Catchment Conundrum: Pros and Cons of Rain-on-Grid Modeling the Nashawannuck Brook Restoration in Northampton, MA
Rosalie Starvish, MS, PE, CFM, CPMSM
GZA GeoEnvironmental Inc.
Springfield, MA
Rex S. Gamble, EIT
GZA GeoEnvironmental Inc.
Norwood, MA
Authors: Starvish, Rosalie, MS, PE, CFM, CPMSM, Gamble, Rex S., EIT
The City of Northampton in Massachusetts purchased the former Pine Grove Golf Course with the intention to improve climate resiliency by restoring the Nashawannuck Brook’s natural hydrology through a combination of targeted reforestation, soil aeration, and removal of anthropogenic drainage features. GZA performed holistic conceptual level (~25%) restoration design of 0.7 miles of Nashawannuck Brook, which included geomorphic assessment, ecological conditions assessment, and hydrologic and hydraulic modeling. This presentation focuses on the hydrologic and hydraulic modeling performed by GZA to support restoration design of Nashawannuck Brook for the present day and future projected flows.
Hydrology and hydraulics (H&H) are closely linked fields of study that are both usually required in the analysis and/or design of stream restoration. Hydrology examines watershed characteristics and applies conservation of mass to provide the engineer/scientist with the quantity and timing of flow to a site in response to precipitation.
Hydraulics applies both conservation of mass and conservation of momentum to provide the engineer/scientist with flow characteristics at the site such as elevation, depth, and velocity. Traditionally, these two fields required separate models, for example, HEC-HMS for hydrology and HEC-RAS for hydraulics. However, due to leaps and bounds in computational power in the 21st century, it is now possible to perform both hydrological and hydraulic analyses in one platform using a rain-on-grid model. Despite the many advantages of streamlining the H&H process into one model, it is unclear whether rain-on-grid modeling results converge with those of traditional H&H modeling.
GZA applied both a rain-on-grid model in 2D HEC-RAS and traditional H&H modeling with HEC-HMS and 2D HEC-RAS to the Nashawannuck Brook stream restoration in Northampton, MA. In this presentation, GZA will explore the differences, advantages, and disadvantages between the two H&H approaches and discuss the implications of these modeling methodologies on project permitting and design.
About Rosalie Starvish
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About Rex S. Gamble
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