On September 24, 2014, the Institute for Catastrophic Loss Reduction held a workshop entitled 'The role of groundwater in flooding' with Cathy Ryan from the University of Calgary. Cathy Ryan is a Professor in Geoscience at the University of Calgary who is trained as a geotechnical engineer and hydrogeologist. She has been researching groundwater/river interaction river-connected alluvial aquifers in the Calgary region for more than a decade. Her interest in the role of groundwater in flooding was sparked after the 2005 Calgary floods when anecdotal information collected in a door-to-door survey of residents in neighbourhoods around Calgary's Elbow River suggested groundwater inundation (as opposed to overland flooding) caused a significant amount of the economic damage to homes. It is Dr. Ryan's view that groundwater flooding is under-recognized but can be easily monitored and understood.

1. The Role of Groundwater
in Flooding
Cathy Ryan
Professor, P.Eng., P.Geol.
ICLR, Toronto
September 24, 2014
Geoscience, Faculty of Science

2. • River flooding and prediction
• Flood mapping in Calgary
• Groundwater and monitoring wells
• Groundwater flooding in Calgary
• Summary comments

3. Acknowledgements:
Geoscience, University of Calgary
Dr. Jerry Osborn
Jason Abboud
Wageningen University
Jasper Candel
Adriaan de Bourgraaf
City of Calgary
Jonathan Slaney
Frank Frigo

5. www.ctvnews.ca
4th St. SW

6. www.ctvnews.ca

7. www.windsorstar.com/news/Gallery+stunning+photos+from+flooded+Calgary/9218651/story.html

12. Past Flood Events – Bow @ Calgary

13. 1897, South bank of Bow River

14. 1915, old Center St. Bridge

15. www.rightnow.io/breaking-
news/waterton-abstorm-
waterton-lakes-national-
park_bn_1371688987055.html
1929

16. 1932: Memorial Drive

17. 1932: Sunnyside

18. Alberta Environment, Calgary Floodplain Study, 1983

20. Past Flood Events – Bow @ Calgary

21. • River flooding and prediction
• Flood mapping in Calgary
• Groundwater and monitoring wells
• Groundwater flooding in Calgary
• Summary comments

25. To my knowledge,
no river flooding
maps consider
groundwater

26. Flood maps and….
Groundwater Resources in the Calgary Area (Meyboom, 1961)
www.sustainablecalgary.ca

27. Typical vertical cross-section
Cantafio, 2012

28. Alluvial aquifers
alluvial aquifer bedrock (not very permeable)
glacial
till
• river-deposited, under and beside river
• highly permeable (esp. in upper reaches) ‘lattice-
like’; stream insects found up to 2 km away from river (Ward and Stanford,
1988)
• can be effectively mapped using air photo
interpretation
up to several kilometers wide

29. 1915, old Center St. Bridge

30. Escarpment beside alluvial aquifer

31. Escarpment beside alluvial aquifer
Carrie P.

32. Elbow River
NoseCreek

33. Alberta flood mapping
Flood Hazard Area: The flood hazard area is
typically divided into floodway and flood fringe
zones and may also include areas of overland
flow.
Floodway: The portion of the flood hazard area
where flows are deepest, fastest and most
destructive. The floodway typically includes the
main channel of a stream and a portion of the
adjacent overbank area. New development is
discouraged in the floodway.
Flood Fringe: The portion of the flood hazard
area outside of the floodway. Water in the flood
fringe is generally shallower and flows more
slowly than in the floodway. New development
in the flood fringe may be permitted in some
communities and should be flood proofed.
Overland Flow: Areas of overland flow are part
of the flood hazard area outside of the
floodway, and are typically considered special
areas of the flood fringe.

34. Alberta flood mapping
Groundwater Flood Hazard Area:
Region where basement flooding
by groundwater inundation is likely
to occur.
Flood Hazard Area: The flood hazard area is
typically divided into floodway and flood fringe
zones and may also include areas of overland
flow.
Floodway: The portion of the flood hazard area
where flows are deepest, fastest and most
destructive. The floodway typically includes the
main channel of a stream and a portion of the
adjacent overbank area. New development is
discouraged in the floodway.
Flood Fringe: The portion of the flood hazard
area outside of the floodway. Water in the flood
fringe is generally shallower and flows more
slowly than in the floodway. New development
in the flood fringe may be permitted in some
communities and should be flood proofed.
Overland Flow: Areas of overland flow are part
of the flood hazard area outside of the
floodway, and are typically considered special
areas of the flood fringe.
We need a new Area:

35. Alberta flood mapping

36. Alberta flood mapping

37. • River flooding and prediction
• Flood mapping in Calgary
• Groundwater and monitoring wells
• Groundwater flooding in Calgary
• Summary comments

38. Groundwater is water in the ‘saturated
zone’ under the ground surface

40. 14-40
Individual
drive-point
or drilled
monitoring
wells
Screened
intervals
Well Cluster
Groundwater monitoring wells – tools of the trade

41. Waterlevelinmonitoringwell
Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec
Groundwater level
monitoring

42. What if we had groundwater
monitoring wells in flooded areas?

43. What if we had groundwater
monitoring wells in flooded areas?

44. • River flooding and prediction
• Flood mapping in Calgary
• Groundwater and monitoring wells
• Groundwater flooding in Calgary
• Summary comments

45. Roxboro
Rideau
Downtown Calgary

46. C. Greene, A. Roome-Sandrin, T. Simieritsch, M. Towey

47. Flood 2005 – lessons learned
• Overland flow only accounted for 17% of the total
damage reported by residents
• Underground seepage (not overland flow)
responsible for most of flood damage
• Setback only moderately appropriate for
minimizing damage
• Ground elevation was as predictive of damage as
distance from river/floodway
ENSC502 class, 2006

48. A better approach to regulation?
ENSC502 class, 2006
• Regulate basement depths with respect to river
stage and water table elevation
• consider zoning areas based on basement
elevation above the 1:100 year river stage (and
groundwater level)

49. Flooding in Redwood Meadows (ENSC501 2013)
Redwood
Meadows

50. http://www.redwoodmeadows.ab.ca/rwm-flood-2013/

51. http://www.redwoodmeadows.ab.ca/rwm-flood-2013/

52. ENSC501 Field School II,
2013 co-researchers
N. Chin, A. Chung, L. D'Silva, M. DeCock, D.
Doerksen, R. Donais, T. Fairfield-Bilyk, A. Grant, P.
Jones, S. Karim, A. Kerford, A. Klein, J. Kolodziej, E.
Kordich M. Kovacs, L. Laframboise, G. Lam, B.
Linaker, R. Lorimer, A. Ma, K. McGeary, K. Moreira,
S. Muminovic, T. Paradis, G. Perepelkin, A. Pulwicki,
T. Rajabi, M. Revay, N. Rider, S. Ross, J. Sekhon, A.
Smillie, S. Spaho, K.Stuart, K. Sutcliffe, M. Tang, E.
Timmins, E. Webb, L. Wonneck and N. Taube, H.
Jabusch

53. Provincial flood maps
ENSC501 class, 2014
Townsite of
Redwood Meadows

54. Flooding in RWM homes
0
5
10
15
20
25
Numberofresponses
Characteristics of the water
that entered the house?
Clear
Dark
Odourous
Non-Odourous
Other
ENSC501 class, 2014

55. 0
2
4
6
8
10
12
14
Numberofresponses
Where do you suspect water first entered your
house
Sump pump
Floordrain
Foundation and
cracks
Others
Flooding in RWM homes
ENSC501 class, 2014

56. Flooding in RWM homes
ENSC501 class, 2014

57. Flooding in RWM homes
ENSC501 class, 2014

58. How far back would high groundwater
levels propagate?

59. Jan Feb Mar Apr May June Jul Aug Sept Oct Nov Dec
Simulated propagation of high river stage into alluvial aquifer
1.25 m
0.6 m
Candel et al., unpublished

60. Water level responses in alluvial
aquifer
Role of paleo-channels?

61. Figure 6.15 Groundwater flood risk map of Calgary, including the surface flooding zone which has been calculated
by the City of Calgary. Model 1 is the Camp Gardner model, model 2 is the Sue Higgins Park model.
Groundwater
flooded areas
Groundwater flood risk map of Calgary,
including the surface flooding zone
(provided by the City of Calgary).
Candel et al., unpublished data

62. Role of paleochannels in gw flooding?
Tonina and Buffington, 2009.

63. Ongoing work @ UC
• Door-to-door survey of more than 300
residents affected by 2013 flood
• Environmental geophysics to understand
variations in alluvial aquifer
• Identification and monitoring of
groundwater monitoring wells to calibrate
groundwater model

64. • River flooding and prediction
• Flood mapping in Calgary
• Groundwater and monitoring wells
• Groundwater flooding in Calgary
• Summary comments

65. Differentiating between ‘groundwater
flooding’ and sewage backup?
ICLR, 2009

66. How does groundwater enter homes
most easily?
ICLR, 200

67. What does the scientific literature say?
“Groundwater flooding is poorly
understood, often confused with
surface water flooding, and has not
been widely recognized as a
problem, either in the UK or
internationally.”
Hughes et al., 2011

70. Calgary Grade 2 student
questions to Dr. Jerry Osborn
• Should we have built on the floodplain?
• Should we continue to build on it?
---St. Stephen School
• Should we rebuild places like High River or
should people not live there?
---St. Albert School

71. What could the insurance
industry do to identify
groundwater flooding?
• Strategic groundwater investigation and
water level monitoring
• Validated groundwater modelling
• Consider basement floor elevation with
respect to river stage elevation

72. Conclusions
• gw inundation can
significant
• basement floor
elevation w.r.t river
state is relevant
• can “look like” sewer
back-up
• paleo-channels might
be important
• Field investigation, gw
monitoring wells
needed

73. Thanks for your time and attention!
cryan@ucalgary.ca