Hydrology and Hydraulics. Complete a hydrologic and hydraulic analysis of the existing and proposed system. Describe the methodologies used in the analysis and explain the basis of the selected approach.
Hydrology and Hydraulics. FEMA Regulated Crossings
a. In the process of selecting the preferred alternative, the ENGINEER shall gather FEMA regulated floodplain information to be used in comparing impacts on up to three (3) alternatives. No hydrologic or hydraulic modeling will be performed prior to choosing the preferred alternative.
b. The ENGINEER shall coordinate with the floodplain administrator (FPA) of Xxxxxx County and other appropriate jurisdictions to obtain hydrologic and hydraulic information on the FEMA regulated streams that cross this project. The ENGINEER and its staff shall not represent themselves to the FPA as having decision-making authority on behalf of The Mobility Authority. This task includes acquisition of the hydrologic and hydraulic models for the pertinent streams.
c. For Zone AE stream crossings, the ENGINEER shall review the effective hydrological model for recent changes in development and update to a current effective model if necessary.
d. For Zone A stream crossings, the ENGINEER shall create a current effective hydrological model (by using a unit hydrograph methodology such as the NRCS Curve Number Method.)
e. For Zone A and Zone AE stream crossings, the ENGINEER shall create a proposed hydrological model by updating the effective or current hydrologic model to account for the proposed project changes. Proposed project changes could include additional impervious cover, potential sub-basin area changes, potential changes to timing parameters, etc.
1. In those basins along the project where the hydrologic analysis for the proposed conditions determines that the runoff drains into the stream before the main flood peak on the stream arrives, no additional hydrologic analysis of the stream shall be required and the current or effective hydrological model shall be used.
2. In the basins where the proposed hydrologic analysis indicates a potential timing conflict between the main flood peak and the basin specific peak, additional hydraulic analysis shall be performed to determine increases in proposed water surface elevation along the stream. Runoff hydrographs representing the existing and increased impervious area roadway conditions, as well as other relevant project changes shall be used to determine impacts based on timing.
f. For Zone AE stream crossings, the ENGINEER shall review the effective hydraulic model for recent changes in development and update to a current effective model if necessary.
g. For Zone A stream crossings, the ENGINEER shall cr...
Hydrology and Hydraulics. Non-FEMA Regulated Crossings
a. Not including FEMA regulated crossings, the ENGINEER shall model the hydrology of all crossing structures along the preferred alternative.
b. The ENGINEER shall model the hydraulics of all crossing structures using HEC-RAS. The full range of storm frequencies should be evaluated in the analysis, from the 50 percent to the 1 percent annual exceedance probability storm event.
c. Not including FEMA regulated stream crossings, all cross-drain structures (culverts and bridges) shall be identified and evaluated for the preferred alternative only. The following considerations shall be included in the proposed hydraulics analysis and design:
1. Proposed roadway profile and encroachment
2. Degree of upstream and downstream development
3. Proposed alignment/roadway features that could create increases in water surface elevations outside of the State right of way
4. Proposed alignment/roadway features that could create increases in water velocities and erosion impacts. Evaluation of soil types and erosion potential is included here.
5. Impacts and mitigation alternatives.
d. For the preferred alternative, the ENGINEER shall analyze ditches and channels adequately enough to establish proposed project ROW and necessary easements.
e. The ENGINEER shall provide a preliminary cost estimate for all drainage structures for the preferred alternative only.
Hydrology and Hydraulics. Complete a hydrologic and hydraulic analysis of the existing and proposed system. Describe the methodologies used and in the analysis and explain the basis of the selected approach.
a. Hydrology - Develop existing and proposed runoff flows for the 10% (10 year) and 1% (100 year) storm events, at a minimum for each subarea of the watershed for the study area. Provide the appropriate parameters used for the flow calculations, including runoff coefficients, curve numbers (if applicable), time of concentration, percent imperviousness, rainfall intensities and rainfall hyetographs. The project is contained within the Xxxxxxx County Indian Creek Watershed study area, and the 1% (100 year) storm event shall be reviewed for conformance with the SMP requirements.
b. Hydraulics - Develop existing and proposed hydraulic grade lines for the 10% (10 year) and 1% (100 year) storm events, at each structure, enclosed pipeline and open channel.
Hydrology and Hydraulics. Existing hydrologic modeling efforts developed by JEO will be reviewed and utilized to assess performance characteristics of existing conditions and proposed detention cells for up to the 50-year design storm event. New hydraulic models will be developed utilizing HEC-RAS (1D, steady-state) to evaluate proposed channels and culvert crossings.
Hydrology and Hydraulics. No changes or additions to the Scope of Work for this task.
Hydrology and Hydraulics. The GEC shall coordinate with Travis County to develop a drainage design criteria summary for the project. • Drainage Impact Study- The GEC shall prepare a Drainage Impact Study for the Project which includes: o Data Collection o Existing Conditions Hydrologic and Hydraulic Modeling o Proposed Conditions Hydrologic and Hydraulic Modeling o Mitigation Alternatives o Impact Study • Roadway Drainage o Develop External Drainage Area Maps o Prepare Detention Pond Layouts o Prepare Detention Pond Details • Bridge and Culvert Plan Sheets
Hydrology and Hydraulics. The proposed hydrology and hydraulic studies shall be performed in accordance with the Cities of Rancho Cucamonga, Ontario, Montclair, and Pomona, San Xxxxxxxxxx Xxxxx control Design Criteria, US Army Corps of Engineers, and FEMA.
Hydrology and Hydraulics. This task is for the determination of the project’s adequacy in conveying the design storms in accordance with Chapter 11 of the Local Assistance Procedures Manual and Memo to Designers 1-23. For the Xxxxxxxx Creek Bridge Replacement on Xxxxxxx Xxxx Project (Project), WRECO will be responsible for the Preliminary Hydraulic Report and the Final Hydraulic Report. WRECO will attend the kickoff meeting and participate in four (4) conference calls with Mendocino County (County) and the Project Team staff. On a monthly basis, WRECO will provide the Project Team with invoices and progress reports for the Project. WRECO will conduct a field investigation to better understand the related hydraulic design issues.
