PYLARINOU AIKATERINI FRENCH JON BURNINGHAM HELENE … · UCL DEPARTMENT OF GEOGRAPHY PYLARINOU...

UCL DEPARTMENT OF GEOGRAPHY

PYLARINOU AIKATERINIFRENCH JONBURNINGHAM HELENECoastal & Estuarine Research UnitEnvironmental Modelling GroupUniversity College London, UK


Sea-Level Rise (SLR)Even a small increase in sea level dramatic impacts on many coastalenvironments:Increased flood risk in deltaic region and urban centresSaltwater incursion into regional coastal areasIncreased erosion

Increase in intensity / frequency of stormsAlter surges and storm wavesIncrease wave height and extreme water levelsThe waves influence coastal sediment deposits:oEpisodic erosion and floodingoWetland degradation and loss

UCL DEPARTMENT OF GEOGRAPHYUCL DEPARTMENT OF GEOGRAPHY

Most affected areas: low–lying coastal and intertidalareas and especially the saltmarshes


EXPECTED RESPONSES OF SALTMARSHES TO SLR

1. Inland migration: As sea level rises, erosion occur in the outerboundary and new salt marsh will be formed inland

BUT when migration can not occur: Coastal Squeeze LAND LOSS

It has been estimated that 100ha of saltmarsh is presently lost due to thisso-called “coastal squeeze” every year

2. Vertical Accretion:• Vertical accretion = SLR no change • Sedimentation rate > SLR tend to move seaward • Sedimentation rate < SLR erosion and more frequent inundation


• To model the potential impacts of sea-level rise onUK coastal and estuarine habitats

• To visualize habitat changes in a way that isaccessible to stakeholders and the wider public


Modelling approaches

MATHEMATICAL MODELS

ANALYTICAL•Explicit solution of governingequations•Unsuited to complex /spatially-distributed problems

NUMERICAL•Computationally intensive•Can simplify representation ofcomplex processes (reducedcomplexity)•Suited to complex problems

EMPIRICAL•Simplest•Predicative skill exceedsexplanatory power

CONCEPTUAL

PHYSICALLY BASED•Physical principles•Explanatory power may begreater than predicative skill

UCL DEPARTMENT OF GEOGRAPHYCase study: Newtown Estuary, Isle of Wight

• Newtown Harbour habitat notified as Site of Special Scientific Interest (SSSI)

• Much of the Newtown estuary also designated as a National Nature Reserve that supports nationally important and threatened wildlife


• Previous study in the area: Environment Agency BRANCH project :

Combines GIS and remote sensing datasets to visualize simplified scenarios of sea-level change

This project lacked any physically-based modelling of habitat transitions under sea-level rise, being largely based on the progressive “drowning” of existing coastal topography.

• This project uses a spatial landscape model (SLAMM) in order to provide more robust insights into a large –scale coastal change at century scale and beyond


• Developed by Richard A. Park (1986) with United States EnvironmentalProtection Agency funding

• It is a rule-based spatial model that simulates the dominant processesinvolved in wetland conversions and shoreline modifications duringlong-term sea-level rise.

• It can estimate: the extent to which sea water inundation contributes to the conversion

of one habitat to another based on elevation, habitat type, slope,sedimentation and accretion and erosion rates, and

the extent to which the affected area is protected by existing sea walls.

The model has recently been used for very large area simulations in the USA and in Australia, on the scale of:

Chesapeake Bay, Puget Sound, Washington, and New South Wales, Australia


Uses six primary processes:1.Inundation : For each time step:•The sea level rise is calculated

• The relative sea level rise is calculated

MODEL OVERVIEW


2. Erosion: is triggered based on the maximum fetch and the proximity of the wetland to estuarine water or open ocean:

Fetch < 9km Erosion = None 9km <Fetch <20km Erosion = Heavy Fetch > 20km Erosion = Severe3. Overwash: assumed to occur in barrier islands of under 500 m width

during each 25 year time-step period as a result of storms4. Saturation: model assumes that fresh water marshes can migrate

onto adjacent uplands as a response of the water table to rising sea level close to the coast

5. Accretion: can be specified with 2 different waysi. spatially varying values for each type of wetlandii. accretion specified as a function of cell elevation, wetland type,

salinity and distance to channel6. Salinity: is used when fresh-water flow is significant and thus, the

marsh-type is correlated more to water salinity than elevation


BATHYMETRY

1.DEM GIS layer INTERPOLATION


DEM GIS layer


BATHYMETRY

1.DEM GIS layer

2. SLOPE GIS LAYER

INTERPOLATION

GIS


SLOPE GIS LAYER


BATHYMETRY

1.DEM GIS layer

2. SLOPE GIS LAYER

3. WETLAND CATEGORIES

LAYER

INTERPOLATION

GIS


WETLAND CATEGORIES LAYER


BATHYMETRYSLAMM

1.DEM GIS layer

2. SLOPE GIS LAYER


LAYER

INTERPOLATION

GIS

SLAMM INPUTS

SITE PARAME

TERS


SITE PARAMETERS


BATHYMETRYSLAMM

1.DEM GIS layer

2. SLOPE GIS LAYER


LAYER

INTERPOLATION

GIS

SLAMM INPUTS

SITE PARAME

TERS

Adopt UK wetland

elevation


UK wetland elevations


BATHYMETRYSLAMM

1.DEM GIS layer

2. SLOPE GIS LAYER


LAYER

INTERPOLATION

GIS

SLAMM INPUTS

SITE PARAME

TERS

SLR

Adopt UK wetland

elevation


SLR SCENARIOS• The simulation will be

based on the IPCC Special Report Emissions Scenarios (SRES).

• In this project the A1B SRES scenario will be used for the next 100 years at a time step of 25 years.


Assumes:rapid economic growth, low population growth and rapid introduction of new and more efficient technologies.

The A1 scenario family develops into three groups that describe alternative directions of technological change in the energy system and they are distinguished by their technological emphasis:Fossil intensive (A1F)Non-fossil energy sources (A1T) orA balance across all sources (A1B)


BATHYMETRYSLAMM

1.DEM GIS layer

2. SLOPE GIS LAYER


LAYER

INTERPOLATION

GIS

SLAMM INPUTS

SITE PARAME

TERS

SLR

OUTPUTS

Adopt UK wetland

elevation


• The coastal and estuarine habitat modelling of thisproject will produce a large number of spatialoutputs in the forms of maps, for each year, wherenew tidal and habitat boundaries will bedelineated for a period of 100 years as a result ofsea-level rise.


INITIAL CONDITION 2008 2025

2050 2075 2100


WETLAND TYPE % CHANGE FROM BASE YEAR 2008

Developed dry land -0.18Trans. Salt Marsh -20.62Irregularly flooded marsh -11.6Regularly Flooded Marsh 10.7Tidal Flat 0.2Ocean Beach -23.75Estuarine Open Water 2.94Open Ocean 4.5Vegetated tidal Flat -0.05

STATISTICAL OUTPUTS FOR EACH YEAR



TEST THE SPATIALITY OF THE MODELSpatial Accretion Model

Calculate the accretion rate (Acell) in each cell according to the:• Cell elevation • Distance to channel (D)• Salinity (if relevant) (S)

Acell=Aelev(D*S)where Aelev= accretion rate for a cell as a function of elevation alone

The SLAMM accretion relationships are empirically defined between rates of accretion and cell elevations:

32 )%1()%1()%1(

)(

changechangechangeelevation

shapeshape

Shapeelevation

accrAccraccrelev

ElevaElevbElevcShape

MinMaxMinShape

ShapePctil

MinMaxShapePctilMinA


After testing a range of a,b,c for the site, the appropriate are chosen and the shape of the curve is defined:


COMPARE THE SLAMM WITH AND WITHOUT THE SPATIAL ACCRETION MODEL

The spatiality of the model mainlyinfluences the habitats that are closer to theestuarine water


Will provide the coastal management communitywith a computationally efficient yet powerfulmethodology with whichto prioritize risk management strategies,reformulate sea defence “set back” requirements,improve guidelines for construction of coastal infrastructure, and assess habitat resource impacts and protection needs.


THANK YOU

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