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Assessments and Development of Protocols for Ncdot Stormwater Outlets to Minimize Erosion.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Assessments and Development of Protocols for Ncdot Stormwater Outlets to Minimize Erosion./
Author:	Waickowski, Sarah Elizabeth.
Description:	1 online resource (476 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 85-01, Section: A.
Contained By:	Dissertations Abstracts International85-01A.
Subject:	Water quality. -
Online resource:	click for full text (PQDT)
ISBN:	9798379880552

Assessments and Development of Protocols for Ncdot Stormwater Outlets to Minimize Erosion.
Waickowski, Sarah Elizabeth.

Assessments and Development of Protocols for Ncdot Stormwater Outlets to Minimize Erosion. - 1 online resource (476 pages)

Source: Dissertations Abstracts International, Volume: 85-01, Section: A.

Thesis (Ph.D.)--North Carolina State University, 2023.

Includes bibliographical references

Sediment pollution is a worldwide concern, and stormwater conveyance networks contribute to stream degradation and instability either through direct discharges of sediment or by eroding gullies downslope of pipe outlets. To limit erosion downslope of stormwater pipe outlets, current North Carolina regulations require designers to limit the peak velocity for the 10-yr, 24-hr storm event to the permissible velocity for the downslope soils'; otherwise the conveyance system must be redesigned. This study assessed 60 pipe outlets draining highway and non-highway areas in the Piedmont and Mountain physiographic regions of North Carolina to identify which watershed and downslope characteristics influence the severity of erosion caused by stormwater pipe outlets. The effectiveness of the current standard was also assessed. Six assessed sites in Raleigh were additionally monitored for hydrologic, hydraulic, and water quality impacts.A proposed channel evolution model (CEM) was developed from the 60 site assessments. The proposed five stages of degradation progress from an absence of erosion from the pipe outlet to the point of outfall to a receiving surface water (e.g., stream) (Stage I) to a headcut that has eroded to an impermeable layer as well as migrated to the pipe outlet and mass wasting is occurring (Stage V). Future research is needed to validate the CEM.Results from the assessments suggest the current practice of limiting the 10-yr, 24-hr velocity to the permissible velocity does not sufficiently protect against downslope erosion. Forty-eight of the 60 pipe outlets had erosion from the pipe outlet to the outfall (stream). The 12 sites that exhibited little to no erosion had heavy stands of mixed herbaceous and grassed vegetation, a lack of clustered trees, and a large percentage (> 50%) of moderately permeable hydrologic soil group (HSG) B soils downslope of the outlets.erosion. Forty-eight of the 60 pipe outlets had erosion from the pipe outlet to the outfall (stream). The 12 sites that exhibited little to no erosion had heavy stands of mixed herbaceous and grassed vegetation, a lack of clustered trees, and a large percentage (> 50%) of moderately permeable hydrologic soil group (HSG) B soils downslope of the outlets.Hydrologic data collected from the six sites were modelled to quantify the hydraulic impacts. The potential maximum erosion rate from ranged from 1.54*10-4 to 0.11 cm/s per storm event and indicate designers should include the erodibility of the soils downslope of pipe discharge points in their hydraulic analyses. The mean peak velocities ranged from 0.55 to 3.27 m/s and exceeded the permissible velocity referenced in North Carolina regulations at least 10 times during the 13-month monitoring period, despite none of the storms exceeding the sites' 10-yr, 24-hr rainfall depth. The gullies downslope of the pipe outlets eroded between 2 and 55 m3of soil. Given the magnitude of erosion downslope of the pipes and reoccurring exceedance of the permissible velocity, limiting the peak velocity for the 1-yr, 24-hr storm event to the permissible velocity may be a more effective standard to protect against downslope erosion.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798379880552Subjects--Topical Terms:

569474
Water quality.
Index Terms--Genre/Form:

554714
Electronic books.

Assessments and Development of Protocols for Ncdot Stormwater Outlets to Minimize Erosion.
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245 1 0 $a Assessments and Development of Protocols for Ncdot Stormwater Outlets to Minimize Erosion.
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500 $a Source: Dissertations Abstracts International, Volume: 85-01, Section: A.
500 $a Advisor: Heitman, Joshua L.;Doll, Barbara A.;Hunt, William F.
502 $a Thesis (Ph.D.)--North Carolina State University, 2023.
504 $a Includes bibliographical references
520 $a Sediment pollution is a worldwide concern, and stormwater conveyance networks contribute to stream degradation and instability either through direct discharges of sediment or by eroding gullies downslope of pipe outlets. To limit erosion downslope of stormwater pipe outlets, current North Carolina regulations require designers to limit the peak velocity for the 10-yr, 24-hr storm event to the permissible velocity for the downslope soils'; otherwise the conveyance system must be redesigned. This study assessed 60 pipe outlets draining highway and non-highway areas in the Piedmont and Mountain physiographic regions of North Carolina to identify which watershed and downslope characteristics influence the severity of erosion caused by stormwater pipe outlets. The effectiveness of the current standard was also assessed. Six assessed sites in Raleigh were additionally monitored for hydrologic, hydraulic, and water quality impacts.A proposed channel evolution model (CEM) was developed from the 60 site assessments. The proposed five stages of degradation progress from an absence of erosion from the pipe outlet to the point of outfall to a receiving surface water (e.g., stream) (Stage I) to a headcut that has eroded to an impermeable layer as well as migrated to the pipe outlet and mass wasting is occurring (Stage V). Future research is needed to validate the CEM.Results from the assessments suggest the current practice of limiting the 10-yr, 24-hr velocity to the permissible velocity does not sufficiently protect against downslope erosion. Forty-eight of the 60 pipe outlets had erosion from the pipe outlet to the outfall (stream). The 12 sites that exhibited little to no erosion had heavy stands of mixed herbaceous and grassed vegetation, a lack of clustered trees, and a large percentage (> 50%) of moderately permeable hydrologic soil group (HSG) B soils downslope of the outlets.erosion. Forty-eight of the 60 pipe outlets had erosion from the pipe outlet to the outfall (stream). The 12 sites that exhibited little to no erosion had heavy stands of mixed herbaceous and grassed vegetation, a lack of clustered trees, and a large percentage (> 50%) of moderately permeable hydrologic soil group (HSG) B soils downslope of the outlets.Hydrologic data collected from the six sites were modelled to quantify the hydraulic impacts. The potential maximum erosion rate from ranged from 1.54*10-4 to 0.11 cm/s per storm event and indicate designers should include the erodibility of the soils downslope of pipe discharge points in their hydraulic analyses. The mean peak velocities ranged from 0.55 to 3.27 m/s and exceeded the permissible velocity referenced in North Carolina regulations at least 10 times during the 13-month monitoring period, despite none of the storms exceeding the sites' 10-yr, 24-hr rainfall depth. The gullies downslope of the pipe outlets eroded between 2 and 55 m3of soil. Given the magnitude of erosion downslope of the pipes and reoccurring exceedance of the permissible velocity, limiting the peak velocity for the 1-yr, 24-hr storm event to the permissible velocity may be a more effective standard to protect against downslope erosion.
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538 $a Mode of access: World Wide Web
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650 4 $a Sedimentary geology. $3 1183087
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