EPA SWMM AND XPSWMM INVESTIGATION

BEE 549Tracy ArrasMarch 2011

Objectives

Utilize EPA SWMM to understand basic runoff modeling for a small urban area

SWMM is public software Designed for modeling storm water in urban areas Lumped model Source code available

Utilize XPSWMM to investigate a coupled 1D/2D model for flood analysis

XPSWMM is not a public software No source code Designed for modeling of storm water, sanitary and river

systems in urban areas

Albany, Oregon

Population ~49,000Elevation: 180-430 ftUrban area & pasture/hay edgesDrains to Willamette River

GIS DATA

LiDAR – Bare ground 3ft resolution 10 M DEM STATSGO SOIL USGS 2001 LAND COVER NHD PLUS STREAMS ½ Meter 2005 Orthophotography City of Albany GIS – streets, buildings, ditches, etc.

Creation of Catchments: ArcHydro Method

LiDAR could not be used because detects urban features and delineates small catchments…

Catchments Defined from LiDAR (3ft)

Catchments Defined with 10 m DEM Final

catchments based on drainage pattern… may not be correct.

Southern part by canal ?

STATSGO – SOIL DATA

• Uses MS ACCESS for DB• Not user friendly• Soil in study area:

• Silt Loam• Ksat high - 14.5 in/hr• Ksat rep – 9 in/hr• Ksat low – 4 in/hr

Project Characteristics14 Catchments defined usingArcHydro methodology

Catchments drain to USGS Periwinkle Creek gauge

Terrain relatively flat: 152-262

Periwinkle Creek runs through

Land use: 85% residential9% pasture/hay5% open space1% water/wetlands

2 USGS stream gauges with only one or two flow measurements

City of Albany 5 min gauge hts

EPA SWMM

Precipitation used March 25-31, 2010Storm Event

15 minute gauge data Located Albany Waste Water Treatment Plant

FlowFlow determined fromGauge height and Manning’s n.

Note: Manning’s n determined From channel geometry and a single USGS flow measurement.

Outflow for catchments

Sensitive Parameter Hydraulic Conductivity – not sensitive

WIDTH of overland flow – very sensitive! (area divided by longest overland flow length)

Width - in an urban area typically is the distance from the back of the lot to the center of the street

Width –often a calibration parameter whose value is adjusted to produce a good between observed and modeled hydrograph

XPSWMM – 2D Investigate a coupled 1D/2D model for flood

analysis along Periwinkle Creek, Albany, Oregon

TIN and Inflow Boundary Location From LiDAR create TIN, import in XPSWMM Create DTM Create Inflow Boundary Conditions

Flow 2D Boundary Conditions

Results of Runoff Model - 2D Only

Ponding due to DTM

Cross-Sections at Ponding Location

Cross-Sections at Ponding Location

Culvert Locations or 1D Elements

1D Culverts in a 2D Model

1D Elements and Parameters

Coupled 1D/2D Model

2D – DTM from LiDAR

1D – Culverts

Inlet Flow Boundary Conditions

Outlet Flow Conditions

Analysis with 1D/2D model

Flow Through each Culvert

Simulated Flooding with Coupled 1D/2D

MOVIE

Cell Size in Coupled 1D/2D SystemMax flow (cfs)

Cell Size 20 ft 10 ft 8 ft 5ft

Conduit1 91.8035 91.142 91.6966*

Conduit2 69.8512 71.4768 71.6581*

Conduit3 41.8063 50.7645 50.0546*

Total flow (ft^3)

Cell Size 20 ft 10 ft 8 ft 5 ft

Conduit1 288,103.40 308,075.19 310,451.04*

Conduit2 132,314.04 155,898.72 157,757.59*

Conduit3 38,100.80 71,798.10 71,867.65*

Questions

Manning’s n can be calculated from channel geometry and a single USGS flow measurement…

Flow can be calculated from Manning’s n and gauge height but…

Can a model be calibrated and verified using flow data calculated in this manner? Can it be defended?

Future Work

Test different grid resolutions on hydrographs over conduits

Investigate time steps…courant numbers Test changing stream to 1D with defined channel Model urban 1D/2D to incorporate storm drains

and conduits 5 m resolution—error—exceed maximum 2D cell

count 1,000,000!!!