Figure legends

Figure 1. Captured images of root intrusion in sewer pipes through (a) pipe cracks, and (b) pipe joints (Urbana Champaign Sanitary District, 2012)
Figure 2. Rainfall and sewer flow data: (a) rainfall record from ISWS, and (b) sewer flow data from USGS sewage monitoring site in the period of April 17–August 3, 2009
Figure 3. Impulse response functions from the roof connection, sump pump, and leaky lateral models as flow discharge per unit contributing area (Black solid line indicates the roof IRF, black dashed line indicates the sump pump IRF, and the grey solid line indicates the leaky lateral IRF.)
Figure 4. Exceedance probability of three RDII responses per unit area in log scales in the period of April 17–July 16, 2009
Figure 5. Three RTK triangular hydrographs from 30 different model runs that show inconsistency of the solutions: (a) “fast” hydrograph, (b) “medium” hydrograph, and (c) “slow” hydrograph
Figure 6. Box plots of RTK solutions that indicate interdependency of the nine parameters: R1, R2, R3, T1, T2, T3, K1, K2, and K3 (R: ratio of I&I discharge volume to the rainfall volume, T: time to peak in each hydrograph, K: ratio of time of recession to the time to peak, 1: fast inflow element, 2: medium infiltration element, and 3: slow infiltration element)
Figure 7. Calibrated IRF and the best RTK results in the (a) calibration period (May 9–June 7, 2009) and the (b) validation period (June 9–July 8, 2009)
Figure 8. Residual plots of IRF (depicted with light grey diamonds) and RTK methods (depicted with dark grey squares) for (a) calibration period and (b) validation period