FALL BRANCH. Fall Branch rises a mile north of Interstate Highway 10 in the hills of the eastern Edwards Plateau in southwestern Gillespie County (at 30°12' N, 99°16' W) and runs south for about seven miles to its mouth on Johnson Creek, in north central Kerr County (at 30°07' N, 99°17' W). The stream, which is intermittent in its upper reaches, traverses flat terrain surfaced by shallow loamy and clayey soils that support grasses and open stands of live oak and Ashe juniper.