Engineering Disciplines


Hydrology and Hydraulic Modeling & Assessment

Hydrologic & Hydraulic Feasibility Study, Phase II, Bel Marin Keys, CA.

NCI is currently under contract with the Corps of Engineers (San Francisco District) to perform on-call design services for navigation and water resources projects. The Phase II study for the Bel Marin Keys V Wetland Restoration project is part of the overall Hamilton Wetlands Restoration and the work order is to perform an assessment of hydraulics, hydrodynamics, and sediment movement in Novato Creek located in San Francisco Bay. The tasks include bathymetric survey in Novato Creek, deployment and retrieval of tide gages and current meters, and hydraulic & hydrodynamic numerical simulations. The hydraulic simulations are to assess the potential impacts to water levels at various reaches of the creek under 19 different scenarios of flood and project improvement conditions. The tidal-induced estuarine hydrodynamic modeling is to characterize water level and currents throughout the Lower Novato Creek so as to address any potential shoaling and scouring impacts resulting from the proposed Bel Marin Keys V wetland restoration.


San Joaquin Marsh Enhancement, Phases I and II, Irvine, CA.

San Joaquin Marsh is a fresh water marsh that is managed as part of the University of California Natural Reserve System. The purpose of the Phase I Enhancement was to provide a reliable water source to a series of managed ponds to promote native marsh habitat. Noble Consultants was responsible for the planning; permitting; investigation; surveying; design; cost estimation; and preparation of plans, specifications, and contract documents for improving approximately 40 acres of historic wetland. Design services included civil, electrical and mechanical engineering, and landscape architecture. Construction oversight was also provided. The California State Coastal Conservancy funded this work. The project components included removing invasive plant species; grading twelve ponds to provide a setting for a range of native plant species; improving existing internal levees; constructing a pump station and a pipeline system to provide water to all of the ponds; installing water control structures; and planting native species.

Phase 2 of the San Joaquin Marsh Enhancement Project involved recreating the historic hydrology of the marsh by improving the infrastructure for routing and delivering water throughout the area adjacent to the managed ponds that were enhanced in Phase I. Noble Consultants was the prime consultant responsible for the project, under contract with the University of California, Irvine for Phase II while for Phase I work Noble Consultants was under contract to the California State Coastal Conservancy. Work for this phase involved surveying, planning, permitting, design, and preparation of contract documents. The design services included civil, electrical, and mechanical engineering, and wetlands design. Project components included excavation to provide channelization for water distribution; excavation to create a muted fresh water marsh connection to the creek; construction of a pipeline through a flood control levee; construction of a pipeline from an existing well to supplement creek water; and improving existing levees.


Laguna Niguel Lake Refurbishment, Laguna Niguel, CA.

NCI provided the engineering services for removing 200,000 cubic yards of accumulated material from a 40-acre lake and constructing miscellaneous lake improvements. Engineering services included planning; permit preparation and processing; sampling and testing; design; preparation of plans, specifications and cost estimates; quantity computations; alternative disposal site analysis; and construction services. Due to budgeting constraints, the project was to be phased over a five-year period. As a result of planning, the optimum project involved draining the lake; removing 100,000 cubic yards of material by processing it and reusing it to create an in-lake, 4-acre dredged material disposal site, to improve lake perimeter roads, and to reconstruct a wildlife island; landscaping; and, aquatic vegetation planting to improve water quality. The engineering included design of the disposal area perimeter dike and decant weir, and specifications for future dredging of the remaining material with placement in the disposal area. Additional funding became available during construction that allowed removal of all accumulated material. Excess material was placed in the disposal area. Subsequently, NCI prepared plans and specifications for removing the stockpile and disposal site perimeter dike material, and using it on a County road project.

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Hansen Dam 15-Acre Recreational Lake, Los Angeles, CA.

The Corps of Engineers was directed to plan, design and construct a recreational lake and associated recreational facilities at Hansen Dam. To initiate the planning and design process, NCI prepared the Feature Design Memorandum that presented all engineering design criteria for final design and construction of a 2-acre swimming area for swimming, sunbathing and child's wading activities; a 13-acre recreational water area for non-powered boating, sailing and fishing uses; and associated recreational facilities for parking, turf/picnic areas, restrooms, lifeguard buildings and stands, launching ramp, footpath and service road. This included engineering criteria for all civil design, hydraulic design, landscape design, and design of associated recreational facilities. Design elements consisted of the lake's physical layout; lake liner and shoreline treatments; drainage features; and water quality control for the swimming area, filtration pond and recreational area. Water quality control consisted of chlorination, circulation/filtration, aeration and ozonation systems. A comprehensive construction cost estimate and operations/maintenance cost estimates were developed for this project using the Corps' M-CACES program.


South Bay Salt Pond Restoration-Pond A8 Bridge & Weir Design, Alviso, CA.

The Pond A8 bridge and weir are an integral part of a restoration project to provide tidal flow between an historic salt pond and Alviso Slough.  The bridge is required to maintain access around the levee system after the channel through the levee is excavated.  The weir is required to control tidal exchange to obtain the design hydraulic conditions.

NCI was responsible for performing the detailed structural design and calculations, preparing construction drawings and special provisions, and preparing the Engineer’s construction cost estimate for these project components.  The structure consists of precast-prestressed concrete foundation piles and double Tee deck joists, cast-in-place concrete caps, floor, walls, deck and stop log columns, and an 8 bay adjustable stop log weir system.


San Francisquito Creek Hydraulic Study, San Francisco, CA. 

NCI was retained by the Corps of Engineers (San Francisco District) to develop a one-dimensional steady HEC-RAS model of San Francisquito Creek for the purpose of evaluating the flow capacities of the existing channel and the major bridges on the creek.  The modeled reach is from the mouth of the creek to approximately one mile upstream of Highway 280, with a total length of approximately 55,000 feet. 

A Digital Terrain Model (DTM) was constructed using the channel topographic survey data and the LiDAR data for the project area.  The geometric data of the hydraulic model was developed using HEC-GeoRAS based on the DTM.  More than twenty bridges were incorporated in the model.  After calibrating and verifying the HEC-RAS model using three historic flood events, the model was used to simulate four other historic flood events that caused flooding of the creek.  The existing flow capacities of the creek and bridges were evaluated based on the model simulations for a series of flow discharges.  A sensitivity analysis was conducted to test how the Manning’s roughness coefficient impacts the predicted flow capacities.  This hydraulic model can be used to assess future flood conditions, delineate floodplains, and assist in the development of alternatives for the San Francisquito Creek flood damage reduction and ecosystem restoration projects.





San Francisquito Creek, Hydraulic Modeling and Floodplain Mapping, San Francisco, CA.  

The purpose of this study was to produce and/or update the existing floodplain mapping along the San Francisquito Creek from HWY 280 to the San Francisco Bay.  An unsteady HEC-RAS model was developed based on the steady model.  By applying the flow hydrographs and representing the potential flow breakout locations as lateral structures, this unsteady model was able to predict the flow breakout from the creek during the extreme flood events and would predict the flood conditions along the creek more realistically and more accurately. 



The unsteady HEC-RAS model was re-calibrated using three historical flood events.  After the coincident frequency analysis (CFA) was performed by the Corps, this model was further revised, with the downstream boundary condition being updated with the water stages determined in the CFA for the index station.  The flow condition for the San Francisquito Creek was predicted with the revised unsteady model for eight flood events with the return periods of 2, 5, 10, 25, 50, 100, 250, and 500 years.  The breakout flow hydrographs at all the breakout locations along the creek were determined based on the model results, and were input into the FLO-2D model as inflow hydrographs.  The floodplain modeling was then conducted using the FLO-2D model, and the floodplain maps were generated in ArcMap.


Guadalupe River Risk & Uncertainty Analysis, Santa Clara County, CA. 

The purpose of this risk and uncertainty analysis is to evaluate the project performance for the implemented Lower and Downtown Guadalupe River Project and for the proposed Upper Guadalupe River Project.  The HEC-RAS and HEC-FDA models were used in this analysis.  Both the existing conditions with the Lower and Downtown Guadalupe River Project, and the proposed Upper Guadalupe River Project design plans were investigated.

The three bypass projects in the downtown area of San Jose were incorporated into the existing HEC-RAS models for Guadalupe River.  The new models were calibrated using the data from the physical models.  The normal (50% probability) water surface profiles along the river were predicted using the new HEC-RAS models.  The variation ranges of the water stages were computed by adjusting the model parameters, from which the standard deviations of the stage-discharge uncertainties were determined.  Using the computed stage-discharge relation with the standard deviation of error and the discharge probability function with the statistical uncertainty, the HEC-FDA model was used to compute the conditional non-exceedance probabilities for the 100-year flood event.  The project performances for the implemented projects and for the proposed project alternatives were evaluated based on the freeboard requirements for the 90% or 95% probability of non-exceedance in the 100-year flood event for the floodwalls, levees and incised channels, respectively.




Hurricane Katrina Flooding Evaluation, New Orleans, LA.

NCI was contracted by WTHF to review the Interagency Performance Evaluation Team (IPET) reports that were prepared by several independent investigation teams to understand “what happened” in the New Orleans areas during Hurricane Katrina.  After a site inspection and a comprehensive report review, NCI was further requested to perform hydraulic & hydrodynamic numerical modeling analyses in order to determine the vertical elevations and their time histories of water levels, wave runup and water overtopping of the levee systems for specific areas of interest within the New Orleans region.  Various hydraulic and hydrodynamic model simulations including HEC-GeoRas, HEC-Ras, RMA2 and ADCIRC were required to characterize local hydrodynamics, internal drainage and flooding as well as levee performance.  An extensive data collection and analysis was conducted to identify additional data needs to be collected for the engineering analysis.


Las Gallinas Creek H&H & Coastal Analysis, Marin County, California

NCI performed and analysis to develop the riverine and coastal floodplain maps for the without project existing (year 0) condition and the without project future (year 50) condition.  The performance of the flood control project was also evaluated using the risk and uncertainty method.

The tasks performed for the H&H analysis included: collecting and reviewing the hydrological and hydraulic data, tidal stages, and topographic/bathymetric data; developing a Digital Elevation Model (DEM) by merging the channel cross section survey and the levee profile survey into the County's DEM; developing a HEC-RAS model for the South Fork of Las Gallinas Creek and adjacent floodplains, with the geometric data being derived using HEC-GeoRAS; conducting riverine hydraulic modeling and floodplain delineation using the HEC-RAS and HEC-GeoRAS models, and developing riverine floodplain maps for eight flood events for both the year 0 and the year 50 conditions; estimating uncertainties in water surface elevations considering the uncertainties in HEC-RAS model parameters; computing the conditional non-exceedance probabilities for the 100-year flood event; and evaluating the project performance based on the freeboard requirements for the 90% or 95% probability of non-exceedance.

The tasks performed for the coastal analysis included: conducting tidal statistic analysis, and deriving tidal frequency curve for the project site; estimating sea level rise based on the historic trend and on the USACE guidance (EC 1165-2-211), and developing the resulting tidal frequency curve in year 50; conducting wave hindcasting and determining return wave conditions in San Pablo Bay; determining wave conditions at the project site by transforming waves from the Bay to the site and by including the local wind waves generated within the marshland; computing wave runup, wave overtopping rate and cumulative water volume for eight coastal storm events considering the difference in levee characteristics; and determining the coastal inundation water levels, and developing the coastal inundation floodplain maps for eight coastal storm events for both the year 0 and the year 50 conditions.


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