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.