Methodology
USGS Highway ZZ Gage
USGS Oil Tank Gage
Village of Bellevue
GeoSWMM model
for the East River watershed
To perform the simulation, I build a East River watershed model using GeoSWMM. The GeoSWMM is a GIS-based version of EPA SWMM and it can create SWMM objects in Arcmap, which is more convenient. I delineate the subcatchment to represent each subwatershed, and connect them with junctions and conduits, and set up the outfall at the mouth of the East River.
Precipitation event
Precipitation event
Downstream water stage
Backwater effect
I investigate the impacts of backwater by running an actual rainfall event on Oct 22 in 2020. I use the precipitation data at the USGS gage at Hwy ZZ and use the water level data at the USGS oil tank as the downstream boundary condition. I run two cases. First, the flow is routed by the Kinematic wave transform method, which does not consider the backwater effect due to downstream water level fluctuations. Second, the flow is routed by Dynamic Wave transform, which considers the backwater effect.
Case 1: Kinematic Wave Routing (without backwater effect)
Case 2: Dynamic Wave Routing (with backwater effect)
Stormwater effect
To investigate the stormwater effect, I create an idealized stormwater drainage system at the Village of Bellevue based on their storm sewer map. I run the rain event of frequency storm of 10-year, 50-year, and 100-year events, retrieved from NOAA Atlas 14 data. I change the pipe from 18 inches to 72 inches to see its impact on water conveyance.