Final Engineering services report _62 Lake Macdonald Drive · OPW25/0057

                                                                                        Flood Hazard Assessment
                                                               Intersection of Lake Macdonald Dr and Dianella Crt



6        SENSITIVITY ANALYSIS
To test the sensitivity of the high-resolution local flood model to modest changes in adopted
parameter values, two sensitivity tests were conducted. A reference point (A) was adopted at the
road entrance to Dianella Crt where hydrographs were extracted from the flood model and
compared to the base case results. See Map 3 for reference point location.

6.1 Manning’s n roughness sensitivity
The first sensitivity test was conducted using a +/- 25% variation in the adopted Manning’s n surface
roughness value for the model. The adopted Manning’s n surface roughness values are shown in
Table 4-1.

Water level (Depth) hydrographs were extracted from the results of each sensitivity analysis at
reference point A and compared to the base case results for the 2% AEP, 1% AEP, and 0.2% AEP
design flood events. See Figure 10 to Figure 12.

The results show the design flood levels at the intersection are not sensitive to reasonable changes
in the adopted Manning’s n surface roughness.




Figure 10 - Sensitivity analysis +/- 25% Manning's n 2% AEP at Reference Pt A




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