Relevance

Stream environment zones (SEZ) play a variety of critical roles in the Region including natural water filtration, storage, and conveyance of surface runoff (Roby et al., 2015). Development encroaching on these areas reduces their potential to filter sediment and nutrients, and also reduces the amount of surface runoff they can effectively treat. Naturally functioning SEZs also provide open space, flood flow capacity, riparian vegetation, and fish and wildlife habitat, and buffer urban uses in developed areas. SEZ protection and restoration contributes to achievement of other environmental threshold standards, including water quality, wildlife, fisheries, vegetation preservation, recreation, and scenic resources. Even seemingly unrelated threshold standards such as air quality and noise are affected by SEZs. For instance, aspen stands in SEZs next to roadways have been shown to help physically block air particulates from spreading to adjacent areas and moderate roadway noise.

Human and Environmental Drivers

Historic logging, grazing, and direct manipulation of stream channels have impacted the functions of wetlands, streams and surrounding riparian areas. The activities degraded and reduced SEZ function resulting in decreased extent and vigour of riparian and wetland vegetation, and a reduction in the suitability of riparian and wetland areas for many wildlife species (Elliot-Fisk et al., 1996; Lindstrom et al., 2000). Ongoing restoration programs are a primary factor affecting the condition of riparian and wetland areas (Elliot-Fisk et al., 1996). These restoration projects may temporarily degrade habitat quality during and immediately following construction, but they result in a long-term increase in the extent and vigour of riparian and wetland vegetation and improved habitat conditions for multiple species. Other factors affecting the suitability of riparian and wetland areas include weather fluctuations and climate change, influences of non-native species (e.g. brown-headed cowbird or noxious weeds), and disturbance from recreational uses (Kattleman, R and Embury, M, 1996; Kondolf et al., 1996; Manley, P.N. et al., 2000).

Monitoring Programs

• SEZ Basin-wide Monitoring and Assessment Plan

Management Status Rationale

Implemented. The Region is in attainment with this management standard. Regulations are in place to protect riparian and wetland areas from permanent disturbance such as residential and commercial development, and EIP restoration projects and programs have been underway to actively expand and restore riparian areas. The TRPA Code of Ordinances implements a land capability system that significantly limits development in riparian or wetland areas and provides incentives to relocate existing development from these areas to upland areas (TRPA, 2012e). With only limited exceptions, the TRPA Code of Ordinances prohibits the manipulation of vegetation that would permanently impact riparian or wetland integrity (TRPA, 2012e). Prior to approving any vegetation management project, TRPA must consider alternatives, complete environmental review, identify mitigation measures and make specific findings demonstrating that the project is consistent with the TRPA Regional Plan and will not exceed any environmental threshold standard, including requirements for protecting upland and riparian vegetation (TRPA, 2012e). TRPA administers the interagency Environmental Improvement Program (EIP) which facilitates the implementation of projects to restore, protect, enhance and expand riparian and wetland areas.