Effects of Urbanization On Storm Response in the North Fork San Pedro Creek

Abstract

This study reviews the record of land use change in the San Pedro Creek watershed, in Pacifica California, focusing on the effects of 50 years of urbanization. Storm related discharge and turbidity were measured and compared for the undeveloped Middle Fork and partly developed North Fork tributaries to quantify differences associated with impervious surfaces and increased drainage density from hillside residential development. Continuous recording data loggers in both tributaries measured rainfall, turbidity, and stage (used to estimate discharge) during three storm events. Rainfall values were consistently higher in the Middle Fork drainage but response time of discharge in the North Fork was faster and resulted in peaks of greater magnitude and frequency. Middle Fork turbidity was, on average, 10 times greater than the North Fork. Bank erosion, measured downstream of the Middle and North Fork confluence, was the greatest per linear foot when compared to the rest of the San Pedro Creek main stem.