the city of San Bruno modified greatly the upper and lower reaches of the watercourse. Above the intersection of Interstate 280 and Interstate 380, the creek runs through Crestmoor Canyon and the Crestmoor residential neighborhood, which was the site of the 2010 San Bruno gas pipeline explosion and fire. Upper reach The upper of San Bruno Creek is the most rugged and natural reach as the stream winds through steep canyons of about 45 degrees in slope. The underlying geological formation of this upper catchment basin is Pleistocene Colma Formation, which continues eastward in the basin under most of the San Francisco Bay Flood Plain. Principal flows of the creek are within the winter months of November to March, the only season of meaningful rainfall in the Bay Area. Groundwater in the middle to upper basin varies between about , and flows generally eastward toward the Bay. This wooded upper reach watershed consists of a mixed oak woodland with coast live oak, Quercus agrifolia, as a dominant species. Other larger plants are the California Bay Laurel and the understory species Toyon. The understory also includes the following wildflowers: evening primrose (Renothera ovata), wild radish (Raphanus satira), wild cucumber (Marah fabaceus), scotch broom (Cytisus scoparius), miners lettuce (Montia perfoliata), fillaree (Erodium cicutarium), vetch (Vicia americana), sweet clover (Melilotus indicus), lupine (Lupinus sp.), and California poppy (Eschscholzia californica). See also Colma Creek The Shops at Tanforan List of watercourses in the San Francisco Bay Area References Rivers of San Mateo County, California San Bruno, California Rivers of Northern California