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