UCLA

Wetland loss due to human impacts is a global concern. For certain regulated activities in the United States, the Clean Water Act §404 requires replacement of aquatic functions through compensatory mitigation. In spite of the existing mitigation framework and a 2008 Compensatory Mitigation Final Rule updating regulatory guidance, concerns exist regarding the effectiveness of the compensatory mitigation program. This dissertation contributes to mitigation improvement through three studies. First, we evaluated numbers, sizes, and compensation types of §404 projects permitted before (2002-05) and after (2009-13) the Mitigation Rule to determine how its compensation hierarchy was implemented in southern California. Contrary to expectations, the proportion of third party mitigation projects, and of corresponding acres, decreased after the Rule. Within permittee-responsible mitigation, the proportion of off-site projects increased, as predicted. While is it possible the compensation hierarchy influenced these trends, external factors, particularly the national economic downturn, may also have contributed to the patterns observed. Secondly, we developed chronosequence stream restoration performance curves from projects of different ages to illustrate likely developmental trajectories of high-performing restored streams. The curves, developed using California Rapid Assessment Method (CRAM) data, predicted the time required for projects to achieve reference-level scores for the CRAM index and Hydrology and Biotic Structure attributes, but underestimated the time for projects to achieve the Physical Structure attribute reference level. CRAM-based performance curves could be used to guide standard development, and to predict future project performance. Finally, we developed an aerial imagery assessment method (AIAM) that combines landscape, hydrology, and vegetation observations into one index describing overall ecological condition of non-confined streams. Verification of AIAM demonstrated sites in good condition (as assessed on-site by CRAM) received high AIAM scores, and select components of AIAM and CRAM were highly correlated. AIAM-based time-series trajectories of three projects revealed they improved in condition after restoration, with the most dynamic change over time in vegetation characteristics. AIAM has high potential as an ecological assessment tool to determine restoration status and trajectories, and can be used for restoration management. The findings and tools produced here can improve mechanisms and methods of wetland replacement through compensatory mitigation.