Complex sentence: It flows roughly north for about to meet the Big Lebanon and with it form the South Branch of Big Timber Creek, which runs north for about to the point where it joins the North Branch just upstream from Clement's Bridge in Glendora.
Split into simpler sentences: It flows roughly north for about to meet the Big Lebanon and with it form the South Branch of Big Timber Creek. The South Branch proper runs north for about to the point where it joins the North Branch just upstream from Clement's Bridge in Glendora.