IMPACTS OF RAINFALL DATA COLLECTION TECHNOLOGIES ON SANITARY SEWER CAPACITY ASSESSMENT

Rainfall is monitored concurrently with monitoring the flow in the sewer system to establish the relationship between wet weather flows and rainfall. Since rainfall patterns vary both geographically and temporally, a rainfall monitoring program that accurately measures these variations is important to understanding system flow response to rainfall. Accurate rainfall data are used in developing design storm flows crucial to accurate capacity assessments, a component of Capacity, Management, Operations, and Maintenance (CMOM).Temporal and spatial resolution criteria for rainfall monitoring are recommended when collecting rainfall data suitable for infiltration/inflow assessment. A temporal resolution of 15 minutes should be used for rainfall data collection. Fifteen-minute data retrieval provides satisfactory temporal resolution when considering fast moving storms and the corresponding flow monitoring data collection plan. The spatial resolution should be of sufficient accuracy to measure variations in rainfall for correlation with flows monitored for each subsystem. While rainfall data with an acceptable temporal resolution rarely is a problem, this paper focuses on the monitoring technologies that impact the spatial aspect of rainfall data collection.The two rainfall monitoring methods considered are traditional ground based rainfall monitoring, advanced remote sensing rainfall monitoring, and the combination of these technologies.For this paper, a comparison of rainfall totals for various events and projected 5-year inflow rates was conducted using rainfall data measured by two different methods.