Snow melts from heavy snows and rain from slow moving thunderstorms can cause localized flooding which can impact property and infrastructure such as roads. Often this flooding is not related to structures being located in flood plains but a result of storm water management or limited capacity of the soil to absorb water due to frost in the ground in early spring resulting in flooded basements.

Flooding in St. Louis County is usually a result of small-scale flash floods resulting from slow moving thunderstorms and during the spring as a result of snowmelt and ice dams aggravated by increased surface run-off due to frost in the ground which does not allow the soil to absorb moisture.  A third is a type is flooding which results from poor infrastructure (e.g., inadequate sewer and storm water management systems such as ditches and culverts).  Finally, rising lake levels can cause flooding. This type of flooding is caused by a long-term, above average precipitation trend in landlocked basins with a poor lake outlet.  This type of flooding occurs over a period of months or years and is not caused by a single event.

The following is an overview of flooding events for the Duluth area:

• A strong storm system in the summer of 1996 resulted in $300,000 of damages in the Duluth area, primarily on road infrastructure.
• The winter of 2002-2003 resulted in localized flooding due to the lack of snow cover and continuous freezing of water in and outside the channels of the local streams around Duluth. The most serious over bank flooding and ice buildup occurred on the University of Minnesota-Duluth campus along the West Branch of the Tischer Creek. Property management staff had to place sandbags and take actions to keep water and ice from the dormitory adjacent to Griggs Field. Other problems related to the lack of snow cover and great frost depth occurred in all parts of Duluth.  There were also many failed individual septic systems and water line breaks as well as frozen water lines in many locations.
• The area of Fond Du Lac in West Duluth along Water Street is often under water in some locations every spring due to normal spring flows in the St. Louis River. Records indicate that the duration for flooding can last several days due to rising waters of the St. Louis River and Mission Creek. The installation of new sewer and water lines in the area will only encourage investment in property. Although damages appear to be low, the development along Water Street is in the floodway and needs to be tracked and monitored. Future losses could be high if property improvements continue.
• The City of Duluth and neighboring areas suffered damages as a result of the July 4th, 1999 super storm.  Over 10-inches of rain fell in some areas resulting in large damages to roads, culverts, and property. The storm resulted in $800,000 dollars in damages to roads alone.
• There is spotty flooding each spring in Duluth where culverts need to be unplugged and storm sewers need to be replaced.
• The North Shore of Lake Superior and Minnesota Point have been periodically damaged due to high lake levels and storm generated waves from Nor’easters. The damages are mostly due to loss of shore land from erosion, but unexpected high lake levels and storm events could cause damage to public infrastructure and private property along the entire shoreline along Lake Superior.  An example is the extensive damage that was done to parts of the Lakewalk and the Scenic Railroad as a result of high waves during a Nor’easter storm in November of 2001.
• An ice storm in 2001 resulted in damages in the Lincoln Park neighborhood of Duluth.
• Flood damages in the urban area are generally from storm water runoff.  Flood damages include flooding of residences, businesses, industries, transportation facilities, utilities, water supply and sanitary systems, and storm water conduits in Duluth, Hermantown, and Proctor. Expansion of development will likely be the cause for localized flooding problems where none currently exist. Areas of Hermantown and Duluth continue to expand, especially in the Miller Creek Watershed. Loss of wetlands and natural infiltration will likely result in an increase in the rate of storm water runoff rate and volume unless mitigated.
• The City of Cook lies in a low area close to the Littlefork River. In December 2001, FEMA prepared a new floodplain map for the City of Cook. The new map in effect lowers the level of the flood plain within the city limits.  The effect the new mapping will reduce the amount of fill needed for anyone planning to build a new home or place of business to satisfy insurance and building permit requirements.  The previous mapping the City of Cook relied on was from the early 1970s. The current floodplain boundaries are different from the ones shown on the older maps.
  Older houses within the boundaries of the floodplain within the City of Cook will not be required to do anything to those properties. Any new construction will need certification from an engineer or surveyor that the first floor of the structure is at a minimum elevation. This will help offset potential damages from floods.

Areas of St. Louis County outside of the Duluth area that experience flooding are primarily in the cities of Cook, Hibbing, Floodwood, Virginia, Mountain Iron, Chisholm, Eveleth and the Town of Cotton. Lake flooding occurs along the shores of Lake Kabatogama and lake Esquagamah.  In addition to these communities, other areas experienced flooding after mega-storms such as the July 4th, 1999 event. Most of these floods are directly related to an excessive amount of rainfall over a short period of time. Further, rain events that occur during spring melt combined with frozen soils that prevents infiltration exacerbate flooding.  

• Flooding as a result of beaver dams is a concern in some of the rural areas.
• A number of flooded areas are not mapped as floodplains on Flood Insurance Rate Maps from FEMA. Storm water and runoff are the primary source of flooding waters in these areas.  
• The City of Floodwood has some of its city proper within the mapped floodplain. The Floodwood River enters the St. Louis River on the east side of the city. Just downstream the Savannah River enters the St. Louis River. Ice jams at the confluences contribute to flooding events at times. Floodwood and areas along these rivers outside of the city have flooded many times in the past 10-years.  In 1997, an estimated 10 to 20 homes and businesses flooded resulting in $160,000 in damages.
• City of Hibbing: Most of the flooding in this city proper is not within mapped floodplain. Runoff and storm water management systems have caused flooding. The City of Hibbing has done a number of sewer rehabilitation projects since the mid-1970s dealing with storm water and wastewater upgrades.  Since 1977, Hibbing has done a total of 12 sewer rehabilitation projects totaling $4,981,244 dollars.
• In 1999, the City of Hibbing received $512,307 dollars from a combination of Federal, State, and local match dollars for city street, bridge, treatment plant, and debris removal projects.
• The City of Hibbing submitted FEMA flood claims on August 20th, 1980, August 13th, 1988, July 6th, 1989, June 16th, 1994, July 4th – 5th, 1999, and June 22nd, 2002. The total amounts of these claims are listed below.  Totals from these claims exceeded $2,252,000 dollars.
• Cities of Virginia and Mountain Iron: Most of the flooding in these two cities is not within mapped floodplain. Mostly runoff and storm water management systems have caused flooding.  They have been making improvements, in part, funded by Federal Disaster Relief grants.
• The City of Mountain Iron had back-to-back 100-year floods in 1994 and
   1995 where there were a number of road washouts, but no structural
   losses. Mountain Iron began receiving FEMA funds in 2000 to widen out
   the Silver Creek area. This project is just wrapping up as of the publishing
   of this plan.
• The City of Virginia has historically had flooding problems in the ballpark
   area adjacent to Trunk Highway (TH) 53.  The cities of Mountain Iron and
   Virginia worked on a joint proposal to secure funding to alleviate flooding
   within city limits.
• City of Chisholm: Most of the flooding in this city proper is not within
   mapped floodplain. Mostly runoff and storm water management systems
   have caused flooding.
• Shoreline properties along the Whiteface River in Cotton Township, Lake
   Esquagamah, Lake Kabetogama, and St. Louis River have been flooded. 
   The elevation of Q100 has been determined for Lake Esquagamah and the
   other lakes that are “ponded” portions of Embarrass River. The
   floodplain maps for the Whiteface River and St. Louis River, outside of
   Floodwood and Cloquet, are based on the initial flood hazard boundary
   maps and no Q100 elevations have been determined.
• Flooding has not typically been a problem in the City of Orr, however,
   there are some flooding problems in Leiding Township and the Crane
   Lake and Ash Lake areas.