Historic Land Reclamation in the Intertidal Wetlands of the Shannon Estuary, Western Ireland

UCC Library and UCC researchers have made this item openly available. Please let us know how this has helped you. Thanks! Title Historic land reclamation in the intertidal wetlands of the Shannon estuary, western Ireland Author(s) Healy, Michael; Hickey, Kieran R. Publication date 2002 Original citation HEALY M. & HICKEY, K. R. (2002) Historic land reclamation in the intertidal wetlands of the Shannon estuary. In: Cooper, J. A. G., and Jackson D. W. T. (eds.), Proceedings from the International Coastal Symposium (ICS) 2002 (Templepatrick, Northern Ireland). Journal of Coastal Research, Special Issue No. 36, pp. 365-373 Type of publication Conference item Link to publisher's http://www.jcronline.org/page/special_publications version Access to the full text of the published version may require a subscription. Rights © 2002 Coastal Education and Research Foundation, Inc. (CERF) Item downloaded http://hdl.handle.net/10468/2521 from Downloaded on 2021-09-26T22:53:02Z Journal of Coastal Research SI 36 365-373 (ICS 2002 Proceedings) Northern Ireland ISSN 0749-0208 Historic land reclamation in the intertidal wetlands of the Shannon estuary, western Ireland Michael G. Healy† and Kieran R. Hickey‡ †Department of Geography Mary Immaculate College, University of Limerick, Ireland ‡ Department of Geography, National University of Ireland, Galway, Ireland ABSTRACT There is abundant landscape evidence for extensive land reclamation conducted within the Shannon estuary wetlands. To date, little published research is available which identifies how much reclamation has occurred, its timing and the likely environmental implications. This paper addresses these questions on the basis of available cartographic and documentary data on land reclamation in this area. Identification of reclaimed land was based on the 2nd Edition Ordnance Survey of Ireland Map Series of 1924. These maps represent landscape features relating to reclamation, such as embankments, artificial arterial drainage channels and sluices. Using such indicators for the purpose of demarcation, the extent of the lands reclaimed has been mapped. Documentary information on reclamation schemes was acquired from the National Archives files on the Irish Quit Rent Office, including letters, memoranda, draft bills and Government Acts, legal documents and statements of account, and these support and supplement cartographic data. In total, approximately 6,500ha of the Shannon estuary lowlands were reclaimed for agriculture and other purposes. This has significantly altered the morphometric characteristics of the estuary, as embankments and revetments for flood protection have reduced the potential energy dissipation area and the water storage capacity of the estuarine wetlands. Reclamation has resulted in modification of the estuarine physical environment and its hydrodynamics, and altered the character of the wetland habitat in the estuary environs. ADDITIONALINDEXWORDS: estuaries, reclamation, land claim, wetlands, embankments, drainage, cartography, historical evidence INTRODUCTION Aims Anthropogenic influences appear to have played a Extensive land reclamation works have been carried out significant role in the evolution of the Shannon estuary in the Shannon estuary over several centuries, possibly lowlands. O’ SULLIVAN (2001) documents a body of beginning as far back as the 10th/ 11th centuries. However, archaeological evidence that indicates long-term use of the detailed research to identify precisely how much estuary by humans. It appears that settlements existed reclamation has occurred, when it occurred and what were around the estuary from at least Neolithic times, with the likely environmental implications of human intervention attendant deliberate manipulation of the local environment. in the estuarine environment has not been published to date. It is almost certain that local wetland succession patterns This paper addresses this deficiency in the literature through were affected by early rudimentary agricultural activities, an analysis of cartographic and documentary data relating to producing consequent morphological responses within the land reclamation and drainage in the Shannon estuary area. estuary system. Technological advances through time are likely to have increased the potential for human THE CONTEXT FOR RECLAMATION IN intervention, though the scale and significance of ESTUARIES prehistoric human-induced environmental change still remains speculative. Estuarine geomorphology Coastal zones and ‘coastlines’ are transient in time (CARTER, 1988). The estuaries of western Europe were l a rgely formed following the rapid recovery of early Holocene relative sea-level, and their form and function Journal of Coastal Research, Special Issue 36, 2002 Estuary Land Reclamation 366 remain closely related to sea surface elevation. An abundant Wetland reclamation in estuaries supply of offshore glacigenic sediment allowed significant It has been estimated that c. 50% of the population of the sedimentation of estuarine basins to take place, a process industrialised world lives within 1 km of the coast, a often augmented by additional sediment supply from fluvial substantial proportion being located around estuaries. This sources. Estuary morphodynamics therefore reflect the gives rise to concerns about the management of the coastal relative balance between competing marine and fluvial resource, including the issues of shoreline erosion and sea processes (COOPER, 2001). The relatively sheltered defence, habitat degradation, pollution and reduction of character of estuarine environments, in particular where coastal biodiversity (HEALY, 1995; SMITH and WARD, tidal currents are weak, allows sediments to flocculate and 1998). On a global scale, pressure on the coastal land fall out of suspension. This process has resulted in the resource has frequently resulted in reclamation of the widespread development of mudflats and sandflats in coastal lowlands, particularly, but not exclusively, within European estuaries, though there is considerable variability estuarine environments (e.g. PETZELBERGER, 2000). among estuaries in the pattern and distribution of their Large areas of salt marsh have been reclaimed, such as low- sedimentary structures, depending, inter alia, on lying areas around the Irish Sea and the English Channel, topography, sediment supply, turbidity and current flows. and most notably in the Netherlands (VILES and Changes in the configuration of estuary bedforms and SPENCER, 1995; ALLEN, 1998). channels occur routinely, as well as similar changes in In the UK reclamation (sometimes referred to as ‘land associated salt marsh environments. Estuarine landforms claim’) on estuaries and coasts has been carried out at least are commonly constrained by retaining walls at high tide since Roman times (DAVIDSON et al., 1991). BORER levels, as well as training walls and embankments that are (1939) reports extensive land reclamation around the Wash used to fix channel positions. These nullify the natural from the 17th Century onwards. It would appear that initial tendency of mudflats, sandflats and their associated channel phases of reclamation sought to enclose salt marshes and systems to migrate in space and time, responding to mudflats with earthen banks for agricultural purposes changing estuarine morphodynamics. Consequently, (KING, 1959), by a process such as that described by estuarine morphology has become increasing inflexible in UDNEY (1831) for formal intertidal flats adjacent to the responding to natural coastal change. This problem is Forth estuary, Scotland. These works have been extensive exacerbated by the process of reclamation of estuarine flats and progressive in Britain through the centuries, accounting for agricultural, industrial and commercial purposes in for much of the estuarine habitat loss. Of the 155 British recent centuries, as described by DAVIDSON et al. (1991) estuaries, it is accepted that 136 (or 88%) have experienced for the UK. habitat loss to agricultural reclamation. DAVIDSON et al. (1991) report the scale of these changes at a variety of sites ( Table 1). Urban development and port and harbour Table 1. Habitat loss in English estuaries (Adapted from infrastructure have had significant impacts. More recently, DAVIDSON et al., 1991) reclamation for industrial, commercial and recreational uses has taken place, as well as works for suburban expansion Estuary Name Area lost (ha) Reclamation Period and housing development. The Wash 47,000 Since Roman Times In Ireland, outside of the Shannon estuary area, the Severn Estuary c. 8,000 Since Roman Times majority of land reclamation works have been concentrated Dee Estuary 6,000 Since 1730 on the east and south-east coasts (MULRENNAN, 1989; Humber Estuary 4,600 1600-1850 FURLONG, 1996; ROWE and WILSON, 1996). Of these Greater Thames Estuary 4,340 Mostly pre-1800 Tees Estuary 3,300 Since 1720 the most extensive and significant works were carried out Ribble Estuary 2,320 Since 1800 around Wexford Harbour. According to FURLONG (1996), Morecambe Bay 1,320 1200-1900 efforts to reclaim land from the harbour are first recorded in Ore/Alde/Butley Estuary 3,640 Since 1200 1813, with subsequent works in 1814-1816, 1840-1851 and Deben Estuary 2,240 Since 1200 1854-1870. In all, it appears that in excess of 2000 ha were Stour Estuary 1,600 Since 1200 reclaimed to produce the North Slob and South Slob around Blyth Estuary 1,280 Since 1200 Wexford Harbour. These works indicate the degree of Orwell Estuary 980 Since 1200

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