Improve the flow rate will not change by HEC RAS at Austin (only USA!!)
Budget: $250 – $750 USD
"Can someone revise the county's comment regarding the fish pond and ensure that after development, the flow rate during a 100-year flood will not affect the river, as assessed by HEC-RAS?
6. This project appears to be located within a FEMA floodplain on the San Bernard River. Please
provide a floodplain impact analysis using the San Bernard River FEMA model. Any fill in the
floodplain must be mitigated so as to ensure no rise in the 100-yr floodplain.
Goldand Reply – The calculation is indicating the peak flow of the pre-development at
100-year event is 7.62 cfs. The proposed development provides adequate detention pond
to store the water runoff from the increase impervious cover and the whole site of the
deployment area. The detention pond is included the fill volume of the dike below the
100 BFE 71.30. The detention pond has the 6” restrictor outfall. It is only discharge 0.99
cfs to the existing side road ditch. Comparing the existing discharge of 7.62 cfs and the
proposed discharge 0.99 cfs. It is significantly different, and it is a lot lower flow than the
existing. This is clear evidence of no increase in the 100-year flood plain. So, there is no
impact to the flood plain of the San Bernard River.
The plans are not clear on where the proposed detention pond is to be located. Is it the area
around the circular pond? Please identify the proposed detention pond, provide a cross-section
for this pond, provide 2-, 10-, and 100-yr HGL profiles in the cross-section, provide details for the
outlet structure (if different from the pump station), and location of the outlet structure. Please
also provide computations for sizing the outlet structure to ensure no increase in runoff for the
2-, 10-, and 100-yr Atlas 14 flood events.
Goldand Reply – It is corrected on the update grading plan. The cross section is revised.
The design change from 3 ft deep detention to 1 ft deep shallow detention pond. The out
fall is a 12 in RCP with 6 in restrictor. It is very shallow outlet structure.
Scheibe Comment – Please include the HGL profiles in the cross-sectional profiles shown on
Sheet C-105.
Scheibe Comment: An impact analysis is not just the impact due to increased runoff, but also
the impact due to fill in the floodplain. The only way to evaluate impacts due to fill in the
floodplain is to simulate the fill and non-fill condition in the FEMA RAS model and verify no
change in peak water surface elevation for the 100-yr flood. Please perform the requested
floodplain study.
I am looking for an experienced professional with expertise in using the HEC-RAS to improve existing flow rate at Austin. The river and bank conditions in Austin are newly developed, so this project requires careful analysis of data and simulations for determining the changes that need to be made. The analysis will focus on flow rate, so the contractor should have experience working with relevant data sets, performing simulations and interpreting results. The contractor should be prepared to integrate the results with specified design criteria, identify deficiencies and generate solutions that are compliant with the design standards. Since this is a complex undertaking, the contractor must also provide detailed written reports that document the entire process. The evaluation of the solutions provided must also meet alternate engineering analysis approaches. If you have the necessary technical expertise and experience to take on this task efficiently and effectively, please get in touch soon.
6. This project appears to be located within a FEMA floodplain on the San Bernard River. Please
provide a floodplain impact analysis using the San Bernard River FEMA model. Any fill in the
floodplain must be mitigated so as to ensure no rise in the 100-yr floodplain.
Goldand Reply – The calculation is indicating the peak flow of the pre-development at
100-year event is 7.62 cfs. The proposed development provides adequate detention pond
to store the water runoff from the increase impervious cover and the whole site of the
deployment area. The detention pond is included the fill volume of the dike below the
100 BFE 71.30. The detention pond has the 6” restrictor outfall. It is only discharge 0.99
cfs to the existing side road ditch. Comparing the existing discharge of 7.62 cfs and the
proposed discharge 0.99 cfs. It is significantly different, and it is a lot lower flow than the
existing. This is clear evidence of no increase in the 100-year flood plain. So, there is no
impact to the flood plain of the San Bernard River.
The plans are not clear on where the proposed detention pond is to be located. Is it the area
around the circular pond? Please identify the proposed detention pond, provide a cross-section
for this pond, provide 2-, 10-, and 100-yr HGL profiles in the cross-section, provide details for the
outlet structure (if different from the pump station), and location of the outlet structure. Please
also provide computations for sizing the outlet structure to ensure no increase in runoff for the
2-, 10-, and 100-yr Atlas 14 flood events.
Goldand Reply – It is corrected on the update grading plan. The cross section is revised.
The design change from 3 ft deep detention to 1 ft deep shallow detention pond. The out
fall is a 12 in RCP with 6 in restrictor. It is very shallow outlet structure.
Scheibe Comment – Please include the HGL profiles in the cross-sectional profiles shown on
Sheet C-105.
Scheibe Comment: An impact analysis is not just the impact due to increased runoff, but also
the impact due to fill in the floodplain. The only way to evaluate impacts due to fill in the
floodplain is to simulate the fill and non-fill condition in the FEMA RAS model and verify no
change in peak water surface elevation for the 100-yr flood. Please perform the requested
floodplain study.
I am looking for an experienced professional with expertise in using the HEC-RAS to improve existing flow rate at Austin. The river and bank conditions in Austin are newly developed, so this project requires careful analysis of data and simulations for determining the changes that need to be made. The analysis will focus on flow rate, so the contractor should have experience working with relevant data sets, performing simulations and interpreting results. The contractor should be prepared to integrate the results with specified design criteria, identify deficiencies and generate solutions that are compliant with the design standards. Since this is a complex undertaking, the contractor must also provide detailed written reports that document the entire process. The evaluation of the solutions provided must also meet alternate engineering analysis approaches. If you have the necessary technical expertise and experience to take on this task efficiently and effectively, please get in touch soon.