North of San Fernando, the San Gabriel Mountains crest abruptly up to almost . Pacoima and Big Tujunga Canyons cut through the range just east of San Fernando, carrying runoff into the San Fernando Valley. Little Tujunga Canyon Road bridges the range in this area, connecting the San Fernando Valley to the Santa Clara River valley in the north. Towering over Big Tujunga Canyon north of Big Tujunga Reservoir is Mount Gleason, which at , is the highest in this region of the San Gabriels. South of the gorge are the southern foothills of the mountains, which rise abruptly above the Los Angeles Basin and give rise to the Arroyo Seco, a tributary of the Los Angeles River.