Avoidance of impacts means just that; project proponents are required to take steps in the planning and design of projects that avoid impacts to natural resources. The District engages in regional master planning with avoidance in mind. The District practices avoidance primarily by leaving many unlined channels natural rather than lining them with rip-rap or concrete. Currently, approximately 127 miles of master planned flood control conveyance facilities are unlined natural washes. These natural washes help convey flood flows during large storm events.

As noted above, the District avoids construction and development of unlined natural channels where feasible. However, due to constraints such as right-of-way, flood flow velocities and other considerations, some kind of lining is required to be implemented in order to adequately stabilize flood control channels and convey the requisite flood flows.

In cases where impacts are unavoidable, the District evaluates each project to identify opportunities to minimize the impacts of a given project on the landscape. These measures include minimizing the overall footprint of the project, disturbing only areas that are absolutely necessary. 

Another method of minimization is choosing alternative channel lining approaches to be used to minimize the overall impact on the resource. For example, a channel stabilization project may utilize rip-rap (natural rock) or gabions instead of concrete lining.  In some cases this allows natural vegetation to grow throughout the lining.

When avoidance of impacts is not possible, impacts that remain after minimization measures have been implemented must be appropriately mitigated. In 2008, the U.S. Environmental Protection Agency and the U.S. Army Corps of Engineers issued a rule titled "Compensatory Mitigation for Losses of Aquatic Resources." In that rule, the agencies outlined three types of mitigation actions that can be taken to mitigate for impacts to aquatic resources: mitigation banks, in-lieu fee programs, and permittee responsible mitigation.

Mitigation banks are third-party restoration and enhancement projects that are carried out by private, for-profit entities that sell credits to the aquatic resource values obtained through the restoration and enhancement projects.

In-lieu fee programs are similar to mitigation banks, but are operated by third-party non-profit or government entities. Entities needing mitigation can also purchase credits from in-lieu fee programs. There are currently no mitigation banks or in-lieu fee programs available for credits in Clark County. The District is currently partnering with the Clark County Desert Conservation Program to develop and implement an in-lieu fee program for mitigation of unavoidable impacts to wetlands and other waters of the United States. For more information on this program, see the 2019 Clark County In-lieu Fee Program Prospectus.