Flow modeling
View sample flow modeling maps (maximum calculated 20-year peak infiltration and inflow hourly flow rates in the King County system).
King County and the local agencies use flow monitoring data and other data to model existing flows and to project future flows in the system. The purpose of the modeling is to determine the condition of the regional conveyance system and to measure its long-term capacity to convey existing and projected wastewater flows. The County uses a hydraulic modeling software—MOUSE™ (Modeling of Urban Sewers)—a PC-based computer model with a graphic interface to GIS. To ensure that modeled flow projections are accurate, the model is calibrated by comparing model results to measured data. Both the hydrologic and hydraulic components of the model are calibrated to base flow and I/I data collected. Other inputs to the calibration include a 60-year rainfall record and basin-specific pipe and service area information. The calibrated basin models are then used to simulate I/I flows that could occur in the regional system over a 60-year period. The results of this 60-year simulation are used to estimate the 20-year peak flow in gpad for each model basin. The estimated peak flow serves as an indicator for the performance of each local agency system. Definitions of modeling terms Hydrologic model: A model used to numerically simulate the physical process of rainfall becoming I/I. Hydraulic model: A model of the actual pipes that convey the wastewater and I/I generated by the hydrologic model. The hydraulic model outputs flow depths and velocities in specific pipe segments and allows for the evaluation of system performance under existing and future demands. Basin: A geographic area that contributes flow to a specific location, usually a flow meter or a facility. The two primary types of basins used in the assessment are model basins and mini basins. Model calibration: The process of adjusting model parameters so that the model output matches the measured sewer flow for the same time period. |
