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1D and 1D/2D Floodplain Mapping Projects Using HEC-RAS and MIKE Flood, Greater Toronto Area, Ontario

Valdor Engineering Inc. has completed numerous private and public sector projects regarding floodplain mapping (FPM).  Historically, in Ontario, one-dimensional (1D) hydraulic modelling using the US Army Corps’ HEC-2 and HEC-RAS has been the standard approach to modelling riverine systems for the purpose of calculating the extent of flooding and for preparing floodplain mapping.  In confined, channelized drainage systems, 1D hydraulic modelling continues to be a reliable and standard approach.  More recently, however, the use of sophisticated one-dimensional//two-dimensional (1D/2D) hydraulic 

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Etobicoke Creek Sheet 24 - 350yr Floodli

Selected FPM Projects Using HEC-RAS (1D)

  • Cooksville Creek Flood Mitigation Analysis and FPM

  • Downtown Brampton Floodplain Mapping Update

  • Mount Pleasant Subdivision Floodplain Mapping

  • Gateway Lindsay Subdivision Floodplain Mapping

  • Massey Creek Flood Reduction Study and FPM Update

  • Falcon Creek Hydrology and Hydraulics Study

  • Cobourg Creeks Hydraulic Analysis and Floodline Mapping

  • Pine and Dunbarton Creeks Hydrology and FPM Update

  • Fenelon Falls Drainage Study (Basin DD),

  • King City Subdivision Floodplain Mapping

  • Thornridge Drive Flood Study

  • Chandni Garden Hydraulic Study and Stormwater Management

  • Nonquon River Subwatershed Study and FPM Update

  • 5549 Aurora Road Flood Study and FPM

  • Ashborough Village Floodplain Mapping

  • Moco Subdivision Floodplain Mapping

  • Corseed Subdivision Floodplain Mapping

Selected FPM Projects Using MIKE Flood (1D/2D)

  • Pickering/Ajax SPA Hydraulic Assessment and FPM Update

  • Bolton Berm Remediation Study and Floodplain Mapping Update

  • Jane St and Wilson Ave Hydraulic Update and Floodplain Mapping

  • Yonge Street and Elgin Mills Road Area Floodplain Mapping Update

  • Lower Humber River 2D Hydraulic Study and Floodplain Mapping

Fig 4.1 Intermediate Development Step fo

models such as MIKE Flood are becoming the preferred method for calculating the extent of

the floodplain in areas where the floodplain is poorly defined with multiple braided channels and spills as is often the case in older

developed areas within the existing floodplain and including 

many Special Policy Areas (SPA’s).  The 1D/2D coupled models, such as MIKE Flood, are typically developed using detailed surface topography derived from LiDAR and GIS-based land use information regarding both developed and undeveloped areas.  Grid or mesh units can be

finely set with coverage often in the order of a few square meters

and dynamic hydraulic calculations are completed within each unit typically for flow depth, flow velocity and flow direction.  The 1D/2D modelling is particularly useful in characterizing the details of flooding under complex hydraulic conditions and for designing and evaluating flood mitigation solutions with confidence.

Project Profile - Water Resources
VALDOR ENGINEERING INC.
Consulting Engineers & Project Managers
VALDOR
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Downtown Brampton Floodplain Mapping Update,

Brampton, Ontario

Client: Toronto and Region Conservation Authority

As parallel process to the City of Brampton’s “Phase 2: Integrated Riverine and Urban Flood Risk Analysis and Urban Drainage Study”, the TRCA retained Valdor Engineering Inc. to complete a floodplain mapping update using HEC-RAS and ArcGIS for the Downtown Brampton Special Policy Area (SPA) including recent LiDAR topographic information, as well as the results from the 2013 Etobicoke Creek Floodplain Mapping Update.  Requested tasks also included an assessment of the interaction between the Brampton by-pass channel and the downtown Brampton Flood Damage Centre (FDC) to determine an appropriate flow partitioning “split flow” approach for the Regional (Hurricane Hazel) and 350 year storms.  The results from this study will establish the interim floodplain regulation limits within Downtown Brampton and the model will ultimately be used as the base model for the development of the 1D/2D integrated flood model as defined in the City of Brampton’s “Phase 2: Integrated Riverine and Urban Flood Risk Analysis and Urban Drainage Study”.

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Figure C.2 - HEC-RAS Schematic Regional.
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Etobicoke Creek Sheet 24 - Regional Floo
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Project Profile - Water Resources
VALDOR ENGINEERING INC.
Consulting Engineers & Project Managers
VALDOR
Valdor 1992 Logo.JPG

Lower Humber River 2D Hydraulic Study and Floodplain Mapping, Toronto

Client: TRCA and City of Toronto

Valdor Engineering Inc. was retained by the TRCA and the City of Toronto to undertake a two-dimensional (2D) flood study using the available LiDAR topographic survey, field survey and land use details to re-evaluate existing 1D flood line limits and elevations and to assess the flood vulnerability of the Humber Waste Water Treatment Plant from both a regulatory and operational perspective.  The 1D open channel/closed conduit flow network was modelled using the Mike 11 Hydrodynamic Modelling system. The 2D overland flow area was modelled using the Mike 21 Hydrodynamic Modelling system.  The 1D and 2D models were then coupled using the Mike model manager. The Mike model manager (Zero/Flood/Urban etc.) is a state-of-the-Art sophisticated hydrodynamic modelling system that allows appropriate and accurate modelling of complex

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topographic and urban features such as buildings, roadways, surface and underground conduits, wide range of hydraulic structures including open channels, ponds, lakes and estuaries.  The primary outputs of the 1D/2D couple model were flood depth, velocity, flood flow direction, which were used to prepare flood depth maps, water surface elevation maps, flood flow direction maps and video-animations, velocity maps and flood line maps. The 1D/2D coupled hydraulic model was very effective to identify the extent and depth of spill that occurs in the vicinity of a group of road and rail crossings that could not be characterized accurately with the previous model due to inherent 1D modelling limitations. A limited 

number of observed data was used for verification of the flood extent and depth that showed good agreement with the simulated results.

Project Profile - Water Resources
VALDOR ENGINEERING INC.
Consulting Engineers & Project Managers
VALDOR
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Jane Street and Wilson Avenue 2D Hydraulic Model Update and Floodplain Mapping, Toronto, Ontario

Client: Toronto and Region Conservation Authority

Valdor Engineering Inc. was retained by the TRCA to undertake a two-dimensional (2D) flood study using the available LiDAR topographic survey, field survey and land use details to develop a coupled Mike Flood model to define the extent of flooding for the 2-yr through 350-yr storm events and Hurricane Hazel, and prepare new engineered floodplain mapping for the study area.  The study area along Black Creek extended from Gravenhurst Avenue to downstream of Lawrence Avenue.  The main objectives of the study included an assessment of the extent of flooding for future use in the regulation area and to identify the causes of flooding to further inform other technical studies being undertaken in the study area.  As a result of limitations of the HEC-RAS modelling used in the previous floodplain mapping, spills, split flow conditions, and the extent of

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5.2 Flood Risk Map and Legend - combined
Fig 6.1 - Regional Flood Flow - Heavitee

flooding throughout the study area were never well accounted for or assessed.  A better understanding was required regarding flooding effects on adjacent land use decisions, the development of appropriate flood proofing standards, as well as the assessment of flood risk conditions.  Due to the complex hydraulics including multiple spill locations and flow directions, and flow around buildings, the capabilities of the HEC-

RAS model were not adequate to accurately account for these conditions and a sophisticated two-dimensional (2D) model was required.  The

existing reach of Black Creek is concrete lined and not sufficiently sized to convey the Regional flow which results in widespread

flooding through the flat developed area adjacent the watercourse.  Project tasks included the preparation of a coupled 1D / 2D Mike Flood model for the study area including model

validation, comparison of results with the existing HEC-RAS model, characterization and risk assessment of the floodplain, identification of hydraulic constraints, preparation of a technical report, preparation of digital engineered floodplain mapping and flood scenario video animations, and a one-day training session for the client.

Project Profile - Water Resources
VALDOR ENGINEERING INC.
Consulting Engineers & Project Managers
VALDOR
Valdor 1992 Logo.JPG