The City of Walla Walla is updating its Critical Areas Ordinance (CAO), found in Chapter 21.04 of the City’s Municipal Code. The CAO is a set of rules that are designed to protect environmentally sensitive ecosystems, public health, safety, and natural resources in compliance with the state's Growth Management Act (GMA).

View the draft 2026 Critical Areas Code Amendments Table (DOC, 270 KB)

Illustration of the CAO update process: Policy directive, Best Available Science, Gap Analysis, Draft Amendments, and the Legislative Process

This update is required under the GMA, which says cities must regularly review and improve their rules for protecting critical environmental areas and public safety.  The CAO update is happening alongside the update to the City’s Comprehensive Plan 2046, which guides growth and environmental policies for the next 20 years.

The City must update how streams and riparian (riverbank) habitats are classified, and new standards are required for buffer areas that protect waterways. The GMA requires cities to use the best available science (BAS) when writing rules that protect these critical environmental areas.

Key Features of this Update

  • Creation of a minimum 100-foot buffer
  • Stronger disconnected buffer provisions
  • Removal of shoreline master program regulations
  • Improved definitions

New Guidance

To support cities in this work, the Washington Department of Fish and Wildlife (WDFW) published two volumes of new scientific guidance. This is BAS that helps cities meet state requirements when writing environmental regulations.

  • Volume 1 (Science Synthesis) explains how riparian areas and watersheds affect ecological functions and fish habitats.  
  • Volume 2 (Management Recommendations) provides advice for protecting and restoring healthy riparian ecosystems, which are important for clean water, salmon, and climate‑resilient watersheds.

Riparian Management Zones

 Map of Walla Walla with 100-foot RMZs marked around waterways

 

Walla Walla is in a dryland ecosystem. Within dryland ecosystems, WDFW’s new science calls for cities to set a site‑specific Riparian Management Zone (RMZ) area with a 100-foot minimum width of existing riparian vegetation, whichever is greater. This distance is generally needed to remove most pollutants and protect water quality.

The state’s mapping tool shows where this 100‑foot RMZ should be applied. Overall, following this new BAS will significantly increase buffer width requirements for both fish‑bearing and non‑fish‑bearing streams in Walla Walla.

Diagram of dryland ecosystem, with an active river channel in the center, flanked by riparian zones, then zones of influence. The riparian zones and zones of influence make up a riparian ecosystem

The riparian ecosystem has two main parts: the riparian zone and the zone of influence. The riparian zone is the area that stretches from the edge of a stream or river up toward the higher land. This zone includes places where plants and soil are affected, at least sometimes, by water either on the surface or underground. Beyond that is the “zone of influence.” This is the area where natural processes, like plant growth and soil changes, still have a strong effect on the stream.