Editing Bangor, Maine (section)

===Hydrology===
[[File:1992USCGCSwivel.jpg|thumb|[[Icebreaker|Ice breaking]] on the [[Penobscot River]]]]
Bangor is on the banks of the Penobscot River, close enough to the Atlantic Ocean to be influenced by tides. Upstream, the Penobscot River [[drainage basin]] occupies {{convert|8570|sqmi}} in northeastern Maine. Flooding is most often caused by a combination of precipitation and [[snowmelt]]. [[Ice jam]]s can exacerbate high flow conditions and cause acute localized flooding. Conditions favorable for flooding typically occur during the spring months.<ref>{{cite web|title=Maine River Basin Report|url=https://www.maine.gov/dacf/flood/docs/maineriverbasin/maineriverbasinreport_chap3.pdf|access-date=December 19, 2015}}</ref>

In 1807 an ice jam formed below Bangor Village, raising the water 10 to 12 feet (3 to 3.7 m) above the normal highwater mark<ref name=usgs>{{cite journal|last1=Thomson|first1=M|last2=Gannon|first2=W|last3=Thomas|first3=M|last4=Hayes|first4=G|title=Historical Floods in New England|journal=US Geological Survey|year=1964|url=http://pubs.usgs.gov/wsp/1779m/report.pdf|access-date=December 19, 2015}}</ref> and in 1887 the freshet caused the [[Maine Central Railroad Company]] rails between Bangor and [[Vanceboro, Maine|Vanceboro]] to be covered to a depth of several feet.<ref name=usgs/> Bangor's worst ice-jam floods occurred in 1846 and 1902. Both resulted from mid-December [[freshet]]s that cleared the upper river of ice, followed by cold that produced large volumes of [[frazil ice]] or slush which was carried by high flows, forming a major ice jam in the lower river. In March of both years, a dynamic breakup of ice ran into the jam and flooded downtown Bangor. Though no people died and the city recovered quickly, the 1846 and 1902 ice-jam floods were economically devastating, according to the Army Corps analysis. Both floods occurred with multiple dams in place and little to no ice-breaking in the lower river. The [[United States Coast Guard]] began [[icebreaker]] operations on the Penobscot in the 1940s, preventing the formation of frozen ice jams during the winter and providing an unobstructed path for ice-out in the spring.<ref>{{cite web|last1=Schmitt|first1=Catherine|title=Ice-out on the Penobscot|date=April 6, 2015|url=http://www.seagrant.umaine.edu/blog/ice-out|access-date=December 19, 2015}}</ref> Long-term temperature records show a gradual warming since 1894, which may have reduced the ice-jam flood potential at Bangor.

In the [[Groundhog Day gale of 1976]], a [[storm surge]] went up the Penobscot, flooding Bangor for three hours.<ref>{{cite journal |publisher= Maine State Climate Office |journal= The Maine Climate |date= March 2002}}</ref>  At 11:15&nbsp;am, waters began rising on the river and within 15 minutes had risen a total of {{convert|3.7|m|ft|order=flip}}, flooding downtown. About 200 cars were submerged and office workers were stranded until waters receded. There were no reported deaths during this unusual [[flash flood]].<ref>{{cite web |url= http://www.erh.noaa.gov/gyx/bangor_flood.htm |access-date= February 10, 2015 |title= The Great Bangor Storm Surge Flash Flood |publisher= National Weather Service}}</ref>