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  • April

    Going Green: Restoring salmon to an urban park

    PORTLAND, Ore. -- Crystal Springs Creek is one of thousands of small streams flowing through the Pacific Northwest. Most provide ideal habitat for fish, but this creek has not supported fish passage for about 40 years. "We have accounts of salmon dating from the 50s, 60s," said Ronda Fast, Environmental Program Coordinator, Portland Bureau of Environmental Services.

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  • PUBLICATION NOTICE: The Urban Ground-to-Ground Radio-Frequency Channel: Measurement and Modeling in the Ultrahigh Frequency Band

    ABSTRACT:  Ground-to-ground radio communication and sensing within the urban environment is challenging because line of sight between transmitter and receiver is rarely available. Therefore, radio links are often critically reliant on reflection and scattering from built structures. Little is known about the scattering strength of different buildings or whether such differences are important to the urban ground-to-ground channel. We tested the hypotheses that (1) diffuse scattering from built structures significantly impacts the urban channel and (2) scattering strength of urban structures varies with surface roughness and materials.  We tested these hypotheses by measuring urban channels in Concord, New Hampshire, and Boston, Massachusetts, and via channel-modeling efforts with three-dimensional representations of the urban environment. Direct comparison between measured and modeled channels suggest that both of these hypotheses are true. Further, it appears that ray-tracing approaches underestimate the complexity of urban channels because these approaches lack the physical processes to correctly assess the power incident on and scattered from built structures. We developed a radio-geospatial model that better accounts for incident power on both directly visible and occluded buildings and show that our model predictions com-pare more favorably with measured channels than those channels predicted via typical ray-tracing approaches.

Institute for Water Resources

Pacific Ocean Division

District welcomes new tribal liaison
Nov. 14, 2023 UPDATED

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