Abstract. 1 Introduction

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1 Prevention of hydrocarbons sea pollution: Sensitivity Index Maps for the Venice Lagoon as integral component of oil-spill contingency planning and response F. Cinquepalmi, D. Schiuma, D. Tagliapietra, C. Benedetti and University Institute of Architecture of Venice (I. U.A. V.) - S. Croce 1957, Venice, Italy. Italian Ministry of the University and Scientific and Technological Research (MURST); Venice Lagoon System Project (DAEST-IUAV). cinpalmi@iuav.unive.it, donna@iuav.unive.it, davidet@iuav.unive.it, cbenedet@ronet.it, ^ ^andreina@iuav.unive.it (Coordinator) Abstract In Italy the international regulations governing the transport of dangerous liquids by sea are strictly enforced and there are specific sets of safety rules for each port. Oil-spill risk management procedures could be further improved by the application of Environmental Sensitivity Index mapping principles to the assessment of coastal vulnerability. The aim of this project is the development of an Environmental Sensitivity Index (ESI) for the Venice Lagoon and the creation of Sensitivity Maps using GIS technologies. 1 Introduction Venice stands on a group of islands in a lagoon formed 6000 years ago in the north-east Adriatic. The present-day brackish lagoon covers about 570 sq.km. and is connected with the sea through three inlets at Chioggia, Malamocco and the Lido; these are demarcated by long jetties on either side and are kept practicable by outer breakwaters. Over 75% of the lagoon is less

2 198 Environmental Coastal Regions than 1m deep and navigation channels vary in depth from 5m to 20m at the Malamocco inlet. Since the first half of the 20th century intensive economic and industrial development has transformed the lagoon; about a third of the mudflats have gradually been reclaimed, channels serving the industrial port have been deepened and a vast industrial zone focused on energy production and the petro-chemical industry has grown up along the mainland side of the central part of the lagoon. The inestimable historical, landscape and environmental values embodied in the Venice Lagoon co-exist with increased anthropic pressure along its mainland shore due to the expansion of the chemical and petro-chemical industries in Porto Marghera. Currently, approximately 20 million tonnes of crude oil and bulk shipments of dangerous liquid chemicals are transported across the lagoon every year; in addition there are about 10,000 motorized craft of all sizes operating permanently within the lagoon basin. The situation constitutes a high-risk potential for a catastrophic oil spill and the certainty of continuous sub-acute spillage. 2 An integral component of oil-spill contingency planning and response: Sensitivity Index Maps for the Venice Lagoon Environmental Sensitivity Maps have been used since as far back as 1979 as an integral component of measures for the prevention of oil spills and for planning contingency response mechanisms in case they do occur. Environmental Sensitivity Index (ESI) atlases have been prepared, for example, for most of the American coast, including Alaska and the Great Lakes ^\ and for representative sections of the coast of several other countries, including Canada ^\ France ^ and Germany ^\ In Italy the international regulations governing the transport of dangerous liquids by sea are strictly enforced and there are specific sets of safety rules for each port. Oil-spill risk management procedures could be further improved by the application of Environmental Sensitivity Index mapping principles to the assessment of coastal vulnerability. The Venice Lagoon and the Upper Adriatic are particularly vulnerable areas given the intensive traffic of oil and dangerous cargo vessels. Previous studies have provided an analysis of the historical series of oil spills in the Venice Lagoon and of the probability and possible consequences of a full-scale catastrophe^. They also developed a plan for controlling oil tanker traffic in the Adriatic in order to prevent accidents and consequent pollution of the sea^

3 2.1 The basic elements of a sensitivity mapping system Environmental Coastal Regions 199 The aim of this project isfirstto identify the parts of the lagoon system that are most vulnerable to oil spill damage and to establish the basic elements - the criteria and scale of the survey and of the representation - for the development of an Environmental Sensitivity Index (ESI) for the Venice Lagoon and for the creation of Sensitivity Maps using GIS technologies. The sensitive aspects of each of the constituent elements of the lagoon system were identified and assessed in terms of risk, impact and damage. Assessment of the sensitivity of the Venice Lagoon is based on criteria that are usually considered fundamental: the risk factor, determined in terms of the morphological, physical, chemical, sedimentological and topological characteristics of the lagoon ecomosaic (natural and anthropic components) and in relation to the difficulties attached to Clean-up; the biological and/or anthropic value factor, which represents the potential damage that the system could suffer. A third specific element was taken into consideration as an amplification of the potential damage factor: the anthropogenic factor, i.e. the socio-economic and historical-cultural values that are specific to the city of Venice and its lagoon and make them unique. It was decided to use a scale of representation that could include all the main constituent parts of the lagoon, from the sea to the sandy coastal shore, the inlets, the morphological features of the intertidal transitional zone, the historic island settlements and the fishfarms. 3 The lagoon ecosystem: natural and historical features The natural morphological structure of the Venice Lagoon depends on its relationship with the sea, from which it is separated by a discontinuous sandbar of dunes and beaches. Being a micro-tidal coastal basin, subject to a twice-daily tidal cycle, the lagoon has acquired characteristic morphological features such as tidal flats, mudflats, salt marshes, marshes and islands, which began to support human settlements from the 4th century BC.

4 200 Environmental Coastal Regions Transactions on Ecology and the Environment vol 18, 1998 WIT Press, ISSN Natural features The transition wetlands and intertidal environment areas represent very important habitats and form the natural landscape of the Venice Lagoon. In constructing the ESI matrices we considered the following natural morphological features: Coastlines (table 1, matrix 1): - seabed close to shore; - beach/shore. Natural intertidal elements (table 1, matrix 2) - low marshes; - high marshes; - islets; - mudflats; - brackish marshes. 3.2 Stretches of water Navigable channels of varying depths constitute the main communications network; there are water-based economic activities such as aquaculture and fishfarms, while cultural and recreational activities include rowing and fishing. It was decided that stretches of water with such significance should be identified in the Sensitivity Index and should be distinguishable on the maps. In constructing the ESI matrices we considered the following stretches of water (table 2, matrix 3): major navigational channels; tidal channels/marsh creeks; mudflats; open waters; brackish basin; secondary channels; fish farms. 3,3 Artificial features The insulae of the city are entirely built up withpa/azz/, churches and lesser buildings of inestimable historical and architectural value, built and modified over many centuries; their facades rise directly from the water of the canals and so are subject to the risk of erosion and soiling. The phenomenon of acque alte brings the flooding first of the city streets and squares and then of the ground floors of the buildings. Paving is mainly of stone slabs and brick laid at least two centuries ago, and fine marble flooring is often literally irreplaceable in that the quarries it came from are now worked out; all this is at severe risk in case of oil spillage.

5 MATRIX 1 Coastlines ESI FOR NATURAL MORPHOLOGICAL FEATURES i CLASSES Tide helgl > 100 cm i /100 cm 13,3 25/50 cm 20,0 25/25 cm 4 26,7 26,7 2-25/-50 cm 3 20,0 20,0-50/-100 cm 2 13,3 % K Angle of slope 15"><45" ,7 5'><15' <5' w Wave movement J0N 1 16,7 average high Risk value h < w3 clean up sand 2 40,0 40,0 pebbles/shells 3 60,0 60, Impact and Risk - physical sensitivity Low nature llstlc/blologlcal value / 0, Low water quality 2 0, ju Recre; rtlonal/aesthetlc value3 0, Presence of economic activities 456 1, O Good vwater quallty/bathlnge 1, i c* am harvesting/fishing 1, Landscape value 7 1, Naturalistic value 8 2, Local blrdllfe 9 2, Nature reserve 10 2, MATRIX 2 ESI FOR NATURAL MORPHOLOGICAL FEATURES Tide height (0 I ec 3 OT CLASSES > 100 cm 50/100 cm 25/50 cm -25/25 cm -25/-50 cm -50/-100 cm Angle of slope 15'><45" 5'><15' <5' Wave movement low average high Risk value < huj 3 clean up of g $ the substrats peat/mud/clay pebbles/shells Impact and Risk - physical sensitivity Low nature llstlc/blologlcal value Low water quality jjs Recresttlonal/aesthetlc value z Presence of economic activities $ Goodswater quallty/bathlnge 1 ciam harvesting/fishing Landscape value Naturalistic value Local blrdllfe Nature reserve Standardized wetgtiug I I? I 1 6,7 2?3,3 3 20,0 4 28,7. 26,7 ' 3 20, ,7 _ , , ,25 0,60 0,76 1,00 1,25 1,50 1,76 2,00 2,25 2, Endolagunar Intertidal elements 13,3 I fl 6,7 16, , _2p^0 41>8J I ESI I 122>292 I ESI >375 Esim ESI IV 16, ,3 16, >72 57 ESI I >14J 142 ESI n S0> ESI ra >J \ ESI IV Table 1: the two matrices for the natural morphological features (matrix 1 for coastlines and matrix 2 for endolagunar intertidal features).

6 202 Environmental Coastal Regions In constructing the ESI matrices we considered the following artificial features (table 2, matrix 4): Structures in the sea; - jetties and breakwaters at the lagoon inlets. Island settlements; horizontal contact structures; vertical contact structures. 4 Risk factors and impact elements for the Venice Lagoon The tide ebbs and flows through the three inlets and along the channels of the lagoon, registering a half-cycle high- and low-point delay of about two hours in the parts furthest from the sea. The average astronomical amplitude is about 50 cm and reaches the natural wetlands and Venice approximately one hour after entering the lagoon. When normal conditions are distorted by scirocco and bora winds - from South and North respectively - Venice and Chioggia and the smaller islands of Murano and Burano are subject to flooding. Being just 80 cm above mean sea level, St. Mark's Square is the part of Venice mostfrequentlycovered by water. 4.1 Risk assessment criteria for cases of oil spillage Hydrodynamic conditions were taken as the guiding parameter in assessing the risk to the various natural and artificial morphological features and water stretches of the lagoon from contact with oil slicks. They have all been put in an order of increasing risk according to the potential frequency of exposure, the nature and form of the contact surface and substrata, wave movement and depth. The various classes of risk were given relative values on a scale of In constructing the ESI matrices for the risk run by shorelines and natural intertidal features, we identified three factors, each sub-divided in classes (table 1, matrices 1 and 2): tide height, with classes from 1 to 4 related to increasing frequency of contact; slope of contact surface, with classes from 1 to 3 in inverse relation to the angle of slope; wave movement, with classes from 1 to 3 related to high, medium and low energy action. In constructing the ESI matrices for the risk run by stretches of water, we identified two factors, each sub-divided into classes (table 2, matrix 3): depth of lagoon bed, with classes from 1 to 4;

7 MATRIX 3 ESI FOR WATER STRETCHES CLASSES deepness -0,25>-1 m U4 Of -1>-2m 2>- 10m < 10 m S 5 ^ u. wave tow 2 movement average high h uj ^ a Risk value clean uppeat/mud/clay sand/shells Impact and Risk physical sensitivity low water quality barren lagoon-bed x flshlno facilities o recreational value uj clam harvesting fishing facilities < hunting high water quality veaetation-suodorhna laaoon-bed aquaculture If I CO t? 4 40 ll I JC 1C t/i 40,0 40, ,0 30, ,0 20, , f2 16J ,7 16, _%3_ , ,25 0,50 0,75 1,00 1, ,75 2,00 2,25 2,50 MATRIX 4 ESI FOR MORPHOLOGICAL ARTIFICIAL FEATURES CLASSES! 55 tj levels >115cm 4 40 above m.s.l. 100/1 15cm 3 30 UJ cm cc <85cm 10 w g o contact vertical horizontal and vertical frequency exceptional 1 17 rare 2 33 high Risk value 3 clean upmedium monuments high Impact and Risk for phlsical sensitivity /. h. presen ce of service functions 1 0,25 2 0,50 o presence of economic activities 3 0,75 UJ 4 1,00 % presenc e of cultural functions 5 1,25 6 1,50 presen ce of landscape values 7 1,75 8 2,00 features of h Istoricat/monumental/ 9 2,25 architectural importance 10 2,50 66, secondary channels I horizontals 20J? II 30, III 40,0 77, f IV 10, verticals V 20, VI 30,0 77,0 80 J#0_ Jetties VII 10,0 127 J3, O133 ESI I 127>317 ESI II 28>153 ESI I 158>255 ESI II 2S4>S10 ESI III Table 2: the two matrices for the water stretches (matrixs) and for the morphological artificial features (matrix 4)

8 204 Environmental Coastal Regions wave movement with classes from 1 to 3. In constructing the ESI matrices for the risk run by artificial features, we identified three factors, each sub-divided into classes (table 2, matrix 4): height with respect to mean sea level, with classes from 1 to 4 related to tide height and flooding; contact surfaces, with classes from 1 to 2 related to the vertical or horizontal angle of the surface; frequency of contact, with classes from 1 to 3 in inverse relation. A risk factor - the sum of the standardized weightings of the classes attributed - was estimated for each of the categories considered in the matrices. 4.2 Impact assessment criteria in case of oil spillage and Sensitivity Index The impact factor was assessed in relation to the possibility and the difficulty of mounting successful Clean-up operations. As regards the assessment of impact on natural features, the ESI matrices classify them into three groups in relation to the nature of the sub-stratum and the degree to which it will absorb and retain oil (tables 1 and 2, matrices 1, 2 and 3): substratum of peat/mud/clay; substratum of sand substratum of pebbles/shells. As regards the assessment of impact on artificial features, the ESI matrices classify them into two groups according to the difficulty of Clean-up. The capacity of these surfaces to absorb oil increases in relation to their roughness and poor state of conservation. Buildings that have not been properly maintained or restored often feature damage, cracks and serious lacunae. Almost all the buildings concerned are very old, some dating from the 9th century. The various classes of impact were given relative values on a scale of An impact and risk factor - the sum of the standardized weightings - was estimated for each of the categories considered in the matrices; this represents the physical sensitivity of the system. 5 Assessment of oil spill damage in the Venice Lagoon In the case of pollution caused by oil spill, the term damage is used to describe the partial or total loss of value of natural, biological, anthropic and anthropogenic items in the Lagoon as identified by the summary quality descriptors illustrated below.

9 Environmental Coastal Regions 205 Damage weightings or indices have been attributed to each of these descriptors, increasing in proportion to the degree of seriousness and irreversibility of the loss of value. In the matrices the damage indices have been standardized to 100 on a base of 2,5. For natural features reference has been made to an appropriate system of descriptors of the type, morphological and biological complexity and value of the natural systems of the Venice Lagoon, and of their values in terms of landscape/culture and use. The highest damage values have been attributed to naturalistic values and to the natural reserves (table 1, Matrices 1 and 2). For stretches of water reference is made to a system of descriptors related to the principal activities connected with them. Important traditional economic activities include fishing, fish farming and aquaculture of mussels and shellfish, the harvesting of clams and hunting. The highest damage values have been attributed to the more important economic activities that depend on good water quality (table 2, Matrix 3). In the case of anthropic values, the descriptors used refer to historical, monumental and architectural factors, to the degree to which the item is an integral part of the enjoyment/use of the landscape/culture and to the presence of legal protective measures. All the more important cultural events in Venetian life are closely connected with water, including sporting events and regattas commemorating historical and religious anniversaries. As regards anthropogenic values (artificial structures), the highest damage indices relate to the loss of historical-monumental and architectural items (flood-borne oil pollution in St.Mark's Square) (table 2, Matrix 4). 6 The Environmental Sensitivity Indices (ESI) Environmental Sensitivity Indices are the result of the analysis of numerical values obtained with two-dimensional matrices, from the meeting point of physical sensitivity indices (the sum of the standardized risk and impact values) and the damage indices. Discrete analysis of the matrices enabled the numerical values to grouped into clusters. These define the environmental and historical-cultural sensitivity of the morphological structures analyzed. The value groupings then provide the basis for the definitions and descriptions condensed in the Environmental Sensitivity Indices (ESI) following the widely accepted procedures developed by the NOAA. Four sensitivity matrices are presented, two for natural morphological structures, the first of which refers to the coastline (table 1, Matrix 1), the second to endolagunar intertidal elements (table 1, Matrix 2), the third for stretches of water (table 2, Matrix 3) and the fourth for artificial morphological features (table 2, Matrix 4).

10 206 Environmental Coastal Regions 7 Conclusions On the basis of the risk factors and assessment of the damage to the morphological structures characterizing the natural and anthropic components of the Venice Lagoon, the following Environmental Sensitivity Indices (ESI) were identified: For the coast-line: ESI - I. beaches and seabed close to the shore with low naturalistic/biological value and low water quality ESI - II. beaches and seabed close to the shore with recreational/aesthetic value, with the presence of economic activities, with good water quality, also for bathing, with clam harvesting and fishing and with landscape value. " ESI - III. beaches and seabed close to the shore with naturalistic value and local birdlife and with the presence of a nature reserve. For natural morphological features: ESI -1. all intertidal elements support no or little vegetation and poor level of wild life and exchange. ESI - II. all intertidal elements of medium morphological and biological complexity, marshes with cultural and recreational value. ESI - III. all intertidal elements support vegetation, have cultural and recreational value; low-lying natural and artificial islets, mudflats and marshes all with flourishing wild life. ESI - IV. tidal flats and marshes with flourishing wild life and all intertidal elements with high morphological and biological complexity and with naturalistic value. For stretches of water: ESI - I. all the stretches of water of low water quality and supporting no vegetation that can nevertheless support fishing facilities and have recreational value, marshes, secondary channels, fish farms and clam harvesting. ESI - III. all the stretches of water with high water quality, used for clam harvesting, with vegetation-supporting lagoon-beds and used for recreational fishing and hunting. For the artificial morphological features: ESI -1. all the structures with mainly service functions and medium presence of economic activities. Vertical structures with high cultural and medium economic value. " ESI - II. all the horizontal structures with high economic activity and medium level cultural function. Vertical structures with high cultural value and medium-high landscape value.

11 Environmental Coastal Regions 207 ESI - III. all the horizontal structures with high cultural value and landscape, historical, monumental and listed building values. Listed vertical surfaces with high historical and monumental value. The ESI identified as above were used to create Environmental Sensitivity Maps (scale 1:25,000 - website V.ESI.Maps on in which lines and shading are used to identify the outlines and areas of the sensitive morphological features. The Sensitivity Index Maps have been created as a useful contribution to the prevention of pollution from oil spills and to combating the consequences if accidents should occur along the coast or in the Lagoon. They help to identify the more sensitive and higher priority environmental and historical morphological elements with a view to planning preventive action and emergency response in the case of accidents. References [1] Environment Canada, National Sensitivity Mapping Program (NSMP) Atlantic Region, Mapping Program (ARSMP), 1991/1997. [2] Groupe SILLAGE/IFREMER, Mise en forme numerique de I'Atlas des marais maritimes atlantique, Centre IFREMER de Brest, 1995 [3] Cinquepalmi, F., Campagnol, A. and Zitelli, A., AdriaOil Plan: a project for multilateral spill management in the Adriatic Sea, Proceedings of MEDCOAST '97, Qawra (Malta), Middle East Technical University, Ankara, Turkey, 1997; [4] Krasemann, H. L., Riethmuller, R., WATiS - The Wadden Sea Information System, Experience From an Operational System - in Climate and Environmental Database Systems, Kluwer Academic, Boston, [5] NOAA Technical memorandum - National Ocean Service (NOS) Office of Resources Conservation and Assessment (ORCA) 115, Environmental Sensitivity Index Guidelines version 2.0, Seattle (WA), [6] Zitelli, A., Cinquepalmi, F., Benedetti, C, Campagnol, A., Bergamasco, A., Oil spills in the Venetian Lagoon: an analysis of risk management^ in Proceedings of COASTAL ENGINEERING 97, Wessex Institute of Technology, La Corufia (Spain) 1997;