Armstrong & Brooks Consulting Engineers, Inc.

Water Resources and Hydraulics

Armstrong & Brooks performs water resource design services on most of their projects.  Typical services vary, and are described below:

Drainage Research and Review

A&B performs research and reviews existing hydrology and hydraulic documentation related to existing and proposed storm drain improvements within a project’s limits. The available documentation and topographic maps are used to identify drainage constraints and deficiencies.

Hydrology Analyses

A&B performs a hydrology analyses to evaluate the runoff tributary to a proposed project. The purpose of the study is to determine flow rates that will be used to establish storm drain alignments in order to flood protect a proposed project against the 10-year and 100-year storm events as required by the CITY or RCFC&WCD.  The hydrology analyses will dictate the location of the proposed catch basins and storm drain systems for the proposed improvements. The following tasks will be performed as part of the hydrology analysis:

  • Utilize the Riverside County Flood Control and Water Conservation District Hydrology Manual and the Rational Method to evaluate the 10-year and 100-year flow rates using the CIVILD Hydrology Program for the existing condition.
  • Utilize the Riverside County Flood Control and Water Conservation District Hydrology Manual and the Rational Method to evaluate the 10-year and 100-year flow rates using the CIVILD Hydrology Program for the most current CITY General Plan.
  • Prepare a hydrology map that delineates the watershed boundary, nodal points, flow patterns for the watershed area the existing condition and ultimate condition.
  • Evaluate the street capacity using the FlowMaster Program which incorporates the Manning’s equation.
  • Prepare a field reconnaissance based on field review of hydrology boundaries.
  • Perform hydrology calculations using the Riverside County BMP Handbook to determine flow rates and volumes required to treat the runoff associated with the treatment of water quality low flows.

Conceptual Storm Drain and BMP Improvement Plans

A&B will prepare a conceptual storm drain improvement plan together with a Best Management Practice analysis to identify BMP’s capable of treating constituents listed for the 303d water bodies downstream of a proposed project. The plans will be prepared using standards and criteria established by RCFC & WCD and CITY.  Additionally, the improvement preliminary plan and profiles will include inlet and outlet structures required to collect and discharge the runoff tributary to a project. The preliminary plan and profiles will consist of the following:

  • Preliminary alignments, cost estimates, and hydraulic analyses evaluating the feasibility of alternatives.
  • A matrix evaluating each alternative in order to establish a preferred alternative plan.
  • Catch basins location and design analysis based on flooding criteria and sump locations.
  • Treatment BMP analysis and prelim. design using the County’s BMP Handbook and design criteria.
  • Prelim. hydraulic analysis for all inlets, outlets and storm drain anticipated for a project.

Flood Plain Analysis

If needed, A&B will perform a hydraulic model using the HEC-RAS computer program. The model will be based on sections using the RCFC & WCD topographic maps and previous models obtained from RCFC & WCD or other studies. The study will evaluate the maximum encroachment of fill into the flood plain that does not impact the downstream and upstream properties. The analysis will include the following:

  • A HEC-RAS model for the pre-project condition to assess the current flood plain and flood way limits in order to establish the existing flood plain and floodway baseline condition.
  • A HEC-RAS model for the post-project condition to assess the flood plain and flood way limits that have been changed as a result of fill material encroaching into the drainage course
  • Preparation of pre-project and post-project flood plain maps for drainage course to establish the limits of fill material and right-of-way for RCFC & WCD.
  • Determination of scour depth anticipated for the proposed slope armorment that may be required for a project site.

Hydrology and Hydraulic Study

A&B will prepare a report that documents the preliminary hydrology and hydraulic analyses performed for a proposed project. The report will substantiate the results of the hydrology and hydraulics required for the design alternatives. The report will provide the preferred alternative that meets parameters associated with cost, environmental permitting, utility conflicts, right-of-way and easement conflicts, and flood protection. The hydrology and hydraulic study will consist of the following:

  • A technical narrative that provides the hydrology and hydraulic parameters utilized in the project. The narrative will include a discussion on hydrology, hydraulic, and the flood plain results associated with the design.
  • Catch basin analysis using the FlowMaster Program which incorporates design analysis established by the Federal Highway Administration.
  • Street capacity calculations using the FlowMaster Program which incorporates the Manning’s equation.
  • Hydraulic analysis using the Water Surface Pressure Gradient Program (WSPG) developed by Los Angeles County Flood Control District. The project will utilize the WSPG program that is distributed by CivilDesign Software.
  • Excerpts and back-up documentation related to existing storm drain systems that impact the proposed storm drain systems.
  • Preliminary design of the proposed BMPs required for the project improvements.

Preliminary Water Quality Management Plan

A&B will prepare a preliminary WQMP that will be used to document the design and water quality requirements for a project. A preliminary WQMP is typically required as part of the Regional Water Quality Board environmental permitting process. The following will be performed as part of the preliminary WQMP:

  • Evaluate the constituents of concern related to each land use.
  • Provide a matrix that identifies potential BMPs that treat the constituents of concern identified for the downstream water courses.
  • Perform water quality hydrology analyses to size the potential BMPs using the guidelines established in RCFC & WCD BMP Handbook.