Consultant Services

The vendor is required to provide consultants to update the county hydrology manual.
1. Rainfall and stream gauge data assessment and analysis
a. Once the rainfall and stream gauge database has been reviewed and compiled, if the data is found to be unusable, provide recommendations on the following:
• Format of the data for future calibration efforts or other county needs
• How the county can QA/QC future data
• If there are any adjustments to the overall network that should be made
• If there are data gaps in the network
• where future rainfall/stream gauges (including type of gauge) could be installed that would be the Most beneficial for future calibration efforts.
b. If administration atlas 14 is not recommended for adoption, establish the 2-, 5-, 10-, 25-, 50-, 100-, 200-, 500- and 1000-year return frequency rainfall for the 5-min, 10-min, 15-min, 30-min, 1-hour, 2-hour, 3-hour, 6-hour, 12-hour, and 24-hour durations for the 85% and 50% confidence levels.
c. If spatially varying rainfall is proposed, develop is hiatal maps for the county in pdf, cad, and GIS format at industry typical contour increments to be included in the updated agency.
2. Calibration of the agency/hydrologic modeling
• Re-analyze the agency flood frequency curves by extending the 2007 report titled “evaluation of the need to update and/or recalibrate the county hydrology manual” by Hromadka & associates to the most recent available data.
• Results and conclusion for the 85% and 50% confidence levels to be included in the final calibration report to support the agency update.
• Develop a calibration plan in consultation with organization, using the watersheds (both developed and undeveloped) unique to county and measured rainfall from phase 2, in order to establish a methodology (either confirmation of the adequacy of the current methodology or proposal of a new methodology) and reasonable confidence intervals for determining a rainfall to runoff relationship.
• Hydrologic parameters (i.e., time of concentration, DARF (depth-area reduction factors) or design storm depth area curves, curve number, land use, soil type, loss rates, s-graph, time of concentration, AMC (antecedent moisture condition) etc.
3. Post-fire watershed hydrology
• Research available methodologies on calculating post-fire watershed discharges (which would include debris and bulk).
• Include descriptions of assumptions and procedures used by various agencies in the region.
• Provide recommendation to adopt an existing methodology, or if an existing methodology is not compatible to the procedures in the agency update, provide a step-by-step procedure for estimating the watershed response (bulked flow) to rainfall after a fire (post-fire watershed hydrology). hydrologic inputs that could be different than a standard hydrology analysis (i.e., change in land use, soil type, AMC value, etc.) should be noted.
• Procedure and results will be documented in the final calibration report, and added to the updated hydrology manual.
4. Climate change and the agency
• Research the various ways other agencies have accounted for climate change in their hydrology manuals, as well as the current state of climate models, the occurrence of extreme weather events, forecasts from relevant government and research entities, and current data models and trends.
• Provide a short write-up that will be added to the final calibration report and the updated hydrology manual.
5. Hydrology software
• Agency is open to utilizing other software that may offer more robust modeling options, specifically HEC-HMS.
• Research available software that is compatible with the hydrologic parameters in the agency and provide a summary of the various software and capabilities.
• If it is recommended to utilize HEC-HMS, develop a step-by-step procedure on how to perform hydrology calculations and added to the updated hydrology manual.
- Contract Period/Term: 1 year
- Questions/Inquires Deadline: June 03, 2025