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UBC Theses and Dissertations

A GIS evaluation of land use dynamics and fish habitat in the salmon river watershed - Langley, B.C. Watts, R. Dean


With increased urban development in the Fraser River Basin, it is expected that fish habitat degradation will become more widespread bringing into question the sustainability of the fisheries resource. This thesis examines the dynamics of land use and fish habitat in the Salmon River watershed located in the Lower Fraser River Valley. The study was initiated to:1) quantify the distribution and recent trends in land use changes; 2) identify and quantify critical fish habitat to provide a basis for assessing habitat deterioration in the future; 3) characterize recent fish habitat changes; and4) describe trends and processes associated with fish habitat and streamside land use relationships. Geographic Information System techniques were used to analyze the land use data and to display the results. The distribution and temporal changes in land use from1979-80 to 1989-90 are examined in three ways: 1) an evaluation of overall watershed conditions; 2) an evaluation of a 500 meter buffer zone of the stream network; and 3) an evaluation of 500meter buffer segments of four key fish habitat reaches. A significant decrease in agriculture, a substantial increase in undeveloped areas, and a modest increase in residential development were measured over the 10 year period for both the overall watershed and the stream network buffer. Similar land use trends were observed for the four key fish habitat buffer segments. A large increase in residential development was particularly notable in two of the four buffer segments. Stream morphology characteristics were measured in prime fish habitat areas of the Salmon River, and its principle tributary Coghlan Creek. The fish habitat was classified into four hydraulic unit types; riffles, glides, pools and sloughs. A comparison of reaches between the two streams showed that the Salmon River had twice the stream volume relative to Coghlan Creek. The reaches selected for study within the two streams are considered the most critical spawning and rearing areas for salmonids in the basin. Measurements of preferred hydraulic habitat for salmonids (riffles, glides and pools) showed that Coghlan Creek had 20% more high quality habitat than the Salmon River. A interesting 2:1 relationship was found between reaches in the Salmon River and Coghlan Creek for both stream volume and smolt catch numbers. This ratio was consistent for five years between 1979 and 1989 for which reliable data is available. However in 1990 and 1992, smolt catch statistics decreased by half in the Salmon River which coincides with significant increases in urbanization. More information is needed to document these trends and to provide evidence for cause and effect relationships. The techniques used in this study provide a new approach for examining potential interactions and relationships between land use, fish habitat and fish production. The study contributes a set of baseline data which can be used for future monitoring of fish habitat dynamics in relation to land use changes.

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