Details:

Creators:
Janke, Ben ; Gulliver, John S. ; Wilson, Bruce N.
Janke, Ben ; Gulliver, John S. ; Wilson, Bruce N. Less -
Corporate Creators:
St. Anthony Falls Laboratory
Corporate Contributors:
University of Minnesota. Center for Transportation Studies
Subject/TRT Terms:
[+]
Aggressive Waters, Watersheds Drainage Practices Impervious Area, Moisture Barriers, Runoff, Stormwater, Moisture Barriers Runoff Surface Drainage Watersheds
Publication/ Report Number:
CTS 11-20
Resource Type:
Tech Report
Geographical Coverage:
Minnesota
Corporate Publisher:
University of Minnesota. Center for Transportation Studies
Abstract:
Practitioners responsible for the design and implementation of stormwater management practices rely

heavily on estimates of impervious area in a watershed. However, the most important parameter in determining

actual urban runoff is the “effective” impervious area (EIA), or the portion of total impervious area that is directly

connected to the storm sewer system. EIA, which is often considerably less than total impervious area and can vary

with rainfall depth and intensity, is likely not determined with sufficient accuracy in current practice. A more

accurate determination of EIA in a watershed would benefit a wide range of organizations involved in the design of

stormwater management, pollution prevention, and transportation structures.

This study investigated two existing methods of estimating EIA in a watershed: (1) analysis of large

rainfall-runoff data sets using the method of Boyd et al. (1994), and (2) overlay analysis of spatial (GIS) data,

including land cover, elevation, and stormwater infrastructure, using the method of Han and Burian (2009). The

latter method provides an estimate of connected pavement, but requires the user to input the value of connected

rooftop to determine the actual EIA value, which is the sum of these two quantities. The two methods were applied

to two urban catchments within the Capitol Region Watershed in St. Paul, MN. The results were used to evaluate

the potential of each method and make recommendations for future studies.

In summary, the data analysis technique (Boyd et al., 1994) has the advantage of being quick and relatively

simple to implement, as it did not require familiarity with specialized software tools (e.g. ArcGIS) and could be

completed with any spreadsheet program with graphing capabilities (e.g. Excel). The EIA estimates from the data

analysis are the most accurate, but the technique is unable to determine where in the watershed the EIA is located,

and cannot be used if runoff discharge and local precipitation data is unavailable. By contrast, the GIS method

(Han and Burian, 2009) has the advantage of being applicable to un-gauged watersheds, and also provides the

location of EIA in the watershed. This latter feature makes it particularly attractive for honing the development and

placement of BMP’s in a watershed. Unfortunately, the accuracy of the GIS method is completely dependent on the

ability to faithfully represent the amount of roof connection in a watershed, a process that can add significant time

and expense to the EIA estimate.


Format:
PDF
Funding:
CTS Project #2011076
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:10f120cf127be4fd59a842c826500375d2b72864602ddc9aac531c6722c3135a
Download URL:
https://rosap.ntl.bts.gov/view/dot/23247/dot_23247_DS1.pdf
File Type:

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