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John ReimerDane County Land & Water Resources
Wisconsin Lakes Partnership Convention
April 10, 2019
for the Yahara River Chain of Lakes (RCL)Improving Flood Resiliency
Lake
Waubesa
Lake
Kegonsa
Lake
Monona
Lake
Mendota
Floodplain
Flood ImpactsStreet
Hydrology of the Yahara Lakes
Rain
RunoffInfiltration
Mendota
Monona
Waubesa
Kegonsa
Urban Development
197019932003201841,000 Acres75,000 Acres
In 2018 there is 2 times more area of development than 1970
Hydrology of the Yahara LakesRain
RunoffInfiltration
Mendota
Monona
Waubesa
Kegonsa
of the Yahara Lakes
RunoffInfiltration
Hydrology
Mendota
Monona
Waubesa
Kegonsa
of the Yahara Lakes
RunoffInfiltration
Hydrology
Hydraulics
Mendota
Monona
Waubesa
Kegonsa
Flow
Aquatic Plants
Friction Flow
Sediment Accumulation
Area Flow
Flow ~ fun(Area, Slope, 1/n, )
Constriction Points
Slope Flow
Exchange Street
1981
2005~2 ft
Recent Lake Levels and FlowsW
ate
r Le
vel
(ft,
NG
VD
29
)
Flo
w(c
fs)
2011 2018Precipitation 50”30”
845.75(7 inches > 100 year)
848.52(10 inches > 100 year)
847.86(10 inches > 100 year)
Mendota
Monona
Waubesa
Kegonsa
Integrated Observations & ModelsFlow Gage
Lake Level Gage
Hydrology
Mendota
Monona
Waubesa
Kegonsa
Integrated Observations & ModelsFlow Gage
Lake Level Gage
Kegonsa
Waubesa
Monona
Mendota
Lake-RiverModel
Integrated Nowcast/Forecast Operation System
for Yahara Waters
Integrated Nowcast/Forecast Operation System
for Yahara Waters
Observations ModelsIntegration
www.infosyahara.org
USGS GaugesWireless Buoys
AOSSINFOS GaugesWeb Cam
Hydrology (Runoff)Hydraulics (River/Lake)
Loss
Mendota
Monona
Waubesa
Kegonsa
Bu
ildin
g R
isk
(USD
Th
ou
san
ds)
Return Period
10 Day, 250 RP
10 Day, 10 RP
$
Reimer and Wu, 2016Flood RiskScenarios
Are we prepared for tomorrow’s flood?
Flood Forecasts
June 16-23, 2014
Past Rainfall
Forecast Rainfall
Watershed0 5 10 15 20 25
0
100
200
300
400
500
600
700
Time (hr)
Dis
ch
arg
e (
cfs
)
Starkweather Creek Unit Hydrograph
Lake-River
Integrated Models
www.infosyahara.org
Flood
Lake Mendota
Lake Monona
Lake Waubesa
Lake Kegonsa
Warning
Science Driven Lake Level Management
• Characterize Flood RiskBuilding
Mendota 500 Year
Monona 500
Waubesa 500
Kegonsa 500
Building
250
10
250
Mixed
LOSS RISKCOMMER Procedure
• Develop Flood Forecast and Warning
Vulnerability Mitigation
Preparedness
New Development:Improve Flood Resiliency
➢ Reduce the Number of Flood Disasters
➢ If Flood Disaster, Recover Quickly Approach
Technical Work Group Policy Task Force
Feb 1, 2019 Mar 18, 2019
Scenarios
Adaptation
Mitigation
a. Lower Lake Mendota one foot (flood storage or maintain lower)
b. Safely Manage Lake Mendota at 100 year water level
c. Remove all dams from the Yahara Lakes
a. Bridge Modificationsb. Yahara River Dredgingc. Flow Reroute and Pumpingd. Combined (b) and (c)
https://lwrd.countyofdane.com/Yahara-Chain-of-Lakes-Lake-Levels-Task-Force
Adaptation – Lower Lake Mendota
Flood Storage or Maintain Lower
-2”
-2”
-2”
-0.5”
Mitigation – Yahara River Dredging
-12”
-11”
-6”
-7”
Cross Section
847.2
846.0
Thank You
TechnicalWork Group
Flood Forecast
PolicyTask Force
Flood Risk
Vulnerability Mitigation
Preparedness
Flood Resiliency