Effects of changing patterns of forest and impervious land covers on hydrologic regimes of watersheds were evaluated for urban and rural areas of the lower Cedar River drainage near Seattle, Washington. Land cover characterizations were used in a spatially explicit hydrology model to assess effects of land covers on watershed hydrology during presettlement conditions ("full forest cover"), 1991 and 1998. For the presettlement to 1991 period, urban watersheds showed decreases in forest covers (range 63% to 83%) and increases in impervious surfaces (range 43% to 71%). Rural watersheds showed similar patterns but smaller changes, with forest covers decreasing (range 28% to 34%) and impervious surfaces increasing (range 8% to 15%). For the 1991 and 1998 period, changes in forest covers for urban and rural watershed were <24%, with losses in some watersheds and regeneration in others. Impervious surfaces continued to increase, but increases were larger in rural (range 38% to 60%) than in urban watersheds (range 4% to 27%). Flood-frequency curves indicated that discharge rates (m sec(-1)) for all watersheds were higher in 1991 and 1998 than historical and suggested that chances for floods increase because of changing land covers. The largest increases in discharge rates were in urban watersheds, with rates for 2-year, 10-year, and 25-year recurrence intervals being more than two times greater than the rate during historical conditions. Changes in flow regimes were indicated by presettlement discharge levels of less frequent recurrence intervals (10-year and 25-year) occurring in posturbanization times (1991 and 1998) during more frequent intervals (2-year and 10-year). Normalized flows (m yr(-1)) of watersheds for 2-year, 10-year, and 25-year recurrence intervals indicate how flow regimes in 1991 and 1998 can change as functions of different areas of land covers. During 1991 and 1998, abrupt increases in flows occurred when forest covers were low (range 17% to 37%) and impervious surfaces were >46%. In contrast, the lowest flows occurred when forest covers were most extensive (range 59% to 81%) and impervious surfaces were <23%. We conclude that our use of spatial characterizations of impervious surfaces and forested covers in a spatially explicit hydrology model provides a robust approach for revealing how variations in different types and spatial distributions of land covers can affect flood regimes and flows of different watersheds.

A spatially explicit linear, additive model was developed for quantifying site characteristics of riparian areas of the lower Cedar River, Washington, USA. The spatial complexity and distribution of combined habitat and anthropogenic landscape features were used to define habitat "indices" that indicate the relative quality of riparian habitats. Patches of contiguous grid cells were measured in terms of their locations, sizes, and relative degree of fragmentation. Additionally, intrapatch heterogeneity was measured to identify unique combinations of habitat and anthropogenic factors for individual grid cells within patches. Model verification indicated that existing floodplain riparian habitats received positive indices more than 90% of the time. Mean patch sizes and fragmentation indices were similar for all positive indices throughout the reaches in the valley floor. Among all reaches, reach 7 had the highest number of positive patches due to a higher degree of meandering in this reach. This procedure and model outputs provide unique screening opportunities for prioritizing management of riparian areas (e.g., conservation, restoration and enhancement).

Strategies for protecting and restoring riparian and stream ecosystems commonly encounter uncertainties about natural processes and management practices that contribute to environmental disturbances. Improvements in management plans require landscape approaches that account for the explicit spatial distribution and variability of different land cover types that can contribute to unstable conditions. We use a spatially explicit procedure to determine erosion-risk indices and variable riparian buffer widths in watersheds. The indices are based on land cover types that can contribute to erosion either alone or collectively. Land cover information (e.g., unstable soils, immature forest stands, roads, critical slope for land failure and rain-on-snow areas) was used to estimate erosion-risk indices. Erosion-risk indices increase with greater co-occurrences of contributing land covers. The procedure was used to identify erosion-prone areas in tributary watersheds of the Beckler-Rapid River drainage (260 km2), in the State of Washington, USA. A Aquatic Sciencesregression analysis of the relationship between mean sediment inputs to streams and erosion-risk indices of sixteen different watersheds indicated that erosion-risk indices explained 65% of the variation associated with sediment inputs to channels. Landscape maps of erosion-risk categories, based on ranges of erosion-risk indices, allowed spatially explicit definitions of stream reach lengths susceptible to different levels of erosion. Low to high-risk categories, and reach lengths vulnerable to erosion, also permitted the identification of the distribution of channels requiring protection by variable riparian buffers widths. The applicability of the procedure to other landscapes was demonstrated by estimating erosion risk-indices and variable riparian buffer widths for watersheds in the upper Cedar River drainage near Seattle, Washington. This approach allows watershed managers to use existing records and published information to address environmental problems within highly variable landscapes.

We used field‐surveyed and digital elevation model (DEM) parameters to predict density distributions of juvenile coho salmon Oncorhynchus kisutch and Dolly Varden Salvelinus malma in remote streams on Prince of Wales Island, southeast Alaska, and to identify influences of associated reach‐level habitat characteristics. Fish densities were highest in two reach types (low‐gradient floodplain reaches and moderately contained reaches) characterized by numerous pool habitats, low pool spacing distances, and abundant large woody debris. Regression analyses indicated that channel gradients measured during field surveys (M‐gradients) accounted for significant amounts of the variance in coho salmon and Dolly Varden juvenile densities. The DEMs derived from a 2000 space‐shuttle radar mapping mission were used to estimate channel gradients (DEM‐gradients) and gradient zones: (0–3, >3–6, >6–15, and >15%) in stream networks. A high correlation between DEM‐gradients and M‐gradients (r = 0.92), along with the regressions of M‐gradient and fish density, provided a template for comparing DEM‐gradient and M‐gradient predictions of fish densities within gradient zones of the watersheds. Juvenile coho salmon and Dolly Varden densities (number/100 m2) predicted from the DEM‐gradients and M‐gradients were consistent for a majority of the gradient zones. Our results and expanded analyses should facilitate development of paradigms for assessing fish distributions in remote landscapes.