Flood Analysis

Flood Frequency Analysis and Flood Mapping With HEC RAS

Project Purpose

The primary objective of this project was to provide a comprehensive hydrological analysis of a river system near Revelstoke, BC, to support a potential land use development. The analysis was carried out in accordance with the EGBC Professional Practice Guidelines on "Legislated Flood Assessments in a Changing Climate in BC" (EGBC, 2018). This analysis aimed to map estimated flood levels for various return periods, ensuring informed decision-making for development planning decisions.

Project Scope and Methodology

Data Collection and Preparation

  1. Elevation Data Integration: Integrated high-resolution (1m) LiDAR data and 30m Digital Elevation Model (DEM) data from the Canadian High-Resolution Digital Elevation Model (HRDEM) to construct an accurate topographic representation of the study area.

Flood Frequency Analysis

  1. Historical Data Review: Compiled and analyzed historical streamflow data to identify patterns and trends.
  2. Frequency Analysis: Conducted statistical analyses to estimate the frequency and magnitude of flood events, focusing on return periods such as 5, 10, 50, 100, and 200-year flood levels.

Hydraulic Modeling

  1. 1D/2D HEC-RAS Unsteady Flow Model Development: Constructed a 1D/2D unsteady flow model using the HEC-RAS software. This model incorporated the high-resolution elevation data and hydrological inputs to simulate water flow dynamics across the river system.
  2. Model Calibration and Validation: Calibrated the model using historical flood data and validated it against known flood events to ensure accuracy and reliability.

Floodplain Mapping

  1. Simulation of Flood Scenarios: Ran multiple simulations to estimate flood extents and depths for various return period flood events.
  2. Flood Hazard Mapping: Created detailed floodplain maps showing estimated flood levels and inundation areas for different scenarios. These maps are critical for assessing the suitability and safety of potential land use developments.

Reporting and Recommendations

  1. Comprehensive Report Preparation: Compiled the analysis results, flood frequency data, hydraulic model outputs, and floodplain maps into a detailed flood hazard assessment report.
  2. Development Recommendations: Provided recommendations for land use planning, ensuring that proposed developments are situated safely outside of high-risk flood zones.

Project Outcomes

  1. Enhanced Understanding of Flood Risks: The project provided a clear and accurate assessment of flood risks in the Revelstoke area, crucial for planning safe and sustainable land use developments.
  2. Detailed Flood Hazard Maps: High-resolution floodplain maps offer valuable insights for developers, planners, and decision-makers, ensuring that land use decisions are based on robust flood risk assessments.
  3. Informed Land Use Planning: The findings and recommendations support the development of safe and sustainable land use strategies, minimizing potential flood impacts on new developments.

By leveraging industry standard hydrological analysis and hydraulic modeling techniques, this project significantly contributes to the understanding of flood hazards in the proposed development area, ensuring that potential land use developments are planned with safety in mind.

References

      1. Engineers and Geoscientists British Columbia. Professional Practice Guidelines -- Legislated Flood Assessments in a Changing Climate in BC. Version 2.1. (2018).

Posted: Jan. 15, 2022
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