The 2013 Bow River Basin Flood

Transcription

1 The 2013 Bow River Basin Flood Understanding the Big Picture A Presentation to the Priddis Millarville Residents Association 1

2 Looking West and Wondering If. 2

3 The Flood 3

4 The Response 4

5 The Causes 5

6 The Human Component (Natural Floods versus Economic Floods) 6

7 Setting the Stage N ~15,500 km 2 W E S 7

8 This is a relatively New Landscape Most recent glacial event occurred between 20,000 and 9,000 years Relatively young landscape for soils and vegetation Action of glaciers ground up rock and increased availability of minerals; enhanced plant growth and soil formation 8

9 Remnants of Glacial Headwaters 9

10 The Small Scale Picture 10

11 The Upper Bow River Basin Source: ALCES Online 11

12 The Anatomy of the Bow River Basin Source: ALCES Online 12

13 The Basin and Selected Communities W Banff Canmore Lake Louise S Turner Valley Longview Black Diamond High River Millarville Okotoks Bragg Creek Redwood Meadows Priddis Calgary Chestermere Cochrane Airdrie Crossfield N E 13

14 The Major Plumbing Pipes of the Bow River Basin (including alluvial aquifers) Examples of Alluvial Bow Ghost Jumping Nose Elbow Fish Sheep Highwood Creek Hill River Aquifer Pound Mainstem River Drainage Channels Drainage W S N E 14

15 Inter Annual Variation in Precipitation and Flow AVERAGE YEAR W S N E 15

16 Inter Annual Variation in Precipitation and Flow DRY YEAR W S N E 16

17 Inter Annual Variation in Precipitation and Flow WET YEAR W S N E 17 Redwood Meadows

18 Mean Elevation (m.a.s.l( m.a.s.l) Source: ALCES Online 18

19 Mean Slope Source: ALCES Online 19

20 Mean Annual Temperature Source: ALCES Online 20

21 Mean Annual Precipitation (mm) Source: ALCES Online 21

22 Mean Annual Runoff (mm) Source: ALCES Online 22

23 The Basic Math of Water in the Upper Bow Annual Annual Precipitation with Average Rainfall Events Precipitation (~780 mm) Evapotranspiration (~450 mm) Runoff of Surface Water (~250 mm) Decades 23

24 The Basic Math of Water in the Upper Bow Annual Annual Precipitation but Rain falls in Intense Storms Precipitation (~780 mm) Runoff Evapotranspiration of Surface Water (~450 (~450 mm) mm) Runoff Evapotranspiration of Surface Water (~250 (~250 mm) mm) Year to Year 24

25 Monthly Precipitation and Temperature at Calgary Source: Environment Canada 25

26 Much of the Winter Precipitation Accumulates as Snowpack 26

27 Average Pattern of Snowpack Accumulation and Loss Source: Environment Canada Under Climate Change High Scenarios, Rainfall High Rainfall Events Events Possible Can Occur Earlier in the Spring 27

28 How s s the Snowpack this year? Source: Alberta Environment, AESRD 2013 Snowpack 2014 Snowpack 28

29 Flow Rates of the 2013 Bow River at Calgary Source: Alberta Environment, AESRD Average Peak of ~200 cms In 2013, peaked at ~1740 cms 29

30 We have been there many times in the past We will be there many times more Source. Various Historical Archives in Alberta 30

31 June 2013 A Very Large and Concentrated Precipitation Event 31

32 Rainfall Intensity and River Volume A Short and Intensive Rainfall Event of a 2 Day Period River Discharge Rate Extended Bout of Rainfall Over a 1 Week Period Time 32

33 A Lot of Rain over a Short Period of Time 33

34 Rain on Snow 34

35 The Steep Elevation Loss of the Elbow River Headwaters. Source: Elbow River Basin ALCES Simulator North South West East 35

36 The Steep Elevation Loss of the Bow Basin Headwaters. Source: Elbow River Basin ALCES Simulator mass x slope (velocity) = energy Calgary Bragg Creek North West South East 36

37 The Steep Elevation Loss of the Elbow River Headwaters. Source: ALCES Online 37

38 The Erosional Power of Floods Source: Calgary Herald 38

39 Some Math behind the Bow River Flood Event Variable Amount Units 39

40 Under the pull of Gravity, much of this precipitation will get to the Mainstem Rivers, and very quickly 40

41 But the mainstem river systems of the Bow River basin only amount to about ¾ of 1% of the landscape. 41

42 The Elbow Dissipating Energy Source: Rick Bodan, Workabove.com 42

43 The Elbow River and Dissipating Energy Source: Rick Bodan, Workabove.com 43

44 Bow River Basin Reservoir Infrastructure Considerable water can be retained but primary historical purpose e has been electricity generation, not flood mitigation Minnewanka 157 M m 3 Spray 199 M m 3 Barrier, 21 M m 3 Ghost 50 M m 3 Name of Reservoir Working Volume of Water m 3 Bearspaw, 6 M m 3 Most topographically suitable sites for reservoirs have already been used Water storage capacity is continually reduced by sedimentation Glenmore 25 M m 3 L. Kananaskis 58 M m 3 U. Kananaskis 93 M m 3 44

45 Contributing Factors to Floods High Precipitation + Concentrated Precipitation + High Snowpack + Low Landscape Resiliency = High Water (Flood) 45

46 Contributing Factors to Flood Disasters High Precipitation + Concentrated Precipitation + High Snowpack + Low Landscape Resiliency + Floodplain and Floodway Infrastructure = High Water (Flood) and Economic Hardship 46

47 Night Time Light Emission Source: Bow River Basin Alces Online 47

48 Footprint Area of the Energy Sector Source: Bow River Basin Alces Online ~90 km 2 48

49 Footprint Area of the Forest Sector Source: Bow River Basin Alces Online ~40 km 2 49

50 Footprint Area of the Road Sector Source: Bow River Basin Alces Online ~250 km 2 50

51 Footprint Area of the Residential Sector Source: Bow River Basin Alces Online ~900 km 2 51

52 Footprint Area of the Agriculture Sector Source: Bow River Basin Alces Online ~2,500 km 2 52

53 Footprint Area of All Land Uses Source: Bow River Basin Alces Online ~3,700 km 2 53

54 Land Use Footprint Intensity Source: Bow River Basin Alces Online Year Footprint km 2 Study Area km 2 = % ,700 km 2 = 24% 15,500 km ,200 km 2 = 34% 15,500 km 2 54

55 Holding Back the Water; Slowing its Speed 55

56 Holding Back the Water; Slowing its Speed Photo Credit: Jenny Earle 56

57 The Role of Wetlands in Flood Mitigation The Source: Mitsch and Gosselink) 57

58 Loss of Wetlands in the East Slopes Pre Industrial

59 We are Losing Natural Wetland Storage 59

60 Time Series of Natural Area in Upper Bow Source: East Slopes ALCES Simulator Pre Industrial

61 Proper Riparian Function Source: Google Earth 61

62 Land Use and Flashy Runoff In comparison to natural ecosystems, roads, settlements, acreages, cutblocks, croplands, pasturelands, and industrial features generally increase the pace (rate) at which precipitation runs off landscapes. 62

63 In Harms Way 63

64 The Rivers of the Bow Basin are trying to release their flood energy into the floodplain by scouring and depositing We are trying to concentrate its energy by containing it within narrow and constrained channels 64

65 Flooding in Canmore 65

66 Flooding in High River Source: 66

67 Holding Back Water Resilient Natural Systems Engineering Solutions Optimal and Cost Effective Flood Mitigation Strategies require both of these approaches to work in concert 67

68 Moving beyond Silos We need an Integrated Resource Management Paradigm Forestry Energy In practice, the watershed is fully integrated Crops Livestock Residential Mining Reservoirs Unfortunately, our watershed management principles are still based on Silos The volume and flow of its water reflects the full suite of natural processes (climate) and landuses Transportation 68

69 Summary Thoughts Precipitation is, by nature, highly variable in time (seasons, years, decades) Floods are a natural, and required, process for all healthy watersheds Climate Change models suggest that variation in precipitation (floods, droughts) will increase in frequency and intensity The resiliency of the Bow River Watershed to absorb and hold meltwater has been impaired by land uses (forestry, agriculture, transportation, residential) Human infrastructure (crops, forestry, residential, transportation) has accelerated the rate of water movement to mainstem rivers We have intentionally constructed many billions of $ of infrastructure in the flood plain of the Bow River Basin mainstem rivers and its tributaries Although engineering solutions play a key role in flood mitigation, longterm and sustainable solutions to flood risk must incorporate a landscape (watershed) level We should be looking for silver buckshot, not a silver bullet. We are all part of both the problem and the solution. 69

70 What Can We Do Now to Mitigate Flood Risk? 1. Where possible, remove high risk infrastructure from the flood plain 2. Stop approving and building new infrastructure in the flood plain 3. Relocate (elevate) valuables and key utilities (furnaces, water heaters, electrical controls) from basements; 4. Restore natural river function and flow 5. Promote the reconstruction of wetlands and riparian function 6. Promote forestry practices (and other land uses) that encourage water retention in the headwater forest ecosystems 7. Require, and support, regional planning initiatives that promote resilient watersheds 70

71 Implications to MD Foothills 71

72 72

73 Cropland in MD Foothills Pre Agriculture 73

74 Cropland in MD Foothills

75 Cropland in MD Foothills

76 Cropland Trajectory in MD Foothills 76

77 Pasture in MD Foothills Pre Agriculture 77

78 Pasture Land in MD Foothills

79 Pasture Land in MD Foothills

80 Pasture Trajectory in MD Foothills 80

81 Human Popn in MD Foothills (pre) 81

82 Human Population in MD Foothills

83 Human Population in MD Foothills

84 Human Popn Trajectory in MD Foothills 84

85 Wetlands in MD Foothills (pre) 85

86 Wetlands in MD Foothills

87 Human Population in MD Foothills

88 Wetland Trajectory in MD Foothills 88

89 89