(A) Channel routing. Hydrograph channel routing shall be done using the Muskingum-Cunge method using the procedures described in the ADOT Hydrology Manual. Routing reaches shall be subdivided appropriately when the average characteristics of a routing reach cannot be simulated using a single cross section. The number of computation steps for each reach must be optimized so that the number of steps input matches the number of steps calculated using the reach travel time computed by HEC- HMS. The kinematic wave method, or other approved method, may be used for routing hydrographs through storm drains or other prismatic sections where hydrograph attenuation is not expected. Other hydrograph channel routing methods may be used if appropriate for the situation and with prior written approval of the Public Works Department.
(B) Storage routing. All hydrograph storage routing shall be done using the Modified Puls Method as implemented in HEC-1. The operation shall be controlled using an input stage-storage discharge curve. The low-level outlet HEC-1 option shall not be used. The engineer shall document the hydraulic calculations performed to generate the stage-discharge relationship. Hydrograph storage routing shall be performed where hydrograph attenuation is significant due to ponding and storage. This example of hydrograph attenuation could be upstream of a street crossing, through a lake, or for detention basins.
(Res. 1637, passed 2-28-02; Am. Res. 2871, passed 9-17-15; Am. Ord. 872, passed 9-17-15)