Lessons Learned from Integrating 1D and 2D Riverine and Collection System Models

Many communities in Virginia and across the country suffer from routine and often severe flooding due to a combination of riverine impacts and old, undersized stormwater collection systems. But how many communities have the opportunity to developed detailed hydrologic and hydraulic models of both systems on a watershed scale? The City of Fayetteville NC had the vision and financial commitment to analyze drainage issues across all 12 of its watersheds located within the City.

Arcadis was tasked with supporting the City and its program manager Freese and Nichols with performing detailed modeling of the Blounts Creek Watershed. With its 7.0 square mile area and a stream length of 9.0 river miles, it is the largest and most developed of the City’s watersheds. Work included developing detailed 1D and 2D hydrologic and hydraulic models using HEC-HMS/HEC-RAS for the primary (riverine) system and ICM for the secondary (collection) system; performing a field assessment of high priority stream reaches and identifying issues and problem areas that require mitigation with new drainage solutions.

To successfully develop, validate, and integrate the 1D and 2D riverine and collection system models within such a short timeframe, the Arcadis team needed to utilize all available resources efficiently and effectively. One of the key methods used by the Arcadis team to best schedule time and resources was to couple hands-on practices with automated methods when developing the hydrologic and hydraulic model parameters. In reviewing the Standards Manual provided by the City, the Arcadis team noted places where automated tools could streamline parameter development. For example, the team created an ESRI based tool that could calculate the times of concentration for all the subcatchments and provide the data in a format that would be directly imported into InfoWorks ICM. In tandem, to ensure a quality product, the modeling team leads developed extensive QA/QC procedures for the modelers to use to validate the output from the tools.

This presentation will step through the overall program and vision of the City in establishing and implementing the watershed master plan program and Arcadis’ process of coupling automated processes with hands-on practices to develop, validate, and integrate the 1D and 2D riverine and collection system models within such a short timeframe.