Channel Cross-Section Analysis in Alhambra Creek

California, has changed over the past 50 years in some areas from cropland and rangeland to residential subdivisions and urban development. The effects of urbanization on watershed hydrology and stream geomorphology have been extensively explored. Streams in urban watersheds tend to increase in cross-sectional area, as changes in runoff-generating mechanisms result in larger peak flows than in non-urban watersheds. These geomorphic changes can have serious detrimental effects on both the quality of aquatic habitat and the stability of infrastructure and bridges. This study investigates historical channel changes in Alhambra Creek, focusing on the question of whether or not channel incision and expansion has occurred due to hydrologic changes since the 1950s. To answer this question, I resurveyed ten channel cross-sections and compared them to 1955, 1962, and 1971 cross-sections. I found that minor channel changes have occurred, including both local channel expansion and contraction. Due to the prevalence of bank revetment in my study reaches, it is difficult to determine if the observed changes in the past 30 to 50 years are a result of changes in hydrologic processes, recent and past efforts to stabilize the channel, or a combination of these factors. Surveying limitations and small sample size also affected the statistical strength of my results. Based on my understanding of the available current and historical cross-section data, I conclude that the Alhambra Creek channel morphology is generally stable, excluding local erosion problems exacerbated by in-stream structures