Waters Overflow Banks of Fox — Flood Advisory Through Monday
CREDIT: National Weather Service Screenshot. Click on the map to visit the web page and interactive map.
The recent rains have caused rises along the Fox River, overflowing the banks in some spots and spurring the National Weather Service in Chicago to issue a Flood Advisory for the Fox River at the Algonquin Tailwater.
The advisory affects Kane and McHenry counties and offers precautionary advice not only for homeowners and businesses at the river’s edge but for motorists, who should be on the lookout for road flooding.
“If you encounter a flooded road, turn around and find an alternate route,” the Flood Advisory says.
Flood forecasts for Algonquin were moved to a new location in 2011. As of 8:30 a.m. Wednesday (Dec. 16, 2015), the stage was 8.6 feet. The action stage is 9.0 feet and flood stage is 9.5 feet.
According to the NWS’s “High Water Terminology” page, the action stage is reached when a rising stream or river “needs to take some type of mitigation action in preparation for possible significant hydrologic activity. The type of action taken varies for each location, but data should be closely monitored by any affected people if the stage is above action stage.
In general, a flood stage is the water level, as read by a stream gauge or tide gauge, for a body of water at a particular location, measured from the level at which a body of water threatens lives, property, commerce or travel.
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National Weather Service Terminology
SOURCE: National Weather Service website
Bankfull Stage — an established gage height at a given location along a river or stream, above which a rise in water surface will cause the river or stream to overflow the lowest natural stream bank somewhere in the corresponding reach. The term lowest bank is however, not intended to apply to an unusually low place or a break in the natural bank through which the water inundates a small area. Bankfull stages on streams with natural or manmade high banks can be defined by the predominant vegetation line on the banks. The bankfull stage on many streams is associated with the 2-year recurrence interval flood. Bankfull stage is not necessarily the same as flood stage.
Action Stage — the stage which, when reached by a rising stream, represents the level where the NWS or a partner/user needs to take some type of mitigation action in preparation for possible significant hydrologic activity. The type of action taken varies for each gage location. Gage data should be closely monitored by any affected people if the stage is above action stage.
Flood Stage — an established gage height for a given location above which a rise in water surface level begins to create a hazard to lives, property, or commerce. The issuance of flood advisories or warnings is linked to flood stage. Not necessarily the same as bankfull stage.
Flood categories are terms defined for each gage location that describe or categorize the observed or expected severity of flood impacts in the corresponding stream segment or nearby stream. The severity of flooding at a given stage is not necessarily the same at all locations along a stream due to varying channel/bank characteristics on portions of the stream. Therefore, the stage for a given flood category is usually associated with lowest water level corresponding to the most significant flood impacts somewhere in the reach. The flood categories used in the NWS are minor, moderate, and major flooding, but all three of the flood categories do not necessarily exist for each gage location. Most commonly, gages in remote areas may not have a major flood stage assigned. Record flooding is flooding that equals or exceeds the highest stage or discharge at a given site during the period of record keeping.
Minor Flooding is defined to have minimal or no property damage, but possibly some public threat. A Flood Advisory product is issued to advise the public of flood events that are expected not to exceed the minor flood category. Examples of conditions that would be considered minor flooding include:
- water over banks and in yards
- no building flooded, but some water may be under buildings built on stilts (elevated)
- personal property in low lying areas needs to be moved or it will get wet
- water overtopping roads, but not very deep or fast flowing
- water in campgrounds or on bike paths
- inconvenience or nuisance flooding
- small part of the airstrip flooded, and aircraft can still land
- one or two homes in the lowest parts of town may be cut off or get a little water in the crawl spaces or homes themselves if they are not elevated
In remote areas with few specific impacts, floods with 5-10 year recurrence interval would be assumed to be causing minor flooding on streams in the area.
Moderate Flooding is defined to have some inundation of structures and roads near the stream. Some evacuations of people and/or transfer of property to higher elevations may be necessary. A Flood Warning is issued if moderate flooding is expected during the event. Examples of conditions that would be considered moderate flooding include:
- several buildings flooded with minor or moderate damage
- various types of infrastructure rendered temporarily useless (i.e. fuel tanks cannot be reached due to high water, roads flooded that have no alternates, generator station flooded)
- elders and those living in the lowest parts of the village are evacuated to higher ground
- access to the airstrip is cut off or requires a boat
- water over the road is deep enough to make driving unsafe
- gravel roads likely eroded due to current moving over them
- widespread flooding, but not deep enough to float ice chunks through town
- water deep enough to make life difficult, normal life is disrupted and some hardship is endured
- airstrip closed
- travel is most likely restricted to boats
In remote areas with few specific impacts, floods with 15-40 year recurrence interval would be assumed to be causing moderate flooding on streams in the area.
Major Flooding is defined to have extensive inundation of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations are necessary. A Flood Warning is issued if major flooding is expected during the event. Examples of conditions that would be considered major flooding include:
- many buildings flooded, some with substantial damage or destruction
- infrastructure destroyed or rendered useless for an extended period of time
- multiple homes are flooded or moved off foundations
- everyone in threatened area is asked to evacuate
- National Guard units assist in evacuation efforts
- erosion problems are extreme
- the airstrip, fuel tanks, and the generator station are likely flooded
- loss of transportation access, communication, power and/or fuel spills are likely
- fuel tanks may float and spill and possibly float downstream
- ice chunks floating though town that could cause structural damage
- high damage estimates and high degree of danger to residents
In remote areas with few specific impacts, floods with 50-100 year recurrence interval would be assumed to be causing major flooding on streams in the area.
For more information
You can email the National Weather Service by clicking the following links:
- Submit a report of flooding or flood impact conditions
- Submit a comment or question about these terms
Flood Advisory
FLOOD ADVISORY NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 914 AM CST WED DEC 16 2015 ...The National Weather Service in Chicago has issued a Flood Advisory for the Fox River... Fox River at Algonquin Tailwater affecting Kane and McHenry Counties .Recent heavy rains have caused rises along the Fox River. PRECAUTIONARY/PREPAREDNESS ACTIONS... Safety message...If you encounter a flooded roadway...turn around and find an alternate route. Additional information can be found at weather.gov/chicago. && ILC089-111-170314- /O.NEW.KLOT.FL.Y.0144.151216T1514Z-151221T1500Z/ /AFBI2.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ 914 AM CST WED DEC 16 2015 The National Weather Service in Chicago has issued a * Flood Advisory for The Fox River at Algonquin Tailwater. * until Monday morning. * At 830 AM Wednesday the stage was 8.6 feet. * Action stage is 9.0 feet. * Flood stage is 9.5 feet. * Recent activity...Flood forecasts for Algonquin were moved to this location on July 5 2011. Gage zero datum is different from the old gage location. Flood and action stages have changed. * Forecast...The river will rise to near 9.0 feet by Friday afternoon.
