Remote Sensing and Scaling of Riverine Floodplain Physical Habitats for Estimating Potential Juvenile Salmon Production Across the North Pacific Rim

We conducted a regional classification and analysis of riverine floodplain physical features to estimate freshwater habitats for Pacific salmon across the North Pacific Rim. Riverine habitat classifications were derived at a moderate (30 m) spatial resolution using multispectral Landsat TM imagery and 90 m resolution digital terrain information encompassing the major Pacific Rim salmon rivers.  Similar classifications were also derived using relatively fine scale (i.e. ≤2.4 m resolution) satellite (e.g. Quickbird) and airborne remote sensing imagery for 31 regionally representative floodplains across the domain.  A suite of physical habitat metrics (e.g., channel sinuosity and nodes, floodplain width, proportional open water and vegetation cover) were derived at each resolution and used to assess relations between similar habitat features at different spatial scales. The results were used to assess the utility of moderate resolution satellite imagery for determining critical juvenile salmonid habitats (para and orthofluvial springs, and shallow shore) of river floodplains relative to fine scale remote sensing measurements and limited field surveys. Channel sinuosity, channel nodes and proportional vegetation cover corresponded significantly (p <0.0001) between the moderate and fine-scale floodplain habitat classifications.  Channel nodes were a strong indicator of shallow shore (R² = 0.75, p < 0.0001) and parafluvial (R² = 0.84, p < 0.0001) habitats, while maximum floodplain width was a useful indicator of orthofluvial habitat abundance (R²  = 0.53, p <  0.0001). These results were applied to the moderate-scale database to classify floodplain habitats across the North Pacific Rim. The relative abundance of juvenile salmonids in freshwater habitats was then estimated for selected catchments using the regional habitat classifications with limited fish density measurements from field-based electro-fishing data. Our findings indicate that moderate resolution global satellite imagery and geospatial data can define the spatial pattern and relative abundance of North Pacific Rim floodplain habitats with reasonable accuracy and can be used with limited field observations for regional estimation of potential freshwater production of juvenile salmonids.