Monday, September 9, 2024
10:30 AM - 11:00 AM
Location Name
Modeling the Future of Nashville Stormwater: An Update on the Metro Stormwater Master Plan

Nashville, Tennessee’s Metro Water Services (MWS) is responsible for a stormwater service area of 514 square miles which serves over 700,000 people and is currently divided into 63 sub-basins that includes 95,000 structures. MWS last inventoried the stormwater infrastructure in 2000. In 2022, the City decided to establish a plan to handle increased densities in development and to implement a master plan to prioritize stormwater drainage system improvement projects. Since the beginning of the project in the fall of 2022, the Stormwater Master Plan (SWMP) team has inventoried and assessed the condition of over 20,000 structures as of January 2024. In the summer of 2023, MWS requested that the inventory efforts double with four survey crews in the field. Since then, the survey crews have been able to inventory approximately 300 to 600 structures per week, doubling the previous inventory rate. With the increased inventory effort, challenges have arisen in terms of the quality of the data received that necessitated an organized workflow to make the condition assessment process more streamlined and efficient. In addition, the SWMP team has also developed the existing hydraulic models for five subbasins, which have been presented to the MWS team with proposed alternatives and potential future projects to improve the stormwater system. These hydrologic and hydraulic (H/H) models were developed inside the commercial H/H software PCSWMM and leverage the modeling parameters that are unique to SWMM-based models such as how the basin timing is simulated and options to better represent the overland flow characteristics. This presentation will serve as an update on this county-wide operation. We will present (1) a general update to the project along with lessons learned, (2) condition assessment metrics and challenges, (3) a detailed look into the hydraulic model and alternatives development and (4) the development of a unique decision-making criteria used to rank projects.  Additionally, we will review project-specific tools created for data management. This is an important project to MWS’ ongoing efforts to protect their investments, respond to aging and undersized infrastructure, and prepare for the future growth of Nashville.