From here, the Waiau continues south across a relatively narrow plain, fed by numerous small creeks and burns, the largest of which are the Excelsior, Whare and Redcliff Creeks and the Borland Burn. At Monowai it is met by the Monowai River, the outflow of a further glacially formed lake, also named Monowai. At the Waiau's junction with the small Wairaki River the plain widens. From here the Waiau is fed by numerous other streams and burns, notably the Lill Burn close to Clifden and the Alton Burn, as well as the Orauea River, close to Tuatapere. As the river nears the coast it widens, with several small low-lying islands contained within its channels At its mouth on Te Waewae Bay, the river forms a long tidal lagoon separated from the sea by a narrow sandbar which extends along the coast for several kilometres.