Modeling the Effects of Sea-Level Rise on Groundwater Levels … · 2016. 6. 21. · Short title;...

Short title; Author(s), Date

Modeling the Effects of Sea-Level Rise on Groundwater Levels with Implications for

Road Infrastructure in Coastal New Hampshire

Jayne F. Knott, Jo Sias Daniel, Ph.D., Jennifer M.

Jacobs, Ph.D., and Paul Kirshen, Ph.D.

UNH Department of Civil and Environmental

Engineering

“Better Safe Than Sorry” – Workshop June 21, 2016

Short title; Author(s), Date

Climate Change Overview

2

Short title; Author(s), Date

Climate Change in the Northeast Temperature

3

Source: 2014 National Climate Assessment

Short title; Author(s), Date

Climate Change in the Northeast Precipitation

4

Source: 2014 National Climate Assessment

Short title; Author(s), Date

Climate Change in the Northeast Sea-Level Rise

5

Source: 2012 National Climate Assessment

Short title; Author(s), Date

Climate Change in the Northeast Sea-Level Rise

6

Coastal NH – Winter storm 2/8/2016

Short title; Author(s), Date

Motivation for this study

7

Short title; Author(s), Date

Water is a major cause of damage to roads

8

Short title; Author(s), Date

The useful life of the pavement structure decreases with an increase in the percent of time

the structure is saturated.

9

Source: Cedergren, 1988

Short title; Author(s), Date

High moisture content weakens the unbound layers beneath the hot mix asphalt

10

Short title; Author(s), Date

How does water get into pavement systems?

11

Short title; Author(s), Date

What does sea level have to do with groundwater?

12

Source: U.S. Geological Survey

Short title; Author(s), Date

Project Objectives

13

1. Create a NH Seacoast Transportation Climate Working

Group

2. Determine the effects sea-level rise on coastal

groundwater levels

3. Identify roads that may be vulnerable to damage from

rising groundwater

4. Conduct pavement performance evaluations

5. Demonstrate the value of adaptation through case

study

Short title; Author(s), Date

Methods

14

• Identify areas where the groundwater is less than 10-feet

deep using current and historical groundwater observations

• Update the USGS groundwater flow model of the Seacoast

Region of NH (Mack, 2009) using MODFLOW-2005

• Simulate various sea-level rise scenarios to identify areas

where groundwater is predicted to rise

Short title; Author(s), Date

Political Map of Study Area

15

Short title; Author(s), Date

Groundwater Observations

16

Short title; Author(s), Date

Depth to GW from observations (1960-2015)

17

GW table is greater than or equal to 15-ft. below the ground surface.

Observation wells

GW table is very close to the ground surface

Short title; Author(s), Date

Depth to GW in Portsmouth, NH

18

Short title; Author(s), Date

Depth to groundwater near the I-95/Rte. 16 Interchange in Portsmouth, NH

19

Short title; Author(s), Date

Depth to groundwater near Route 101 in

Hampton– Evacuation Rte. From Hampton Beach

20

Route 101 Route 101

Short title; Author(s), Date

Groundwater Model Construction

21

Short title; Author(s), Date

Groundwater Model

22

• Calculates the groundwater flow equation for many small

areas, or cells, within the model domain

• Hydraulic properties of surficial and bedrock geology

• Groundwater recharge

• Streamflow

• Public and private water withdrawals and returns

Short title; Author(s), Date

GW model domain and boundary conditions

23

Short title; Author(s), Date

Model grid is 535 rows and 350 columns, each grid cell is 200’ x 200’

24

Short title; Author(s), Date

Observation wells and CSWs

25

Short title; Author(s), Date

Sea-level rise scenarios

26

Time Period 2050 2100

Intermediate low 0.6 ft. 1.6 ft.

Intermediate high 1.3 ft. 3.9 ft.

Highest 2.0 ft. 6.6 ft.

From: National Climate Assessment (Parris et al., 2012) using

MSL as a reference

Short title; Author(s), Date

Groundwater Modeling - Results

27

Short title; Author(s), Date

Surface water inundation with 6.6 feet of SLR

28

Groundwater rise with 6.6 feet of SLR

Short title; Author(s), Date

Observed depth to gw and simulated depth to gw with 6.6 feet of sea-level rise

29

Short title; Author(s), Date

Transect of the off-ramp from I-95 through the Portsmouth Circle

30

Short title; Author(s), Date 31

Sections of roads where the groundwater table is already shallow are the most vulnerable

Short title; Author(s), Date 32

Location of a pavement profile along Route 286

Short title; Author(s), Date 33

Route 286 – Pavement Profile

Short title; Author(s), Date

What factors make coastal road infrastructure vulnerable to changes in climate?

34

Proximity to the ocean

Locations where groundwater is near the

ground surface and where groundwater is

projected to rise

Inadequate stream crossings now or in the

future

Subgrade soil types that weaken with

increasing moisture content

Short title; Author(s), Date

Other concerns . . .

35

Short title; Author(s), Date

Will drinking water supplies be harmed by saltwater intrusion?

36

Area where GW is predicted to rise the most with SLR

Areas potentially at risk from saltwater intrusion with SLR

Short title; Author(s), Date

Rise in GW with 6.6 feet of SLR

37

Why doesn’t the GW rise as much here?

Short title; Author(s), Date

Increase in GW level is reduced in the proximity of streams, but. . .

38

• Streamflow will

increase.

• The freshwater/salt

water interface

may move further

inland.

Short title; Author(s), Date

Where might rising groundwater come in contact with contaminated soils?

39

Short title; Author(s), Date

Conclusions

40

Groundwater modeling is an effective tool for investigating

hydrologic changes resulting from climate change.

Rising groundwater and changing flow patterns will have

important consequences for the structural integrity of

infrastructure, water supply and water quality, stream base flow,

and the health of natural ecosystems.

Adaptation strategies must consider potential damage from rising

groundwater in addition to surface water impacts.

Short title; Author(s), Date

What actions can communities take . . .

41

Formally consider groundwater predictions when:

designing or repairing road infrastructure,

establishing criteria for the cleanup of contaminated sites

permitting onsite septic systems, and

designing sea walls or other protective structures to mitigate

damage from sea-level rise

Short title; Author(s), Date

What actions can communities take . . .

42

Identify drinking water supply wells that may be at risk from saltwater

intrusion and plan for alternative sources, if necessary

Identify the critical infrastructure in your community where rising

groundwater may cause problems

Protect existing wetlands and adjacent areas to allow for wetland

expansion

Collaborate with research institutions, community planning organizations,

government, and private partners to plan for the future

Short title; Author(s), Date

Acknowledgements

43

• NH Sea Grant is funding this project

• UNH – ICNet, UCIRC, the Asphalt Research Group, the

Climate Change and Infrastructure Research Group

• NH Seacoast Transportation Climate Working Group (NHS

TCWG)

• NH Coastal Adaptation Workgroup (NH CAW)

• NH Department of Transportation (NHDOT)

• NH Department of Environmental Services (NHDES)

• Thomas Mack and Dave Bjerklie of USGS

• Gregory Barker, NH Geological Survey

Short title; Author(s), Date

Thank you Questions?

Contact: Jayne F. Knott

University of New Hampshire jfk1011@wildcats.unh.edu

44