Complex sentence: The Tolka has many tributaries, starting with the Castle Stream at Dunboyne, and with at least fourteen infalls within Dublin City boundaries (the count is complicated by connections with the Wad River system).
Split into simpler sentences: The Tolka has many tributaries, the first major one being the Castle Stream at Dunboyne. There are at least fourteen infalls within Dublin City boundaries (the count is complicated by connections with the Wad River system).