Highland Park Dam Mitigation Project Appendix C - Partners for ...

3. Several pages of code were missing from the HEC-2 model hardcopy so assumptions were made to
recreate this section. Missing from the hardcopy were cross-sections S, T, and U (as denoted in the
FIS Swan Creek profile) which were within the Highland Park study area. A copy of the original code
and the recreated code are included in Attachment A. Due to these missing cross-sections, the water
surface elevation (WSE) for the cross-section upstream of the missing code was 0.32 feet higher than
the original model for the 10-year flood event. This makes it difficult to use the recreated model as
the basis for floodplain change comparison.
4. Because of the missing code in the original model, we used existing cross-section data to create the
base model to which we compared proposed changes to the floodplain. Eighteen new cross-sections
through the project area were incorporated into the original model to create the base model. The new
cross-sections were measured in the field in November 2007. A printout of the existing conditions
base code is attached (Attachment B).
Existing Conditions Low Flow Analysis
5. A “low flow” event was simulated to match the water levels observed in the field. The low flow was
confirmed to match the observed flow over the dam. To calibrate the model to observed water levels,
only the Highland Park portion of the model was executed.
Evaluation of Proposed Cross-Sections
6. The proposed cross-sections, representing the rock dams and channel upstream of the dam, were
incorporated into the model. A printout of the code with proposed cross-sections is attached
(Attachment C).
7. With the proposed cross-sections, the low flow event was simulated to predict the water level over the
Highland Park Dam and the rock dams.
8. Shear forces and velocities of the flood events were analyzed using the HEC-2 model so that
appropriate rock size could be determined for construction of the rock dams.
9. With the proposed cross-sections, the 100-year flood event was simulated resulting in no change to
the flood plain as compared to the base model results (existing conditions).
Results
Model Recreation
As discussed previously, by unfortunate coincidence, the cross-sections for the project area were missing
from the hard-copy printout of the original HEC-2 model, which includes the Highland Park Pedestrian
Bridge and the South Bridge. Therefore, the existing conditions model was used as the base model. For
reference, a comparison of the model results are included in Table 1; Figure 1, Figure 2, and Figure 3
show graphical comparisons of the model for the 10-year, 50-year, and 100-year flood events.
10-year flood event = 5,900 cfs (from Lucas County, Ohio FIS, 2000)
50-year flood event = 8,000 cfs (from Lucas County, Ohio FIS, 2000)
100-year flood event = 9,000 cfs (from Lucas County, Ohio FIS, 2000)
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