Local Flood Risk Management Strategy for Hertfordshire Strategic Environmental Assessment Scoping Report - October 2011 Annex B: Baseline Information © Hertfordshire County Council …………………………………………………October 2011 Produced by Essex County Council on behalf of Hertfordshire County Council The information contained in this document can be made available in alternative formats: large print, braille, audio tape or on disk. We can also translate this document into other languages. For further information please contact the Andy Hardstaff, Flood and Water Management Officer 01992 556470, or [email protected] © Hertfordshire County Council …………………………………………………October 2011 CONTENTS 1 Introduction .........................................................................................................1 1.1 Background ..............................................................................................1 1.2 Baseline Information.................................................................................1 2 Flooding ...............................................................................................................3 2.1 Impacts of Flooding in Hertfordshire.........................................................3 2.1.1 Surface Water Flooding ............................................................................3 2.1.2 Groundwater Flooding ..............................................................................3 2.1.3 Sewer Flooding.........................................................................................4 2.1.4 Historic Flooding Episodes .......................................................................4 2.1.5 Recent Flooding Episodes........................................................................5 2.2 District / Borough Strategic Flood Risk Assessments...............................5 2.2.1 Broxbourne Borough SFRA ......................................................................5 2.2.2 Dacorum Borough Council, St Albans City & District, Three Rivers District and Watford Borough SFRA .....................................................................6 2.2.3 East Hertfordshire District SFRA ..............................................................6 2.2.4 Hertsmere Borough SFRA........................................................................6 2.2.5 North Hertfordshire District SFRA.............................................................7 2.2.6 Stevenage Borough SFRA .......................................................................7 2.2.7 Welwyn Hatfield Borough SFRA...............................................................8 2.3 Flood Zones..............................................................................................9 2.4 Catchment Flood Management Policy Units...........................................12 2.5 Properties at Risk from Flooding.............................................................13 2.6 Areas Susceptible to Groundwater Flooding ..........................................16 2.7 Surface Water Flood Map of Hertfordshire .............................................18 2.8 EA Objections to Development in Hertfordshire .....................................20 2.9 Summary ................................................................................................23 3 Water Resources ...............................................................................................25 3.1 Inland Water Resources in Hertfordshire................................................25 3.1.1 Main Rivers.............................................................................................25 3.1.2 Aquifers ..................................................................................................26 3.2 Water Supply in Hertfordshire.................................................................28 3.3 Groundwater Levels................................................................................30 3.4 River Basin Management Plans .............................................................30 3.5 Sustainable Drainage Systems...............................................................33 3.6 Water Consumption................................................................................35 3.7 Summary ................................................................................................35 4 Population and Social Issues...........................................................................37 4.1 Population...............................................................................................37 4.1.1 Population Structure ...............................................................................37 4.1.2 Population Projections by ONS ..............................................................38 4.2 Indices of Multiple Deprivation................................................................40 4.3 Summary ................................................................................................42 5 Climatic Factors ................................................................................................43 5.1 Climate Change Projections ...................................................................43 5.2 Annual Mean Temperature .....................................................................48 © Hertfordshire County Council …………………………………………………October 2011 5.3 Annual Mean Precipitation......................................................................49 5.4 Key Projections for the Thames and Anglian River Basin Districts.........49 5.4.1 Implications of Flooding within the Thames River Basin District.............49 5.4.2 Implications of Flooding within the Anglian River Basin District..............49 5.5 CO2 Emissions........................................................................................50 5.6 Renewable Energy Resources ...............................................................53 5.7 Summary ................................................................................................55 6 Housing..............................................................................................................57 6.1 Future Dwelling Completion Trajectories in Hertfordshire.......................58 6.2 Summary ................................................................................................64 7 Biodiversity and Geological Conservation .....................................................65 7.1 The Hertfordshire Biodiversity Action Plan .............................................65 7.1.1 Hertfordshire Red Data List ....................................................................66 7.2 Land Designations..................................................................................66 7.2.1 Ramsar Sites ..........................................................................................66 7.2.2 Special Protection Areas and Special Areas for Conservation ...............68 7.2.3 Sites of Specific Scientific Interest..........................................................70 7.2.4 Geological Sites......................................................................................72 7.2.5 National Nature Reserves.......................................................................72 7.2.6 Local Nature Reserves ...........................................................................74 7.2.7 Local Wildlife Sites..................................................................................75 7.2.8 Ancient Woodland...................................................................................76 7.2.9 Watling Chase Community Forest ..........................................................77 7.3 Summary ................................................................................................78 8 Cultural Heritage ...............................................................................................81 8.1 Listed Buildings.......................................................................................81 8.2 Historic Buildings At Risk Register..........................................................82 8.3 Archaeology, Recorded Sites and Finds in Hertfordshire .......................83 8.4 Scheduled Monuments ...........................................................................83 8.5 Historic Battlefields .................................................................................84 8.6 Historic Parks and Gardens....................................................................84 8.7 Conservation Areas ................................................................................85 8.8 Summary ................................................................................................86 9 Soils, Minerals and Waste ................................................................................89 9.1 Hertfordshire Soil Type ...........................................................................89 9.2 Agricultural Soil Classification.................................................................90 9.3 Minerals ..................................................................................................91 9.4 Mineral Transportation............................................................................92 9.5 Waste Movements..................................................................................93 9.6 Active Waste Sites..................................................................................95 9.7 Strategic Waste Sites