threat to benthic communities and the food web. Once the
oil enters the benthic regime, bottom sediments, and
wetlands habitats, it is extremely difficult to remove and
prevent ecosystem damage. It is not unusual for heavy
oil pollution to impact benthic habitats and organisms
for a decade or more. Microbes (bacteria, in particular,
and fungi) are the primary biotic agents responsible for
degrading oil in aquatic environments (Das and Chandran,
2011; Kostka et al., 2011). The rate of biodegradation of
polluting oil depends greatly on the water temperature,
nutrient availability, oxygen levels, and salinity of the
impacted water body.
Conclusions
Oil pollution is both a potentially acute and insidious
problem in estuarine waters around the world. While there
is great fear of major oil spills that directly impact these
waters, chronic oil pollution can cause serious insidious
adverse effects on biotic communities and habitats. Estuarine benthic, littoral, and wetlands communities and habitats are especially vulnerable and can be altered for
decades by oil pollution.
Bibliography
Clark, R. B., 1992. Marine Pollution. Oxford: Clarendon Press.
Cormack, D., 2010. Response to Marine Oil Pollution: Review and
Assessment. Amsterdam: Springer.
Das, N., and Chandran, P., 2011. Microbial degradation of petroleum hydrocarbon contaminants: an overview. Biotechnology
Research International, 13 pp. http://dx.doi.org/10.4061/2011/
941810.
Doerffer, J. W., 1992. Oil Response in the Marine Environment.
Oxford: Pergamon Press.
Kennish, M. J., 1992. Ecology of Estuaries: Anthropogenic Effects.
Boca Raton, FL: CRC Press.
Kennish, M. J. (ed.), 1997. Practical Handbook of Estuarine and
Marine Pollution. Boca Raton, FL: CRC Press.
Kennish, M. J. (ed.), 2001. Practical Handbook Marine Science,
3rd edn. Boca Raton, FL: CRC Press.
Kim, M., Yim, U. H., Hong, S. H., Jung, J.-H., Choi, H.-W., An, J.,
Won, J., and Shim, W. J., 2010. Hebei Spirit oil spill monitored
on site by fluorometric detection of residual oil in coastal waters
off Taean, Korea. Marine Pollution Bulletin, 60, 383–389.
Kostka, J. E., Prakash, O., Overholt, W. A., Green, S. J., Freyer, G.,
Canion, A., Delgardio, J., Norton, N., Hazen, T. C., and Huettel.,
2011. Hydrocarbon-degrading bacteria and the bacterial
community response in Gulf of Mexico beach sands impacted
by the Deepwater Horizon oil spill. Applied and Environmental
Microbiology, 77, 7962–7974.
Cross-references
Anthropogenic Impacts
Ecological Monitoring
Microbial Degradation
Nonpoint Source Pollution
Oil Pollution
Polycyclic Aromatic Hydrocarbons
OVERWASH
Harry Williams
Department of Geography, University of North Texas,
Denton, TX, USA
Definition
Overwash is the flow of water and sediment over the crest
of a beach system when the run-up level of waves or the
water level, often enhanced by storm surge, exceeds the
local beach or dune crest height (Donnelly, 2008).
Description
Overwash commonly results from hurricane storm surges,
although any storm that raises water levels sufficiently to
overtop the berm crest or dune crest of a beach system
can cause overwash. Depending on the relative height of
water levels and the beach system, two levels of overwash
may be defined: (1) overwash regime, where water levels
are sufficient to overtop low spots in the berm crest or
dune crest, and (2) inundation regime, where water levels
completely overtop the beach and/or dunes and the entire
beach system becomes subaqueous (Sallenger, 2000).
Overwash can significantly impact the geomorphology
of beach systems by eroding the nearshore zone, beach,
and dunes and by creating sediment deposits – known as
washover – landward of the beach system. Under
overwash regime conditions, the flow of water and sediment is funneled through low spots in the berm or dune
crest and deposits isolated, lobate-shaped washover fans
in the backshore area, typically extending tens to hundreds
of meters inland. If overwash occurs along a longer section of a beach system, washover deposits coalesce into
a continuous sediment apron known as a washover terrace.
Under inundation regime conditions, washover sediments
may extend several kilometers inland, forming large
sheetlike deposits in the backshore area. Because
overwash of a barrier island causes a net onshore transfer
of sediment, it may contribute to the gradual landward
migration of the island – a process known as “rollover”
(Orford and Carter, 1982).
Bibliography
Donnelly, C., 2008. Coastal Overwash: Processes and Modelling.
PhD thesis, Sweden, Lund University. Report LUTVDG/
(TVVR-1043).
Orford, J. D., and Carter, R. W. G., 1982. Crestal overtop and
washover sedimentation on a fringing sandy gravel barrier coast,
Carnsore Point, Southeast Ireland. Journal of Sedimentary
Petrolology, 52, 265–278.
Sallenger, A., 2000. Storm impact scale for barrier islands. Journal
of Coastal Research, 16, 890–895.
Cross-references
Washovers
Washover Fans
468
OVERWASH
oil enters the benthic regime, bottom sediments, and
wetlands habitats, it is extremely difficult to remove and
prevent ecosystem damage. It is not unusual for heavy
oil pollution to impact benthic habitats and organisms
for a decade or more. Microbes (bacteria, in particular,
and fungi) are the primary biotic agents responsible for
degrading oil in aquatic environments (Das and Chandran,
2011; Kostka et al., 2011). The rate of biodegradation of
polluting oil depends greatly on the water temperature,
nutrient availability, oxygen levels, and salinity of the
impacted water body.
Conclusions
Oil pollution is both a potentially acute and insidious
problem in estuarine waters around the world. While there
is great fear of major oil spills that directly impact these
waters, chronic oil pollution can cause serious insidious
adverse effects on biotic communities and habitats. Estuarine benthic, littoral, and wetlands communities and habitats are especially vulnerable and can be altered for
decades by oil pollution.
Bibliography
Clark, R. B., 1992. Marine Pollution. Oxford: Clarendon Press.
Cormack, D., 2010. Response to Marine Oil Pollution: Review and
Assessment. Amsterdam: Springer.
Das, N., and Chandran, P., 2011. Microbial degradation of petroleum hydrocarbon contaminants: an overview. Biotechnology
Research International, 13 pp. http://dx.doi.org/10.4061/2011/
941810.
Doerffer, J. W., 1992. Oil Response in the Marine Environment.
Oxford: Pergamon Press.
Kennish, M. J., 1992. Ecology of Estuaries: Anthropogenic Effects.
Boca Raton, FL: CRC Press.
Kennish, M. J. (ed.), 1997. Practical Handbook of Estuarine and
Marine Pollution. Boca Raton, FL: CRC Press.
Kennish, M. J. (ed.), 2001. Practical Handbook Marine Science,
3rd edn. Boca Raton, FL: CRC Press.
Kim, M., Yim, U. H., Hong, S. H., Jung, J.-H., Choi, H.-W., An, J.,
Won, J., and Shim, W. J., 2010. Hebei Spirit oil spill monitored
on site by fluorometric detection of residual oil in coastal waters
off Taean, Korea. Marine Pollution Bulletin, 60, 383–389.
Kostka, J. E., Prakash, O., Overholt, W. A., Green, S. J., Freyer, G.,
Canion, A., Delgardio, J., Norton, N., Hazen, T. C., and Huettel.,
2011. Hydrocarbon-degrading bacteria and the bacterial
community response in Gulf of Mexico beach sands impacted
by the Deepwater Horizon oil spill. Applied and Environmental
Microbiology, 77, 7962–7974.
Cross-references
Anthropogenic Impacts
Ecological Monitoring
Microbial Degradation
Nonpoint Source Pollution
Oil Pollution
Polycyclic Aromatic Hydrocarbons
OVERWASH
Harry Williams
Department of Geography, University of North Texas,
Denton, TX, USA
Definition
Overwash is the flow of water and sediment over the crest
of a beach system when the run-up level of waves or the
water level, often enhanced by storm surge, exceeds the
local beach or dune crest height (Donnelly, 2008).
Description
Overwash commonly results from hurricane storm surges,
although any storm that raises water levels sufficiently to
overtop the berm crest or dune crest of a beach system
can cause overwash. Depending on the relative height of
water levels and the beach system, two levels of overwash
may be defined: (1) overwash regime, where water levels
are sufficient to overtop low spots in the berm crest or
dune crest, and (2) inundation regime, where water levels
completely overtop the beach and/or dunes and the entire
beach system becomes subaqueous (Sallenger, 2000).
Overwash can significantly impact the geomorphology
of beach systems by eroding the nearshore zone, beach,
and dunes and by creating sediment deposits – known as
washover – landward of the beach system. Under
overwash regime conditions, the flow of water and sediment is funneled through low spots in the berm or dune
crest and deposits isolated, lobate-shaped washover fans
in the backshore area, typically extending tens to hundreds
of meters inland. If overwash occurs along a longer section of a beach system, washover deposits coalesce into
a continuous sediment apron known as a washover terrace.
Under inundation regime conditions, washover sediments
may extend several kilometers inland, forming large
sheetlike deposits in the backshore area. Because
overwash of a barrier island causes a net onshore transfer
of sediment, it may contribute to the gradual landward
migration of the island – a process known as “rollover”
(Orford and Carter, 1982).
Bibliography
Donnelly, C., 2008. Coastal Overwash: Processes and Modelling.
PhD thesis, Sweden, Lund University. Report LUTVDG/
(TVVR-1043).
Orford, J. D., and Carter, R. W. G., 1982. Crestal overtop and
washover sedimentation on a fringing sandy gravel barrier coast,
Carnsore Point, Southeast Ireland. Journal of Sedimentary
Petrolology, 52, 265–278.
Sallenger, A., 2000. Storm impact scale for barrier islands. Journal
of Coastal Research, 16, 890–895.
Cross-references
Washovers
Washover Fans
468
OVERWASH