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Journal of Cold Regions Engineering / Volume 21 / Issue 1 / TECHNICAL PAPERS

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Assessing the Performance of a Sloped-Block Ice-Control Structure

J. Cold Reg. Eng. 21, 19 (2007); http://dx.doi.org/10.1061/(ASCE)0887-381X(2007)21:1(19) (21 pages)

J. H. Lever1 and G. Gooch2

1Mechanical Engineer, U.S. Army Cold Regions Research and Engineering Laboratory (CRREL), 72 Lyme Rd., Hanover, NH 03755 (corresponding author). E-mail: james.h.lever@erdc.usace.army.mil
2Civil Engineering Technician,U.S. Army Cold Regions Research and Engineering Laboratory (CRREL), 72 Lyme Rd., Hanover, NH 03755.

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(Submitted 11 January 2006; accepted 20 March 2006)

Hardwick, Vt., having experienced 10 ice-jam floods in 30 years, has not experienced one since construction of a sloped-block ice-control structure (ICS) in 1994. This innovative structure consists of four sloped granite blocks spaced across the Lamoille River upstream of the village and adjacent to a treed floodplain. It arrests ice runs, forms partially grounded jams, and retains these jams for hours to days. The measured ice-hydraulic characteristics of the breakup runs and resulting ice jams (e.g., wave celerities and amplitudes, porous-flow seepage coefficients) are similar to characteristics obtained from the 1:10-scale model tests used to develop the structure. Seepage coefficients, and hence jam porosities, generally increase with increasing discharge, and only two breakup events have caused floodplain flow. Water temperatures of 0.1–0.3°C measured during a breakup event confirm that ice melting can account for the rate of porosity increase. Field and model data indicate that ice-jam holding time and jam-release discharge increase with increasing ice-piece thickness to a threshold of 6–7% of ICS gap width, beyond which no releases occur. Consistency between prototype and model ice-hydraulic characteristics and ice-holding capacity reinforce the conclusion that the sloped-block ICS can reliably retain ice jams during breakup events that pose the greatest flood threat: thick, strong ice, and large breakup waves. This ice-retention behavior can account for the observed reduction in ice-jam flooding in Hardwick during the past 11 seasons.

© 2007 ASCE

Acknowledgments

Nearly everyone in CRREL’s Ice Engineering Group has contributed over the years to the design, construction, and monitoring of the sloped-block ice-control structure: J.C. Tantinclaux, Kate White, Steve Daly, Andy Tuthill, Ed Foltyn, John Gagnon, Charlie Clark, Bob Haehnel, Jesse Stanley, and Carrie Vuyovich. The writers sincerely thank them for their efforts and continued interest in the project. The Town of Hardwick and the Federal Emergency Management Agency split the construction cost of the prototype ICS, and Hardwick continues to maintain it. We also gratefully acknowledge the support of the U.S. Army Corps of Engineers civil works research program for initial development and continued monitoring of the ICS.

Article Outline

  1. Introduction
  2. Ice-Control Structure
  3. Hardwick Ice-Jam Flooding
  4. Ice-Hydraulic Characteristics of Specific Events
  5. Through-Jam Flow
  6. Water Temperature and Ice Melting
  7. ICS Ice-Holding Performance
  8. Discussion and Conclusions

KEYWORDS

ASCE SUBJECT HEADINGS

Ice jams, Porous flow, Seepage, Hydraulics

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ARTICLE DATA

Digital Object Identifier
http://dx.doi.org/10.1061/(ASCE)0887-381X(2007)21:1(19)

PUBLICATION DATA

ISSN

0887-381X (print)  
1943-5495 (online)

Publisher

ASCE

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