Photo Credit: Con Desplanque,

Dr. Danika van ProosdijDept. of Geography

Dykelands: Strategic Importance for Climate Change

Adaptation

MCCAP workshop Feb 2013

Outline

Extensive low lying intertidal environments

Dyking history & subsidence

Truro

Moncton

Sackville

Amherst

Wolfville

Windsor

Freshwater flooding

Geographical Setting

• Other areas: Annapolis valley

• predicted relative sea level rise 1.2 – 1.93 m by 2100 (includes increase in tidal amplitude) (Greenberg et al., 2012; Daigle 2011)

• Increased frequency & intensity of storm activity

Consequences of Climate Change

• damage to coastal infrastructure

• increased property loss

• increased flood risks & potential loss of life

• coastal erosion

• freshwater flooding & dam failure

Greenburg et al., 2012• RSLR~0.41 – 0.79 m by 2055 • Risk of storm surge is therefore predicted to increase

Storm Surge• impact depends on tide level

• water level determines duration

• cause floods & are destructive

• SLR will increase storm surge effects

• dykes have either overtopped or breached on numerous occasions

Strategic Importance for Climate Change Adaptation

Source: Webster et al., 2011

• Dykes are the second line of defense after coastal wetlands & no longer simply protect agricultural land

• Over time residential, public and commercial development has taken place on adjacent lands which are now vulnerable to dyke overtopping or breaching.

• Perceived perception of safety

• It is estimated that temporary delays caused by flooding on the TransCanada Hwy between NS and NB will halt more than $50M/day of trade (Webster et al. 2012).

Factors Affecting VulnerabilitySubsidence & isolation from coastal sediment input

• Isolated from tidal flow and new sediment input, the agricultural soils behind the dyke will compact and subside over time.

• Foreshore marsh however continues to receive sediment & increases in elevation

• Results in significant difference in elevation in front & behind dyke

• Net effect = ponding of salt or freshwater flooding & potential blockage (siltation) of aboiteaux structures

• one way • cannot open at high tide• delay FW drainage

Aboiteaux

Truro, NS, March 31, 2003(Photo Claude Barbeau; http://www.novaweather.net/Flood_2003.html)