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

questions?

map by: Karl Musser

Adam Howardahoward@barr.com952-832-2674