5.2.4 STORM SUBCATCHMENT DELINEATION
The storm subcatchment delineation account for physical topography of the overland system, along with the influence of drainage features such as curbs, lot-grading and depressed parking lots. Preliminary subcatchments are delineated using automate tools which utilizes the DEM. The subcatchments are then manual reviewed to ensure accuracy and that the all residential roofs and front lots drain to the street in front. The subcatchment extents three (3) meter beyond the perimeter of the building layer.
The assignment of roofs is also completed using an automated “Spider Tool” which assigns the roof to the appropriate system in front of the property. The assignment of roofs follows the rules …show more content…
The blank subcatchment is will not be used for calibration of the model as part of this assignment. The City may choose to use this blank subcatchment in the future to further investigate the inflow and infiltration to the system, and/or to identify the impacts of the foundation drains as a separate flow contribution within the model.
5.2.5 FLOW ASSIGNMENTS
This section outlines how flows should be assigned from subcatchment sources to the sewer network in combined sewer areas. There are three (3) general street/sewer configurations in combined sewer areas that require separate approaches to flow assignments. In order to ensure that the areas contributing to the sanitary, combined, and storm sewers do not overlap, the following flow assignments must be applied in the scenarios listed below. In applying this approach, all areas will contribute to the sewer system only …show more content…
6 SUMMARY OF ASSESSMENT
The following conclusions can be drawn from the information supporting this report:
Based on available flooding records, there is no apparent flood cluster area(s). The model results will be used to determine location in the drainage network that are at risk of flooding if a significant event was to hit the study area.
Data gaps from field investigations and data collection do not significantly impact the model development. Flow monitoring data and additional field visits by the modeling staff will be used, where required, to validate the model performance.
Given the rainfall variation across the study area, model calibration will be carefully considered. If challenges arise during calibration, additional measure to supplement rainfall data will be considered with the City’s staff.
Although I/I measured in the sanitary catchment is above the City design standard of 0.26L/s/ha for a projected 25-yr storm event, the values are not considered to be a “chronic”