River Modification Regulations

Rivers have been pushed around and modified by people in North America since at least the first European contact. Beaver were trapped by European trappers until almost completely gone, causing the unraveling of thousands of miles of stream and floodplain ecosystems. Logging operations built splash dams on headwater streams across the country that would pool water and logs and then send massive floods of water and wood down streams – scouring streambeds and banks – sometimes daily. Rapids were dynamited to ease log passage. Gold Miners dredged stream banks. Farmers straightened and ditched streams based on government encouragement. Railroads and then roads for automobiles were cut along many streams – with little regard for the stream ecosystem. Dams were built. Surely you get the picture: many of the rivers that we paddle have at one time been altered by the hand of man.

That being said, many whitewater rivers in particular have recovered from these past abuses to a large degree, and have reached a new ecological equilibrium. The streambeds have been naturally reorganized by floods, the banks revegetated, and aquatic species have recolonized. Likewise paddlers have begun paddling rivers during this recovery period and have come to appreciate the existing nature of the rivers that we paddle. American Whitewater recognized long ago that river modification was a significant threat to rivers themselves as well as our enjoyment of them. In response to this recognition, AW developed a River Modification Policy.

American Whitewater developed this policy to address all types of river modifications, including those made by paddlers or for paddlers, as well as those made for other reasons that may impact paddlers. Our policy addressed both the ecological and social aspects of river modification. It should be noted as well that most significant river modifications require a permit by the US Army Corps of Engineers in order to be legal. See Section 3.5.3 of this toolkit for more information on reporting or learning more about river modifications. Below you will find our complete river modification policy as well as specific examples of river modification projects that have recently become controversial.

River Modification Guide

American Whitewater has published a technical guide offering specific considerations for designing stream modification projects in a manner that meets recreational objectives as well as primary engineering or habitat objectives. Download the document - Integrating Recreational Boating Considerations Into Stream Channel Modification & Design Projects.

American Whitewater River Modification Policy


American Whitewater's preference is for natural, free-flowing rivers, unchanged by mankind. The organization further recognizes that a controlled level of personal risk and responsibility is one of the challenges and pleasures of outdoor sports such as whitewater paddling, and that it is not desirable to remove that element of sport. However, the organization also recognizes that in rare and isolated cases, rivers are modified to reduce specific objective hazards without changing the fundamental characteristics of a rapid or to re-create hydraulic features in a previously altered river channel. American Whitewater adopts positions on proposed river modifications on a case by case basis.

Whitewater recreation opportunities nationwide, already in short supply, have been severely restricted by the widespread construction of dams, diversions, and other engineering works. American Whitewater's preferred mitigation to this damage is increased flows for recreation (and other use), improved public access, and other recreation facilities if needed. In the rare event these mitigation measures are not possible, or are not enough, construction of artificial whitewater courses may be accepted on a case by case basis. Artificial courses would only be appropriate when they would not significantly impact riverine ecosystems, existing rapids, or river use by other recreational groups.

Natural Rivers

American Whitewater opposes modifications to natural, free-flowing rivers, to rivers that have been designated as wild or scenic in the Federal Wild and Scenic River System, and to rivers which have been named by managing agencies as eligible or suitable for such designation.

Case by Case Decisions

American Whitewater views proposals for river modification with caution, recognizing that changes, once made, may be difficult or impossible to unmake and in many cases may create new and often more dangerous conditions. American Whitewater may oppose, not oppose, or endorse proposed modifications to rivers depending upon the specific needs, impacts and details associated with this action. American Whitewater may assist with planning or funding of river modifications if it endorses those modifications.


Guided by this River Modification Policy, American Whitewater will either support or not support proposed river modifications. Before choosing to endorse a river modification, the Executive Director will consult with the appropriate Committees and seek ratification by the Board of Directors.

No Harm Policy

American Whitewater will oppose proposals for river modifications unless it has reason to believe that the proposed modification will not adversely impact the enjoyment of rivers by other recreational groups and will not have a significantly adverse effect on the riverine ecosystem.

Categories of Modifications

American Whitewater considers modifications to rivers associated with recreational paddling to be for one of three purposes: for enhancing safety, improving navigability, or enhancing recreational opportunities.

Enhancing Safety

Modifications for the purpose of enhancing safety include changes that remove or reduce objective dangers, such as demonstrated entrapment hazards. A decision by American Whitewater in favor of safety modifications is more likely if (a) the modification does not change the physical or visual characteristics of a rapid, (b) the river receives a high level of use, and © the hazard in question has been demonstrated to cause drownings or near drownings. For added clarification please refer to the River Safety White Paper.

Improving Navigability

American Whitewater opposes river modifications for the purpose of improving navigability including changes to rapids that make passage of boats easier or that reduce the difficulty rating of rapids. The organization recognizes that portaging is usually an option for avoidance of specific obstacles and that advances in technique, skill, and equipment have historically made impossible rapids possible and difficult rapids routine. Presently, unrunnable or difficult rapids are tomorrow's first descents or play spots.

It is American Whitewater's position that there is a firm distinction to be made between improvements for the purpose of improving navigability and those made for reduction of objective hazards. For this reason, a proposed modification to remove a subjective hazard (such as a wave that routinely flips rafts) or to reduce the overall difficulty of a rapid is considered by American Whitewater as a modification for the purpose of improving navigability rather than safety.

Enhancing Recreational Opportunities

Modifications for the purpose of enhancing recreational opportunities range from moving a few rocks to enhance a play hole to the construction of a completely artificial whitewater race course. A decision by American Whitewater on proposed recreational enhancements hinges on the degree of previous modification of the river, the degree of terrestrial development along a river, impact of the proposal on the riverine and riparian ecosystems, and impact on enjoyment or future enjoyment by other recreational users. For example, American Whitewater would oppose modifications for recreational enhancement of a pristine, wilderness river, but might choose to endorse the construction of a play hole in a highly modified, urban river.

Artificial Structures Obstructing Navigability

American Whitewater opposes construction of structures or artificial placement of natural and synthetic materials which may interfere with navigation. These structures include but are not limited to dams, weirs, bridges, fences, and fish habitat structures. At existing low head dams, American Whitewater advocates dam removal or modification for safe passage. In cases where modifications are not possible, American Whitewater advocates availability of portage routes. For added clarification please refer to Section 24 in the River Safety White Paper.

Stakeholder Involvement and Agency Approval

American Whitewater will not endorse river modifications on whitewater rivers which do not seek public input and comment. Public comment must include American Whitewater, local whitewater clubs, and other local regional and national river recreation and conservation organizations. American Whitewater will also not endorse any river modification proposal that has not obtained the necessary managing agency permission prior to construction. In general, American Whitewater opposes river modifications made without consultation with a broad spectrum of user groups or made without agency authorization.

Examples of Paddling Related River Modification Issues:

Additional Resources

  • American Rivers has published a book on ecologically sensitive designs for the development of riverfront parks and access areas.
  • The National Park Service has published a guide to building river access areas that take ecological issues into consideration.