Post on 25-Apr-2018
Basin-wide approach to Souris River floodplain management
Adam Howard, PE, CFM
overview
• the Souris River
• history of flooding and flood mitigation projects
• response to 2011 flood
• basin-wide management tools
Souris River
Souris River
flood mitigation projects have been
constructed in response to past flood events
1970’s
USACE federal
levee project
1957
Boundary Dam
constructed
1994
Rafferty & Alameda
dams constructed
1930’s
Wildlife Refuge
dams constructed
several reservoirs provide flood storage
Boundary, Rafferty and Alameda dams
USGS / photo by: Joel M Galloway USGS / photo by: Joel M Galloway
USGS / photo by: Joel M Galloway
Lake Darling stores water for the J. Clark Salyer
national wildlife refuge and provides flood storage
USGS / photo by: Joel M Galloway
Reservoirs are managed to limit flows through
Minot to the design flood if possible
levee system
designed for
5,000 cfs
spring flooding filled the reservoirs and saturated the
watershed – then it rained… a lot
closed all but two Minot
bridge crossings
displaced over
11,000 people
flooded over
4,300 structures
caused over $1.4B
in damages
~27,000 cfs
bridge closures limited transportation connectivity
FEMA / photo by: Andrea Booher
FEMA / photo by: Andrea Booher
FEMA / photo by: Andrea Booher
local stakeholders are determined to protect their
community from a 2011 magnitude event
FEMA / photo by: Andrea Booher
state and local leaders recognized that the
system needed a basin-wide approach
• State / Region• North Dakota State Water
Commission (NDSWC)• Souris River Joint Water
Resources Board (SJRB)• Saskatchewan Water Security
Agency (WSA)
• Federal• US Army Corps of Engineers
(USACE)• FEMA• US Fish and Wildlife (USFW)
• Local• Minot• Burlington• Velva• Sawyer• Rural landowners
objectives for a basin-wide approach
• reduce flood risk in the Souris River Valley
• understand the watershed as a system
• maintain broad stakeholder support
response to 2011 flood
structural projects in developed areas
reservoir operations rural alternatives assessment
Preliminary Engineering Report establish a
project footprint for developed areas
structural projects in developed areas
rural alternatives assessment
reservoir operations
stakeholder objectives for structural projects
• 3 feet of freeboard above flood of record
• minimize loss of housing
• improve transportation connectivity
• no-adverse impact to base flood profile
levee floodwall projects for developed
areas along the Souris River
Burlington
VelvaSawyer
Minot
Mouse
River
Park
Subdivisions
high flow diversions minimized loss of
housing in Minot
reservoir operations need to balance water
supply needs with flood mitigation
structural projects in developed areas
reservoir operations rural alternatives assessment
review of reservoir operation plans
rural alternatives assessment focused on
frequent flooding of ag lands
structural projects in developed areas
reservoir operations rural alternatives assessment
historic flood analysis evaluated stream
gage records to identify flood sources
2,600 cfs
2,670 cfs
3,200 cfs
2,960 cfs
6,770 cfs
1999 summer flood
March August
rural alternatives assessment for
addressing summer flooding in rural areas
hydrologic & hydraulic modeling tool
development
• HEC-HMS hydrologic model
•ungaged areas in North Dakota
• HEC-RAS unsteady flow hydraulic models
•North Dakota
• Saskatchewan
HEC-HMS model was calibrated to
the historic flood events
prairie potholes can create significant
non-contributing drainage areas
USGS / photo by: Joel M Galloway
HEC-RAS unsteady flow models allow
dynamic routing of flood hydrographs
North Dakota model was
calibrated to flood events
from 2009, 2010, and 2011
Canadian model was calibrated
to the 2011 flood event
application of modeling tools
project impacts
diversion operations
flood forecasting
what’s next?
• design and permitting of structural projects
• Corps is preparing for the next flood fight
• FEMA is preparing Risk MAP products
• negotiations on international agreement for reservoir operations