Nonlinear Extrapolation of Inflow and Infiltration Behavior under Heavy Storms

Abstract

A two-sample nonlinear heteroscedastic regression model is described and proposed for the purpose of evaluating a sewer basin rehabilitation by quantifying the reduction in rain-derived inflow and infiltration (RDII). The proposed methodology is used at the second stage of RDII studies after RDII volumes of individual rain events are estimated. The proposed methodology utilizes boundary conditions of system capacity and extrapolates the RDII behavior under usually unobserved heavy design storms in short-term flow data series—a common problem in RDII studies. As compared to the commonly used linear models, the proposed methodology offers flexibility in modeling, reasonable extrapolation, and simplicity in interpretation.