Comparison of spawning habitat predictions of PHABSIM and River2D models*

Abstract

This study compared the predictions of two instream flow habitat models, the Physical Habitat Simulation System (PHABSIM) and River2D, with regards to spawning habitat for chinook salmon, Oncorhynchus tschawytscha, and steelhead trout, Oncorhynchus mykiss. Spawning habitat was simulated with both models for eight sites in the Sacramento River, five sites in the American River and one site in the Merced River, California, using habitat suitability criteria developed from data collected on redds in each of these rivers. For four out of five cases, both models correctly predicted that the combined suitability, calculated as the product of the depth, velocity and substrate suitabilities, of occupied locations was significantly greater than the combined suitability of unoccupied locations. There was little difference in the flow‐habitat relationships for each site and set of habitat suitability criteria predicted by the two models. The use of River2D, rather than PHABSIM, is still warranted given its ability to model complex flow conditions which cannot be simulated with PHABSIM.