Lower Columbia River and Estuary Ecosystem Restoration Program Reference Site Study: 2011 Restoration Analysis - FINAL REPORT

Abstract

The research presented in this report is part of the regional habitat restoration program in the lower Columbia River and estuary (LCRE). As part of this program, we have established a suite of reference sites to help meet the goal of understanding and restoring wetland habitat. The data collected at these reference sites from 2005 through the present were analyzed in this study to meet two primary objectives: 1) to inform restoration planning and design by quantifying the ecological and hydrological conditions necessary for development of wetland plant communities and tidal channel networks and 2) to evaluate the effectiveness of wetland restoration actions in the LCRE by comparing restoration and reference site monitoring data. In this report, we present the results of the analysis of 51 reference wetland sites, focusing on the elevation, sediment, and inundation ranges required by native tidal wetland vegetation. We describe critical factors influencing existing wetland patterns in the LCRE, including the vegetation assemblages present, the elevation ranges at which they occur, and the inundation dynamics that result in their current distribution. Finally, we present how these data can be used to evaluate restoration action effectiveness. v Executive Summary vi Hydro-Vegetation Zones Shallow-water vegetation assemblages show distinct differences along the gradient between the mouth of the river and the upstream end of the estuary at Bonneville Lock and Dam. There are three zones based on species richness; the central region (rkm 50 to rkm 150) has the greatest number of species, and the upper and lower ends of the estuary have lower numbers of species. These three species richness zones can be characterized hydrodynamically as tidal-dominated, mixed tidal and riverdominated, and river-dominated, moving from the mouth of the Columbia River to Bonneville Dam. We hypothesize that fewer vegetation species are physiologically adapted to the extreme inundation in the upper end of the estuary, and, likewise, few are adapted to the tidal variability and salinity in the lower estuary. The fact that the mixed zone contains the greatest number of species suggests that the natural ecological disturbance regime may be lower there, and there may be a larger species pool adapted for these conditions in this zone. This intermediate disturbance hypothesis has been used in many ecosystems to describe the conditions that result in higher species diversity. Further examination of the hydrologic gradient revealed that the estuary can be divided further into five zones, driven primarily by salinity intrusion at the lower end and stronger fluvial flooding influence at the upper end. The breaks for these zones occur at approximately rkm 40, 104, 136, and 181. These breaks are preliminary and should be refined with additional data in areas of sparse sites and with other hydrologic analyses currently under way. The five hydro-vegetation zones developed from this analysis provide a means of determining the ranges of controlling factors ...

Evidence‐based evaluation of the cumulative effects of ecosystem restoration

“…Plant community composition is a function of salinity, land elevation, and inundation (Borde et al. , Diefenderfer et al. ).…”

“…LCRE‐wide, system zonation is a function of topography, salinity intrusion, the balance of tidal and fluvial forces, and vegetation (Borde et al. , Jay et al. ).…”

“…However, wetland sites comparable to the CEERP restoration objectives for tidal freshwater and estuarine wetland habitats, including marshes, shrub‐dominated wetlands, and forested wetlands, have been monitored in recent years (Borde et al. ). As planned (Johnson et al.…”

“…To account for spatial gradients in the influence of ecosystem controlling factors on river‐floodplain wetlands, we distinguished five reaches based on Borde et al. () and Jay et al. () in CNEI calculations—an ocean‐influenced reach to river kilometer (rkm) 29, an upper estuarine reach from rkm 29 to 87, a lower tidal river reach from rkm 87 to 136, and middle and upper tidal river reaches from rkm 136 to 181, and 181 to 234 (Fig.…”

The Oncor Geodatabase for the Columbia Estuary Ecosystem Restoration Program: Handbook of Data Reduction Procedures, Workbooks, and Exchange Templates

“…Not surprisingly, questions have arisen about how to ensure data quality and standardization to provide comparable results across the CEERP (see for example Borde et al 2012). In addition, several metrics that are frequently calculated for salmon today, including density, genetics stock identification, and diet, were not detailed in the protocols ( …”