Effects of urbanization on sedimentation and floodflows in Colma Creek basin, California

Abstract

This report describes some of the changes in water and sediment discharge that occurred in the Colma Creek basin during a period of major urban expansion. Hydrologic data collected from 1964 to 1971 were used to evaluate trends and relations between sediment yield and land use,, Land use in the basin was estimated from aerial photographs, generally taken annually.The author appreciates the assistance in basic data collection and report preparation provided by George Porterfield and G. 0. Balding. The author is also grateful to V. K. Sanders of the San Mateo County Flood Control District, who provided data from surveys of various debris basins, and L. H. Goss, of the Public Works Department, South San Francisco, for providing historical information on land use changes in the basin. The report received valuable review and criticism from H.

Distribution of seed plants with respect to tide levels and water salinity in the natural tidal marshes of the northern San Francisco Bay Estuary, California

“…Unnaturally large amounts of sediment have been supplied to the San Francisco Bay estuary during the past 125 years because of hydraulic gold mining in the Sierra Nevada (Gilbert, 1917), urbanization (Knott, 1973), and dumping of dredge spoils. Accumulation of sediments derived from these sources may largely account for rapid historic growth of • Native vegetation of the tidal marshes…”

Geologic principles for prudent land use; a decisionmaker's guide for the San Francisco Bay region

“…High rates can be found in areas with heavy rainfall, high relief, a paucity of vegetation, and weak, intensely fractured, or unconsolidated rock or soil, although the relation among these variables is complex and not fully known. Abnormally high rates of erosion may also be caused by urbanization, as was noted for the Colma Creek basin, south of San Francisco (Knott, 1973). Accelerated erosion during urbanization can be attributed chiefly to the removal of vegetation, to extensive grading, and to increased runoff, which also is caused by urbanization.…”

Quantitative land-capability analysis

“…For one erosion province, the bay hills, sediment-yield data exist for four land uses (Knott, 1973). These land uses and yields are given in table 28.…”