From: Technology and Information Management
Counting the Small Stuff
Portland, OR, also has a combined
sewer system. For 20 years, the city has worked to reduce combined sewer
overflows to the Willamette River and the Columbia Slough. Managing stormwater
inflows can reduce peak flows to avoid overload of the system and prevent sewer
backups into homes, and modeling the system accurately is critical. The city’s
Bureau of Environmental Services (BES) sought a way to accurately model the
system to account for such features as street inflow controls, local detention
and retention systems, and even the effects of increased tree canopy in the
city.
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The effects of these small-scale,
local features are not adequately taken into account in “lumped” models, which
might include only pipes of at least 12 inches in diameter or larger. BES
realized it needed a model that would account for more features, and in the
1990s began developing the Explicit Model Generator, Analysis, and Alternative
Tool Set (EMGAATS), which allows it to simulate local rainfall, runoff,
impervious and pervious conditions, onsite flow routing, and sewer flooding
conditions. The core modeling engine for EMGAATS is xpswmm from XP Software
Inc.
An “explicit” model, unlike a
lumped model, is developed from actual sewer segments, without aggregating
segments the way other models do. Hydraulic elements such as diversion
structures and pumps are taken into account. Subcatchments can be split up to
track overland and piped flows to determine how flows are reaching—or being
diverted from—the sewer system. Containing more system elements—perhaps hundreds
where a lumped model would include dozens—the explicit system can also capture
and model the effects of such things as increased tree canopy, curb cuts,
swales, and other vegetated areas.
Buyers Guide 2010
From: Technology and Information Management
Counting the Small Stuff
Portland, OR, also has a combined
sewer system. For 20 years, the city has worked to reduce combined sewer
overflows to the Willamette River and the Columbia Slough. Managing stormwater
inflows can reduce peak flows to avoid overload of the system and prevent sewer
backups into homes, and modeling the system accurately is critical. The city’s
Bureau of Environmental Services (BES) sought a way to accurately model the
system to account for such features as street inflow controls, local detention
and retention systems, and even the effects of increased tree canopy in the
city.
The effects of these small-scale,
local features are not adequately taken into account in “lumped” models, which
might include only pipes of at least 12 inches in diameter or larger. BES
realized it needed a model that would account for more features, and in the
1990s began developing the Explicit Model Generator, Analysis, and Alternative
Tool Set (EMGAATS), which allows it to simulate local rainfall, runoff,
impervious and pervious conditions, onsite flow routing, and sewer flooding
conditions. The core modeling engine for EMGAATS is xpswmm from XP Software
Inc.
An “explicit” model, unlike a
lumped model, is developed from actual sewer segments, without aggregating
segments the way other models do. Hydraulic elements such as diversion
structures and pumps are taken into account. Subcatchments can be split up to
track overland and piped flows to determine how flows are reaching—or being
diverted from—the sewer system. Containing more system elements—perhaps hundreds
where a lumped model would include dozens—the explicit system can also capture
and model the effects of such things as increased tree canopy, curb cuts,
swales, and other vegetated areas.