FM Metro Basin-Wide Modeling Approach
The purpose of this study was to create a consistent set of HEC-HMS models for tributaries within the Red River of the North basin to assist in development and analysis of future flood damage reduction projects. The HEC-HMS models were developed as a planning tool that would enable users to evaluate existing and proposed water management projects and as a starting point for more expansive watershed modeling. The models are parameterized for rainfall runoff modeling and not snowmelt modeling. A 100-yr, 10-day runoff senario was utilized to identify non-contributing drainage area as part of this study. Consequently, the non-contributing drainage areas within each subwatershed may be underestimated for more moderate events. The hydrologic routing adopted as part of this study is based on roughly cut cross section data and coarsely constructed HEC-RAS models (without bridges, ineffective flow refinements, or hydraulic calibration that would normally be necessary for a detailed hydraulic study). Adding further detail to routing parameters should be considered before adopting this suite of models. Simplifying assumptions were utilized to model major hydraulic structures as part of this study. When reservoir operation is critical, a HEC-ResSIM model should be adopted in conjunction with the HEC-HMS model for a given subwatershed. The HEC-HMS models are not meant to be utilized for snowmelt modeling, forecasting, continuous simulation modeling, or for use in developing flow-frequency analysis without further refinement and calibration.
The scope of the study consisted of performing terrain analysis on LiDAR data to determine HEC-HMS modeling parameters, calibration, and synthetic model development. LiDAR data from the Red River Basin Mapping Initiative was generalized into a 5 meter by 5 meter Digital Elevation Model (DEM). This DEM served as the base for all terrain analysis processing for the project. Project tasks were completed by a team of consulting firms on behalf of the City of Fargo, ND, City of Moorhead, MN, and the US Army Corps of Engineers.
The study was divided into two phases:
Phase 1 got completed in December 2011. Phase 2 got mainly completed in summer 2013 except for the Park River and the Pembina River watersheds which are anticipated to be finished in spring 2014.