The City of Ottawa Flood Hazards
The City of Ottawa, located in North Central LaSalle County,
approximately 45 miles West of Joliet and 90 miles South of Rockford.
The primary water course and sources of flooding are the Fox River and
the Illinois River. A secondary and relatively inconsequential source
of flooding is from the Goose Creek watershed which is only 6.58 square
miles. The total fall for the Fox River from its source to Ottawa is
471 feet. The Fox River flows Southwest from its source, just North of
Waukesha, Wisconsin, 187 miles to the mouth at the Illinois River in
downtown Ottawa. There is a total of 2657 square miles of watershed in
this basin. The water level of the Fox River is influenced more by the
rainfall and runoff of Northeastern Illinois and Southern Wisconsin than
by local rain events.
The Illinois River is influenced by Northeast Illinois, and
Northwestern Indiana. The Kankakee, Iroquois, Des Plaines and Chicago
Rivers are tributaries of the Illinois River upstream of Ottawa. A
critical component of our flood hazard in Ottawa is that the watershed
of the Fox and Illinois Rivers upstream of Ottawa is more than 11,000
square miles. As a result, the City could receive a minimal
amount of rain, yet experience a severe flood event caused by runoff
from the watershed.
The Illinois River flows West from its source at the confluence of
the Kankakee and Des Plaines Rivers, through Ottawa from (mile mark
242.6) the Eastern boundaries to the Western city limits (mile mark
Flood discharges during a 100-year flood event for the Goose Creek is
1,700 cubic feet per second (cfs), for the Fox River is 42,600 cfs and
for the Illinois is 114,000 cfs.
The Illinois and Fox River flood characteristics have been studied by
the Rock Island, U.S. Army Corps of Engineers. A Flood Damage
Reduction Project for the Illinois and Fox Rivers was completed by the
USACE in February 2001. A levee was constructed by the USACE pursuant to
this study on the Illinois and Fox Rivers. This levee lost its
accreditation in March of 2010. The preliminary Digital Flood Insurance
Rate Maps, published in March 2010, increased the Base Flood Elevation
on the Illinois and Fox Rivers approximately 1.5 feet. The levee
provides protection for Ottawa High School, considered a critical
facility, and a small section of the Fox River levee does not have the
Flood Protection Elevation required for critical facilities. The Federal
Emergency Management Agency (FEMA) has published a preliminary Flood
Insurance Study dated March 10, 2010. A Hydrologic and Hydraulic
analyses was performed for the City of Ottawa for the Goose Creek in
Record floods have occurred in 1974, 1982, 1983, 1996, 1997, 2007,
2008 and 2009 and 2013. The flood of 2013 crested 1.5’ above any
recorded event. The 1974, 1983, 1996, 2007, 2008 and 2013 floods all
resulted in Federal Disaster declarations. In 2008 Central School was
flooded and subsequently declared substantially damaged. This was
perhaps the largest single flood loss recorded in the City of Ottawa
with FEMA providing over 12 million dollars in relief.
During a flood event Green Street, a secondary means of egress for
the East side of Ottawa, becomes impassible. The only other access to
the East side is the Main Street bridge. During record flood events
this bridge could become unusable, effectively isolating the East side.
This happened during the 2013 flood event. Fire and police personal
were staged, with apparatus, on the south side of the bridge with a
helicopter on stand-by in the event a medivac was needed.
During record flood events residential flooding occurs on the East
side (Illinois River) and an area known as the “Flats” (Fox River) at
approximately cross section “D” as noted on FIRM panel #530 dated July
18, 2011. As of this date all the homes in the Special Flood Hazard
Area (SFHA) of the Flats have been purchased and removed. During these
events OSF St. Elizabeth hospital can be threatened, however, they have
recently constructed a flood protection wall which protects above the
500-year event. Ottawa High School is also threatened. The high school
has a very good flood fighting plan which has been extremely effective,
even preventing damage from the record floods of 2008 and 2013. OSF
St. Elizabeth hospital also has a very effective flood fighting plan
that was recognized by Witt O’Brian Associates during a 2014 evaluation.
The City of Ottawa’s Waste Water Treatment Facility can also be
threatened. A flood protection wall is being constructed at this time.
The YMCA is the only other commercial facility affected during major
flood events. Their flood fighting plan prevented major losses during
the 2013 event.
During the winter months ice jams on the Fox River cause localized
flooding from the mouth upstream to the OSF St. Elizabeth hospital.
Flood Threat Recognition System
LEADS: Law Enforcement Agency Data System: A
nationwide system utilized by all Law Enforcement Agency’s to receive
and transmit data. The City of Ottawa’s Emergency 911 Communications
Center receives emergency weather notification calls from the Emergency
Weather Service across the LEADS. This system is used to make emergency
weather notification calls. This system is manned at all time and
provides, storm, flooding and other weather-related data and alerts.
EmNet: Emergency Management Network: This is a
satellite based system. The EmNet server is constantly transmitting
data stream that is derived from computers located at the National
Oceanic and Atmospheric Administration (NOAA) Port facility. This data
stream includes all warnings and alerts issued by the National Weather
Service (NWS) for stations within the US. This is an audio alarm
program. When an alert is broadcast the alarm notifies on duty
dispatchers. The system is monitored at all times.
NOAA: National Oceanic & Atmospheric Administration:
The Emergency 911 Communications Center monitors the NOAA system at all
times. A NOAA Weather Alert Radio, monitored 24/7, relays weather
alerts to the dispatchers. Dispatchers can check local forecasts,
radar, storm watches and warnings, weather graphs and real-time weather
reports. When emergency notification from either EmNet or LEADS is
transmitted, dispatch uses this network for further details.
National Weather Service web page: The National
Weather Service hosts a website with Advanced Hydrologic Prediction
Service. This site is also monitored at the Emergency 911
Communications Center as well as Community Development Department, Waste
Water Treatment plant and by city personal responsible for floodplain
management. This site gives advanced warning of flood threats on the
Illinois River, with approximately 48 hours lead time. In March 2016,
the National Weather Service with the Illinois State Water Survey
activated flood inundation mapping for the City of Ottawa. These maps
depict flood levels 4 feet in excess of any flood on record.
Additionally, these maps have depth grids for all flooded areas.
U.S. Geological Survey web page: The City of
Ottawa’s floodplain management team subscribes to a real time National
Water Information System. This site provides valuable information
related to water discharge rates immediately upstream of the City
limits. When a flood watch or warning is issued this site is used
primarily for real time data. Prediction of flooding on the Fox River
in Ottawa, from the Fox Lake Pool is generally 24 to 48 in advance. In
March of 2016 the Illinois State Water Survey with the National Weather
Service and The National Oceanic and Atmospheric Administration added
Inundation Maps for the City of Ottawa with depth grids.
Emergency Warning Dissemination
Emergency 911 Communications Center: The Emergency
911 Communications Center, also known as a Public Safety Answering
Point (PSAP) is a facility equipped and staffed to receive emergency and
non-emergency calls requesting police, fire, EMS and other public
safety services via telephone and other communications devices. The
Ottawa Police Department’s Emergency Communications Center is a
“primary” PSAP, which means emergency calls are answered here first and
triaged. The Center is staffed and operating 24 hours a day, 7 days a
week. The PSAP is also the point from which all calls are dispatched.
The Ottawa Police 911 Communications Center employees (also known as
Telecommunicators) are first level public safety communications
professionals who essentially serve as first responders to every class
of emergency for which public safety services are provided. The
Telecommunicators primary responsibility is to receive, process,
transmit and/or dispatch emergency and non-emergency calls for police,
fire, EMS and other public safety services via telephone or other
The Community Emergency Notification System (Nixtle)
is a web-based emergency notification system that will assist public
safety officials in making emergency notifications in a timely manner.
The system allows the originator to initiate a voice message broadcast
to residents or businesses by their predetermined group or geographic
location. This system is used to notify residents in the floodplain and
critical facilities in the community of impending flood events.
Cable TV & Radio Emergency Broadcasts: A system
in place at the Ottawa Police Department for notification of life
threatening emergencies, catastrophic flooding or other community
disasters. The Ottawa police dispatch can interrupt local radio and
cable TV broadcasts with emergency information and directions.
Ottawa Daily Times: When a flood emergency exists,
the City Engineer or Building Official notifies the news center with the
appropriate warning. This can be done via telephone, the web or text
from a cell phone. The news center then publishes the warning on their
front page of the web-based media and broadcasts this warning via their
Social Media Network to Facebook, Twitter and all email subscribers.
Emergency 911 Communications Center will notify the City Engineer and
the Building Official upon any posted flood watch. The City Engineer
and Building Official will begin to monitor the National Weather
Service’s Advanced Hydrological Prediction Service for both the Illinois
and Fox River. City of Ottawa Inundation mapping for the Fox and
Illinois River will be used to gauge the extent of inland flooding with
depth grids. The Building Official will contact the High School for live
In the event the National Weather Service issues a flood warning, the
City Engineer and the Building Official will be immediately notified by
the Emergency 911 Communications Center. After monitoring the Advanced
Hydrological Prediction and determining when the Action Plan will be
implemented, the City Engineer will notify the appropriate department
heads to take action.
River Gauges & Data Collection Points
The river gauge is a pressure transducer with a Data Collection
Platform located at a gatewell in the Ottawa Township High School
levee. The gage elevation was surveyed and certified by the U.S. Army
Corps of Engineers. The data is linked to the Corps of Engineers
Hydraulics Branch and the National Weather Service via satellite.
Ottawa High School also has a secondary gage located in the same
gatewell. This gage is hardwired to the school. Data is collected and
stored by the Ottawa Township High School Maintenance Staff as a backup
to the National Weather Service gage and is calibrated and compared to
the National Weather Service gage.
Ottawa High School also has three staff gages located around the
property with elevation marks established by survey. The City of Ottawa
has a staff gage located on the downstream face of the north pier of
Highway 23 Bridge. This gage has been established by survey and has
been compared and verified to the gage at Ottawa High School by previous
The gage at Ottawa High School is an official forecast point for the
National Weather Service. The National Weather Service has multiple
official forecast points both upstream and downstream of this gage on
both the Illinois and Fox Rivers. This data is monitored at all times
by the City of Ottawa’s Emergency 911 Communications Center.
Upstream indicators on the Illinois allows a 24 to 48-hour warning of peak flows.
Since the Corps of Engineers gauge is an official forecast point for
the National Weather Service, it is continuously monitored. Maintenance
is performed as required, and the Corps has dedicated staff to maintain
these gages and can be dispatched in short notice to make repairs. The
City of Ottawa performs witnessed monthly checks of all data collection
and communications and keeps record of these on file at the dispatch
On the Fox River approximately 5000 feet upstream of Ottawa city
limits is another gauge. This gauge is maintained by the U.S.
Geological Survey, Urbana, Illinois. The upstream gauges are easily
monitored from the National Weather Service website and are an excellent
warning source. Additional information is available on a real-time
basis from the USGS web site. Predictions from the Chain of Lakes pool
levels allow at least a 24-hour warning.
ALL DEPARTMENTS REFER TO APPENDIX B, INUNDATION MAPS OR GO TO:
|Stage||Staff Assignment||Required Action and Notifications|
|459.9|| None||No action normal pool|
|460.5||Scott Clinch, High School||River
infiltration to southeast corner of levee at baseball field. Gatewell D
closed, pumping begins and flood fighting preparations begin. Building
Official contacts Scott Clinch.
|460.6||Public Works||Backup in CSO 009, arch sewer to Webster St. Close sluice gate MH. City Engineer confirms with Public Works Director. (5 min)|
|460.8||High School||Pumping operations start (45 min.)|
|460.8||River Rescue||Emergency boat docks and ramps begin to flood. Building Official Contacts River Rescue. (5 min)|
|461.24||Public Works||Illinois River overtops CSO 18B at High School. City Engineer confirms with Director of Public Works (5 min)|
|461.3||Ottawa High School||River infiltrates Eastside City storm system. Pumping begins to control storm water and mixed systems. (1 hour).|
|461.7||City of Ottawa||Fox
River Tops Combined Sewer Overflow (CSO) 18A at Ottawa High School.
Close valve in Manhole 011C546. City Engineer confirms with Public
Works. (20 min)|
|462.5||Ottawa High School||River flooding infiltrates West Parking Lot. Close Gate B, begin pumping to mitigate seepage & storm water. (45 min)|
|463||City of Ottawa||City
Engineer & Building Official to notify OSF St. Elizabeth Hospital,
YMCA, & Public Works, Ottawa Police and Fire Departments to prepare
for further flood fighting. (30 min).|
|463.5||Ottawa High School||Illinois River flows into effluent pipe. Close gravity effluent valve and start high river pumps. (30 min)|
|463.5||City of Ottawa||Building
Official notifies Public Works to close Allen Park. Have Thrush
Sanitation remove portable toilets from Allen Park and Fox River Park.
Have the electrical inspector see that the River Walk power is shut
down. (See appendix A, River Walk Electrical Shut Down Procedure). (1
hr. 20 min).|
|464||City of Ottawa||City Engineer to notify Ameren and Nicor Gas to close down all utilities in the Special Flood Hazard Area. (5 min)|
|465||Heritage Harbor||Harborwalk floods. Dock ramps cannot be accessed without a boat.|
Moderate Flood Stage
OSF St. Elizabeth Hospital||Building Official contacts hospital. Lower green spaces on the hospital grounds begin to flood. (5 min)|
|465.3||City of Ottawa||City Engineer Contacts Public Works to barricade Hudson Street as it will become impassible (25 min).|
|465.5||Marquette High School||Football fields begin to flood. Building Official contacts high school. (5 min)|
|466||Heritage Harbor||Travel-lift slab area begins to flood. Secure all items and remove to high ground. (2 hours)|
|466.4||City of Ottawa||City
Engineer ensures that River Walk at Hudson Street is closed, Fox River
Park is closed and St. Clair Street is barricaded. (1 hour)|
|467.2||City of Ottawa||Illinois River level reaches Douglas and Leland CSO. City Engineer to notify Waste Water Treatment Plant. (5 min)|
|467.3||City of Ottawa||Illinois River level reaches Chester Street CSO. City Engineer to notify Public Works to close sluice gate MH012DO11 (40 min)|
|467.5||City of Ottawa and Shoreline Boat Club||Building
Official to notify Streets Department to close Green Street. Have the
police activate the NIXLE to notify east side resident. Notify
Shoreline Boat Club to secure boats & land cradles and to evacuate
property. (City 25min, Shoreline 2 hours)|
|468.1||City of Ottawa||Illinois River floods the old Central School property. Blockade driveway entrances. (20 min)|
|468.1||River Rescue||Building is threatened. River Rescue personnel to remove equipment to higher ground and begin 24-hour watch. (2 hours)|
|468.7||City of Ottawa||Fox River is flowing into CS0-011 off Main Street.|
|468.7||River Rescue||River infiltrates building.|
|468.7||City of Ottawa||Illinois River is flowing into CS0-006 off Riverview Drive.|
|468.8||YMCA||Flood fighting begins, sandbag lower level entry ways. (4 hours)|
MAJOR FLOOD STAGE
|469||OSF St. Elizabeth Hospital||Shut storm drain valve off. (15 min)|
|469||City of Ottawa||City
Engineer engages incident command. Activate the City of Ottawa’s
Emergency Response Plan. Notify the Mayor of emergency status.
Designate Public Information Officer and contact LaSalle County EOM,
Contact Red Cross, WCMY radio station, and The Times. Activate
Community Emergency Notification System (NIXLE) Inform entire community
of the current flood threat.|
|470||Ottawa High School||River infiltration at Shabbona Street begins. Construction of sandbag enclosure begins. (4.5 to 6 hours).|
|470.2||City of Ottawa||City Engineer to have Public Works monitor Jackson Street lift station. Shut down power if necessary.|
|471.3||YMCA||Fox River reaches center of parking lot.|
|471.5||City of Ottawa||Fox River is flowing into CS0-013 off Madison Street|
|472||OSF St. Elizabeth Hospital||West parking lot floods|
|472.2||City of Ottawa||Sand bag Waste Water Treatment facility berm (6 hours)|
|473||OSF St. Elizabeth Hospital||Emergency Room Floor Elevation. Flood protection wall installed in 2009 should prevent any infiltration of water.|
|474||Shoreline Boat Club||Building will be under water.|
|474||City of Ottawa||Illinois River will overtop the berm at WWTP if not sandbagged.|
|474.5||Ottawa High School||Top of Fox River levee.|
|475||Heritage Harbor||All power should be shut down to docks. (15 min).|
|475.33||Heritage Harbor||Lowest basement begins to flood|
|475.85||Ottawa High School||Top of flood protection wall on Fox River South of Main Street Bridge.|
|476||City of Ottawa||City
Engineer to monitor Main Street bridge. If the Main Street bridge is to
be closed, move to Unified Command. Consider evacuation of East side.
Mayor to consider Disaster Declaration. Notify all residents of East
Side via NIXLE. Police and Fire Departments stage on south side of
bridge. Have lifeline helicopter on standby (may use high school west
lot). (1 hr.)|
|476.8||Heritage Harbor||Roadway connecting West peninsula to Canal Road begins to flood. Power transformers should be shut down.|
During a flood event at “Flood Stage” and “Moderate Flood Stage” the
impact to the general public is limited. Most repetitive loss
properties that were affected at these stages have been mitigated. The
Police Dispatch does take on additional burden but generally there are
no “call back to duty” during these stages. In the flood response
section of this plan, there are designated times and stages to shut down
utilities such as power and gas.
When the flood stage moves to a “Major” event, additional personal
are called to duty. During the major event of 2013, the mayor declared
an emergency status and called all city personal back to duty. As noted
in the response section the fire and police department stage equipment
and personal on the east side of the Main Street bridge until the flood
After the flood event there is a dedicated packet of hand outs
(outlined in the PPI) that is delivered to all properties affected by
the flood. This informational hand out outlines flood safety measures
during and after a flood event.