Riparian Forest Buffers

Benefit and Value runoff and sediment from the riparian vegetation also increases Riparian forests are located adjacent lands, slow damaging infiltration, which stores flood adjacent to streams (both perennial flood waters, and recharge aquifers. water and recharges aquifers. In and intermittent), and open bodies Riparian forests trap nutrients this way, damaging flood waters are of water (Figure 1). They differ and organic debris. As runoff from released slowly, maintaining stream from upland forests in terms of adjacent lands flows through a flow. Oxbow channels and adjacent topography, soils, function, and riparian forest, the water is slowed, wetlands also serve as overflow and species mix. In general, riparian allowing soil particles, nutrients, storage basins during high flows. forests are located on deep soils agricultural chemicals, and Riparian forest buffers maintain and have a more diverse species bacteria to settle. It is important for streambank stability, especially mix than the drier upland forests. sediment to settle within the forest during floods. Aerial photos taken Hydrologically, these forests filter buffer to reduce sediment loads before and after the 1993 flood in streams and the filling in Kansas showed riparian forest of lakes and reservoirs. buffers along 37 miles of the This settling process is Kansas River were responsible especially effective at for the deposition of an average reducing phosphorus in of 10 feet of soil while grasslands runoff because 85 percent and croplands lost an average of of available phosphates 78 feet and 155 feet of sediment are bonded to small soil respectively. particles. In Kansas, riparian forests Soil bacteria and fungi serve as excellent wildlife habitat break down nitrogen and and support many game and organic debris into mineral nongame species of mammals, fish, nitrate forms. These nitrates amphibians, reptiles, and birds. are absorbed by plant They serve as travel corridors roots, while other bacteria linking rivers, wetlands, and larger convert dissolved nitrogen blocks of forestlands. into various nitrogen gasses Trees provide shade, which cools that are returned to the the water flowing beneath them. atmosphere. This improves the aquatic habitat Maintaining streamside by lowering stream temperatures, vegetation is an easy and increasing the amount of oxygen in cost-effective way to the water, and reducing evaporation Figure 1. Riparian forests are located on the banks control nutrient problems from the water. Overhanging roots of water bodies and filter runoff and sediment from in streams and rivers. By and branches also provide good the adjacent lands. physically slowing runoff, fish habitat and organic inputs into

Kansas Forest Service stream systems from falling leaves and the purpose of the buffer itself. Recommended width for zone two is and small branches. This organic Given ideal conditions, buffers as a minimum of 50 feet. The purpose matter serves as the basic food little as 50 feet wide (measured from of this area is to allow the necessary source for fish and other aquatic life. the streambank) may substantially contact time between runoff and Larger organic debris, such as reduce nonpoint source pollutants the forest floor. Runoff in this zone large branches, root wads, and fallen from agricultural and urban runoff. should be sheet or subsurface flow trees also provide cover and serve In general, buffer widths should rather than concentrated flow. Zone as feeding and resting places for increase as 1) slope increases, two also provides wildlife habitat macroinvertebrates, amphibians, and 2) agricultural or urban runoff and wood production. Management reptiles. increases in amount or toxicity, in zone two should include periodic Riparian buffers are aestheti- or if 3) providing wildlife habitat harvesting and thinning. cally pleasing and provide many or recreational opportunities are The third zone is located at recreational opportunities such as purposes of maintaining the buffer the outer edge of zone two and is hunting, fishing, bird watching, and strip. called the initial filtration zone. wildlife photography. Well-managed An ideal riparian forest buffer The initial filtration zone converts riparian buffers also can provide consists of three horizontal zones concentrated flow to sheet flow. economic returns from quality along the streambank (Figure 2). Zone three is comprised of dense timber for commercial harvesting. The first zone, measured from grasses and forbs that are mowed or the top of the streambank is the grazed to recycle trapped nutrients Maintaining and streambank stability zone. The and maintain vigorous growth. Enhancing Existing purpose of this zone is to create a The minimum width of zone three stable bank adjacent to the water’s should be 15 feet. Installing struc- Riparian Forest Buffers edge. This zone provides streambank tures or grading and shaping may be Maintaining existing riparian stability and contributes organic necessary to obtain uniform sheet forest buffers is the most cost- matter and large woody debris to the flow into the riparian forest buffer. effective means of protecting and stream channel. The recommended All three zones serve a specific improving the water resources in minimum width for this zone is 15 purpose and should occur in some Kansas. An effective riparian forest feet. Management in zone one should form in an effective riparian forest buffer has easily recognizable be limited to stabilizing the banks buffer. Minimum buffer widths characteristics, including adequate and removing potential problem are strongly recommended, but width, a diverse tree and shrub vegetation. Occasional removal of narrower buffers can be managed to community, stable bank vegetation, high-value trees may take place obtain some of the benefits. a well-developed understory, deep where water quality will not be Grazing in the riparian buffer, if forest litter layers, and runoff that compromised and young replacement not excluded, should be controlled moves through the buffer as sheet trees and shrubs exist. through a combination of fencing, salt flow rather than concentrated flow. The second zone is the main placement, alternative water sources, The width of an effective riparian filtration zone and will occupy an and rotational grazing. If livestock forest buffer depends on the slope additional strip of land measured are allowed unlimited access, riparian of adjacent land, adjacent land use, from the outside edge of zone one. benefits can be greatly reduced due

Figure 2. Cross section of an ideal riparian forest to soil compaction and the loss of Table 1. Recommended tree and shrub species for riparian forest buffer understory shrubs, forbs, and grasses. plantings in Kansas. If properly managed, grazing can be a compatible use on these areas. Tree Species However, during the period of tree Baldcypress Green ash Pecan and shrub establishment, livestock access should be completely Black walnut Hackberry Pin oak restricted. Black willow Honeylocust River birch Existing riparian forests may need to be reinforced, enlarged, or brought Bur oak Northern red oak Silver maple under management to fully obtain the Eastern cottonwood Peach-leaved willow Sycamore benefits that these areas can provide. Reinforcement and enlargement can Shrub Species be accomplished through planting American plum Fragrant sumac Sandbar willow suitable trees and shrubs. Often the same results can be achieved by Choke cherry Golden currant Sandhill plum simply altering grazing practices or letting an area return to native vegetation. One of the most important steps for achieving an effective buffer is to create even sheet flow or subsurface flow through these areas. If runoff is concentrated in gullies, pipes, or tiles, it will not come in contact with the forest litter layer and vegetation, thus bypassing the whole buffering process.

Implementation of Practice In many cases, riparian forests have been cleared and converted to agricultural production. Removal of these forests has often resulted in increased soil erosion and decreased bank stability. Runoff occurs faster in converted areas, resulting in higher peak flows and Figure 3. Young riparian buffer with bank stabilization along the edge of a crop flooding downstream. As the benefits field. associated with riparian forest buffers species (See Table 1.) A typical needed to address bank insta- are better understood, landowners design recommends flood- bility (See Figure 3.) are reestablishing these areas as part tolerant species such as willow, 3. Converting concentrated flow of their overall farm conservation cottonwood, and sycamore near to uniform dispersed flow is an plan. Site-specific reestablishment the stream and more drought important factor in the estab- recommendations will depend on tolerant species farther up the lishment of an effective riparian many factors, such as adjacent land slope. forest buffer use, path of runoff, soil type, depth to 2. Plans should include bank 4. Reestablishment plans should be water table, and landowner objec- stabilization recommendations based on landowner objective, tives, but some general recommenda- if necessary. Bank stabilization such as treatment of field runoff, tions are as follows. practices and riparian forest timber production, and wildlife 1. Planting plans should contain buffer establishment are both habitat enhancement. a variety of tree and shrub Several technical and financial share opportunities, or technical References assistance programs for reestab- assistance contact the Kansas Forest Stream Restoration Specifications, lishing or enhancing existing Service, your local conservation Missouri Department of riparian forest buffers are available district office, K-State Research and Conservation. through state and federal agencies. Extension office, Natural Resources Riparian Forest Buffers: function Practices that can be cost-shared Conservation Service office, or the and design for protection include streambank stabilization, Kansas Department of Wildlife and and enhancement of water buffer planting, woodland Parks. resources. USDA., Forest management, riparian fencing, and Service. Northeastern Area, development of alternative water Radnor, PA. NA-PR-07-91 sources. For additional information Geyer W., K. Brooks, and T. Neppl. on riparian forest buffers, cost- Streambank Stability of Two Kansas River Systems During the 1993 Flood in Kansas, USA. 2003. Transactions of the Kansas Academy of Science 106(1/2): p 48-53

Deborah Goard Kansas Forest Service The Kansas Department of Health and 2610 Claflin Road Environment has provided financial Manhattan, KS 66502-2798 assistance to this project through EPA (785) 532-3300 Section 319 Nonpoint Source Pollution www.kansasforests.org Control Grant #C9007405 11.

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Kansas State University Agricultural Experiment Station and Cooperative Extension Service MF-2746 July 2006 K-State Research and Extension is an equal opportunity provider and employer. Issued in furtherance of Cooperative Extension Work, Acts of May 8 and June 30, 1914, as amended. Kansas State University, County Extension Councils, Extension Districts, and United States Department of Agriculture Cooperating, Fred A. Cholick, Director.