ABSTRACT
This chapter presents a case study on the improvement of an existing culvert using a tapered inlet. The effectiveness of the improved system was evaluated by hydraulic modeling. Old drainage systems are usually upgraded by enlargement of the culverts or addition of parallel lines. The drainage capacity of the brick culvert under the railway line was found to be inadequate when severe flooding occurred in April 1988. The flow from the 1500-mm pipe bent sharply at right angle to the railway line culvert while the flow in the creek curved around at an angle of 37°. The two inflows then merged and formed a pondage near the entrance to the brick culvert. Models of the brick culvert, concrete pipe, the transition and the tapered inlet were built with perspex. Catchment analysis indicated that the proportions of flows through the creek and pipe culvert were approximately 45% and 55% of the total flow through the railway line culvert.
