicated it had been several years since they had been present here. Because of the nearby beavers,
and the severity of stream incision here which would require long-term maintenance reassessment
and construction of new BDAs and Pals to fully treat it was decided that the primary goal
for this site was to bring back the beavers and let them do the work for us. Unfortunately,
despite signs of nearby activity the nearest known active dam was kilometers away and the
beavers preferred food sources were located on the terrace of the stream which was over two
meters up a steep bank in most of this area. Because of this, we anticipated it would
take a few years for them to return. This was the nearest beaver dam
known to be frequented by beavers it was separated from our test site
by over three kilometers of stream. When we looked at this dam during site selection
in Spring of 2022 it was over two meters tall on the downstream side and almost completely
impermeable to water. According to the station staff it had been there for years and all efforts
to remove it by hand had been abandoned. We believe that this dam which was constructed largely of
clay from the stream bed and banks had dried out as water levels in the creek dropped causing it
to lose much of its structural integrity. On August 26th about a month after our structures were built
a storm dropped 20 millimeters of rain in a day. The picture on the left shows what was left of
the dam shortly after this rainfall. It appeared that the sudden influx of water had caused
it to fail completely in a matter of seconds. Mud deposits and vegetation left downstream showed
that the resulting surge of water peaked at almost two meters above the previous water level even
three kilometers downstream. A search of the creek a few months later found the remains of an old
beaver dam that are shown in the picture on the right this area had no signs of beaver activity
in recent years and the creek here had not been examined during site selection. If this dam was
still standing but in a state of disrepair when the other dam breached it would have only added
to the damage downstream when it too failed. The flood destroyed or severely damaged over
half of the structures that we built. This was the largest structure that we created on Cottonwood
Creek and the one furthest upstream that was left intact After the flood it was anchored into
the Upstream side of a downed Cottonwood in order to reinforce it. For reference the top
of the Cottonwood log is a little less than two meters above the stream bed. You can see how
much debris it collected during the flood down branches, fence posts, and the shattered remains of
the structures from upstream all came to rest here. The original structure is no longer visible and
the accumulated material has almost doubled its height. This structure served its purpose better
than we could have ever anticipated. Slowing water so the four structures downstream
also survived intact and backing water so the structure immediately upstream was only
slightly damaged during the initial flood surge. It also allowed something that we hadn't
anticipated at least not for a few years. Within a few days newbie resign was seen in
the area for the first time since beavers have been trapped out. Newly cut and trees were found
even in areas where the creek was deeply decreased in size. Just a few meters downstream from our first
experimental reach a roughly 70 centimeter tall dam now spanned the creek. The effects of the
single dam exemplify what we sought to mimic with our BDAS and Pals before our structures were
installed in July you can see just how low the water in the creek was despite having over
70 millimeters of rain in the previous month. By mid-august, dry conditions, and a lack
of return flow had lowered Creek levels to the point of the Cottonwood Creek no longer
flowed. Any remaining water was in a series of disconnected pools that were rapidly shrinking
in the summer heat. You can see our structure in this image but by the time this was taken
there was almost no water left Upstream of it. Then the storm on August 26 happened you can see
where the beavers built their new dam and formed a pond. With low stream gradients on Cottonwood Creek
this one dam backed water for over 200 meters. Not only did the new beaver dams slow the
water and cause it to back up unlike the beaver dam that had breached this dam was
still permeable to water. You can see in this video how the water level below the
dam is almost equal to the pond above it. Recolonization or reintroduction of beavers is one
of the major goals for many restorations utilizing BDAsand Pals it was the primary objective for
the Cottonwood Creek site but because of the severity of the stream incision and lack of woody
vegetation throughout the inset flood plain it was expected to take two or three years for beavers
to return. Thanks to an unexpected disaster, we achieved this goal in a little over a month. As
is often the case humans who had to adjust to fit new realities imposed by nature. The recolonization
of one of our experimental reaches by beavers has required adjustment to the original plan for
this site. Because of the significant effects beavers can have on vegetation and stream
morphology that BDAs and Pals do not, this site can no longer be treated as equivalent
to the other sites in the study instead the Cottonwood site is now being treated independently
of the other sites and will be integrated into future projects researching other aspects of
restoration utilizing BDAs, Pals and beavers. Riparian areas are a key part of the
western landscape they are crucial to livestock and wildlife that depend on them
for survival during part or all of the year. They act as a sponge that can absorb and
store water and in doing so can help to mitigate the effects of fire, flooding and drought.
Unfortunately, historic land management practices and changing water regimes have degraded many
streams throughout the world. Low-cost low-tech tools such as beaver dam analogs and post-assisted
log structures rely on natural stream processes to restore riparian areas and reconnect floodplains.
They are becoming increasingly popular due to their relative ease of construction and the
ability to implement them at a variety of scales. These structures have been shown to have positive
effects on stream and riparian health in several areas of the western U.S., but have only recently
been tested in the Northern Plains. Despite their temporary nature, these structures can continue
to improve stream and riparian habitat even after the structure has technically failed. In the
case of Cottonwood Creek, despite losing half of our structures BDAs and Pals encouraged beavers
to recolonize a portion of the stream that they had been absent from for years turning what
was otherwise a disaster into an opportunity. We would like to thank our project partners at the
Nature Conservancy and NRCS. Special thanks to Lori Brown with the Nature Conservancy and Mitch
Faulconer with the NRCS Belle Fourche office. Primary funding for this research was
provided through the North Central SARE program. Partial funding was
provided by the Nature Conservancy through the Nebraska chapters J.E
Weaver Competitive Grant Program. [Ending Music]
