Capitalizing on Riparian Restoration

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[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]
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Channel: SDSU Extension
Views: 2,626
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Length: 16min 24sec (984 seconds)
Published: Fri Mar 17 2023
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