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Backfilling canals to mitigate Wetland dredging in Louisiana coastal marshes

Abstract

Returning canal spoil banks into canals, or backfilling, is used in Louisiana marshes to mitigate damage caused by dredging for oil and gas extraction. We evaluated 33 canals backfilled through July 1984 to assess the success of habitat restoration. We determined restoration success by examining canal depth, vegetation recolonization, and regraded spoil bank soils after backfilling. Restoration success depended on: marsh type, canal location, canal age, marsh soil characteristics, the presence or absence of a plug at the canal mouth, whether mitigation was on- or off-site, and dredge operator performance.

Backfilling reduced median canal depth from 2.4 to 1.1 m, restored marsh vegetation on the backfilled spoil bank, but did not restore emergent marsh vegetation in the canal because of the lack of sufficient spoil material to fill the canal and time. Median percentage of cover of marsh vegetation on the canal spoil banks was 51.6%. Median percentage of cover in the canal was 0.7%. The organic matter and water content of spoil bank soils were restored to values intermediate between spoil bank levels and predredging marsh conditions.

The average percentage of cover of marsh vegetation on backfilled spoil banks was highest in intermediate marshes (68.6%) and lowest in fresh (34.7%) and salt marshes (33.9%). Average canal depth was greatest in intermediate marshes (1.50 m) and least in fresh marshes (0.85 m). Canals backfilled in the Chenier Plain of western Louisiana were shallower (average depth = 0.61 m) than in the eastern Deltaic Plain (mean depth range = 1.08 to 1.30 m), probably because of differences in sediment type, lower subsidence rate, and lower tidal exchange in the Chenier Plain. Canals backfilled in marshes with more organic soils were deeper, probably as a result of greater loss of spoil volume caused by oxidation of soil organic matter. Canals ten or more years old at the time of backfilling had shallower depths after backfilling. Depths varied widely among canals backfilled within ten years of dredging. Canal size showed no relationship to canal depth or amount of vegetation reestablished. Plugged canals contained more marsh reestablished in the canal and much greater chance of colonization by submerged aquatic vegetation compared with unplugged canals. Dredge operator skill was important in leveling spoil banks to allow vegetation reestablishment. Wide variation in dredge performance led to differing success of vegetation restoration.

Complete reestablishment of the vegetation was not a necessary condition for successful restoration. In addition to providing vegetation reestablishment, backfilling canals resulted in shallow water areas with higher habitat value for benthos, fish, and waterfowl than unfilled canals. Spoil bank removal also may help restore water flow patterns over the marsh surface. Increased backfilling for wetland mitigation and restoration is recommended.

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Literature cited

  • Adkins, G., and P. Bowman. 1976. A study of the fauna in dredged canals of coastal Louisiana. LA Department of Wildlife and Fisheries Technical Bulletin No. 18. 72 pp.

  • Bahr, L. M., Jr., R. Costanza, J. W. Day, Jr., C. Neill, S. G. Leibowitz, and J. R. Fruci. 1983. Ecological characterization of the Mississippi Deltaic Plain Region: a narrative with management recommendations. US Fish and Wildlife Service, Division of Biological Services. FWS/OBS-82/69.

  • Bozeman, E. L., and J. M. Dean. 1980. The abundance of estuarine larval and juvenile fish in a South Carolina creek.Estuaries 3:89–97.

    Google Scholar 

  • Chabreck, R. H. 1968. Weirs, plugs, and artificial potholes for the management of wildlife in coastal marshes. Pages 178–192in J. D. Newsom (ed.), Proc. Marsh and Estuary Management Symposium, Division of Continuing Education, Louisiana State University, Baton Rouge, LA.

    Google Scholar 

  • Chabreck, R. H. 1979. Winter habitat of dabbling ducksphysical, chemical and biological aspects. Pages 133–142in T. A. Bookhout (ed.), Waterfowl and wetlands—an integrated review. The Wildlife Society,

  • Chabreck, R. H., and C. M. Hoffpauir. 1962. The use of weirs in coastal marsh management in Louisiana.Proc. S.E. Game and Fish Comm. 16:103–112.

    Google Scholar 

  • Chabreck, R. H., and G. Linscombe. 1978. Vegetative type map of the Louisiana coastal marshes. Louisiana Department of Wildlife and Fisheries, New Orleans.

    Google Scholar 

  • Craig, N.J., R. E. Turner, and J. W. Day, Jr. 1979. Land loss in coastal Louisiana (USA).Environmental Management 3:133–144.

    Google Scholar 

  • Davis, D. W. 1973. Louisiana canals and their influence on wetland development. Ph.D. diss., Louisiana State Univ., Baton Rouge. 199 pp.

    Google Scholar 

  • Deegan, L. A., H. M. Kennedy, and C. Neill. 1984. Natural factors and human modifications contributing to marsh loss in Louisiana's Mississippi River deltaic plain.Environmental Management 8:519–528.

    Google Scholar 

  • Fredrickson, L. H., and R. D. Drobney. 1979. Habitat utilization by postbreeding waterfowl. Pages 119–131in T. A. Bookhout (ed.), Waterfowl and wetlands—an integrated review. The Wildlife Society,

  • Gagliano, S. M. 1973. Canals, dredging and land reclamation in the Louisiana coastal zone. Hydrologic and Geologic Studies of Coastal Louisiana, Report No. 14. Center for Wetland Resources, Louisiana State University, Baton Rouge, LA. 104 pp.

    Google Scholar 

  • Gagliano, S. M., K.J. Meyer-Arendt, and K.M. Wicker. 1981. Land loss in the Mississippi River deltaic plain.Transactions Gulf Coast Association Geological Society 31:295–300.

    Google Scholar 

  • Kadlec, J. A., and W. A. Wentz. 1974. State-of-the-art survey and evaluation of marsh plant reestablishment techniques: induced and natural. Contract Report D-74-9. US Army Engineers Waterways Experiment Station, Vicksburg, MI. 2 vols.

    Google Scholar 

  • Larrick, W. D., Jr., and R. H. Chabreck. 1976. Effects of weirs on aquatic vegetation along the Louisiana coast.Proc. Ann. Conf. S.E. Assoc. Fish Wildl. Agencies 30:581–589.

    Google Scholar 

  • Lindall, W. N., Jr., A. Mager, Jr., G. W. Thayer, and D. R. Ekberg. 1979. Estuarine habitat mitigation planning in the southeast. Pages 129–135in G. A. Swanson (ed.), The mitigation symposium: a national workshop on mitigation losses of fish and wildlife habitat. General Technical Report R.-65, Rocky Mountain Forest and Range Exp. Sta., Forest Service, USDSA, Ft. Collins, CO.

    Google Scholar 

  • Longley, W. L., R. Jackson, and B. Snyder. 1978. Managing oil and gas activities in coastal marshes. US Fish and Wildlife Service, Office of Biological Services, FWS/OBS-78/54.

  • Matthews, D. 1983. Checking up on Louisiana's wetlands.Exxon USA 22:12–15.

    Google Scholar 

  • Mendelssohn, I. A., W. B. Sikora, K. L. McKee, and J. P. Sikora. 1984. An evaluation of backfilling canals as a means of mitigating the environmental impact of canals in south Louisiana: vegetation and benthos. Interim Report (phase II) to the Coastal Zone Management Section of the Louisiana Department of Natural Resources, Baton Rouge.

  • Monte, J. 1978. Impact of petroleum dredging on Louisiana's coastal landscape: a plant biogeographical analysis and resource assessment of spoil bank habitats in the Bayou Lafourche Delta. Ph.D. diss., Louisiana State Univ., Baton Rouge. 334 pp.

    Google Scholar 

  • Neill, C., and R. E. Turner. 1987. Comparisons of fish communities in open and plugged backfilled canals in Louisiana coastal marshes.North American Journal of Fisheries Management, 7(1):57–62.

    Google Scholar 

  • Okey, C. W. 1918. The subsidence of muck and peat soils in southern Louisiana and Florida.Transactions of the American Society of Civil Engineers 82:396–422.

    Google Scholar 

  • Perry, G. W. 1976. Standing crops of fishes of an estuarine area in southwest Louisiana.Proc. 30th Annual Southeastern Fish and Wildlife Agencies 30:71–81.

    Google Scholar 

  • Quammen, M. L. 1986. Measuring the success of wetlands mitigation.National Wetlands Newletter 8(5):6–8.

    Google Scholar 

  • Sasser, C. S. 1977. Distribution of vegetation in Louisiana coastal marshes as response to tidal flooding. M.S. thesis, Louisiana State University, Baton Rouge. 40 pp.

    Google Scholar 

  • Scaife, W. W., R. E. Turner, and R. Costanza. 1983. Coastal Louisiana recent land loss and canal impacts.Environment Management 7:433–442.

    Google Scholar 

  • Sikora, W. B., and J. P. Sikora. 1984. Benthos.In R. E. Turner, I. A. Mendelssohn, R. Costanza, K. L. McKee, C. Neill, J. P. Sikora, W. B. Sikora, and E. Swenson, Evaluation of backfilling canals as a means of mitigating the environmental impact of canals. Final Report. Coastal Management Section, Louisiana Department Natural Resources.

  • Snedecor, G. W., and W. G. Cochran. 1967. Statistical methods, 6th ed. Iowa State Univ. Press, Ames. 593 pp.

    Google Scholar 

  • Swenson, E. 1983. Marsh hydrological studies 1982–1983 data report. Coastal Ecology and Fisheries Institute, Center for Wetland Resources, Louisiana State University, Baton Rouge. LSU-CEFI-83-18.

    Google Scholar 

  • Swenson, E. M., and R. E. Turner. In press. Spoil banks: effects on a coastal marsh water level regime.Estuarine, Coastal and Shelf Science.

  • Turner, R. E. 1985. Relationships between coastal land losses and canals and canal levees in Louisiana and management options. Biological Services Program, US Fish and Wildlife Service, Washington, DC. FWS/OBS-85. 71 pp.

    Google Scholar 

  • Turner, R. E., K. L. McKee, W. B. Sikora, J. P. Sikora, I. A. Mendelssohn, E. Swenson, C. Neill, S. G. Leibowitz, and F. Pedrazini. 1983. The impact and mitigation of man-made canals in coastal Louisiana.Water, Science, and Technology 16:497–504.

    Google Scholar 

  • Turner, R. E., and C. Neill. 1984. Revisiting impounded wetlands after 70 years. Pages 309–321in R.J. Varnell (ed.), Water quality and wedand management conference proceedings. New Orleans, LA, August 4–5, 1983.

  • Weinstein, M. P. 1979. Shallow marsh habitats as primary nurseries for fish and shellfish, Cape Fear River, North Carolina.Fisheries Bulletin 77:339–357.

    Google Scholar 

  • Wicker, K. M. 1981. Chenier Plain region ecological characterization: a habitat mapping study. User's guide to the habitat maps. Louisiana Dept. Natural Resources, Baton Rouge, LA. 55 pp. + appendices.

    Google Scholar 

  • Wicker, K. M., and others. 1980. Mississippi Deltaic Plain region ecological characterization: a habitat mapping study. User's guide to the habitat maps. US Fish and Wildlife Service, Office Biological Services. FWS/OBS-78-07.

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Neill, C., Turner, R.E. Backfilling canals to mitigate Wetland dredging in Louisiana coastal marshes. Environmental Management 11, 823–836 (1987). https://doi.org/10.1007/BF01867248

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Key words

  • Backfilling
  • Mitigation
  • Wetlands
  • Louisiana
  • Dredging