4. Strategic Flood Risk Assessments

4.1 Objectives Historically, the management of flood risk in the UK has been undertaken in a somewhat reactive manner, addressing problems on an ‘as needed’ basis in response to a flooding event. It was recognised by Government that, in general, this was not a particularly cost effective approach and often failed to consider individual problem areas within the bigger picture of the wider hydrological system. The Environment Agency has therefore committed to a rolling programme of flood risk assessment (mapping) and strategic flood risk management investigations, including Catchment Flood Management Plans (CFMPs) and PAG2 Flood Risk Management Strategies5 within fluvial (river) systems. These studies take a catchment-wide approach, identifying where flooding is known and/ or perceived to be an existing problem, how this flooding regime may alter in future years as a result of climate and land use change, and how flooding can be managed cost effectively and sustainably over the next 50 to 100 years. On a local planning level, SFRAs consider the flood risk within the local area and, through the Sequential Test detailed in PPG 25 and the emerging PPS 25, allow LPAs such as Pendle Borough Council to direct development whilst controlling flood risk. More detailed Flood Risk Assessments (FRAs) would then be undertaken for the selected sites when and if they are developed. The SFRA should not contradict broader catchment scale recommendations of a CFMP and planning directed by the SFRA should fit within CFMP objectives. However, since SFRAs are specific to administrative areas they can pay more attention to secondary sources of flooding (such as overland flow, sewer and groundwater flooding) than CFMPs.

4.2 General Approach

4.2.1 Introduction The SFRA is a planning tool. It is an assessment of flood risk to inform the spatial planning process, and therefore the degree of detail and accuracy should be commensurate with this objective. A pragmatic and risk-based approach is recommended. The assessment of flood risk within a Borough should be targeted to those areas where development pressure is proposed within current planning horizons. Furthermore, the accuracy sought with respect to the delineation of flood risk should be sufficient to ensure confidence in the findings and recommendations of the SFRA, and it should also be reasonable within the context of the intended end use of the document to inform the allocation of sites within the LDF.

5 FCDPAG2 Strategic Planning and Appraisal, part of the series Flood and Coastal Defence Project Appraisal Guidance, DEFRA, April 2001.

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The LPA, supported by advice from the Environment Agency, must ensure flood risk is managed appropriately and effectively during the planning process. To facilitate this, and to inform the planning process, the ODPM expects LPAs to undertake a sequential flood risk test when planning development as outlined in PPG 25 and the emerging PPS 25. PPS 25 states (section 2, paragraph 13): “A sequential approach to determining the suitability of land for development in flood risk areas is central to the guidance and should be applied at all levels of the planning process.”

4.2.2 The PPS 25 Sequential Test and Exception Test PPS 25 sets out a robust approach to the Sequential Test that is core to the SFRA process and intended to provide a rigorous understanding of local flood risk. It is based on Environment Agency flood zones, which delineate areas by their level of risk due to river and sea flooding. Table 4.1 summarises these zones.

Table 4.1 PPS 25 Flood Risk Zones

Zone Criteria Appropriate Land Use Vulnerability 1

Zone 1 Land with a < 0.1% chance of river All land uses and sea flooding in any year. Low Probability

Zone 2 Land with between a 1% and 0.1% Water compatible, less vulnerable and more vulnerable chance of river flooding or land uses Medium Probability between a 0.5% and 0.1% chance of sea flooding in any year. Highly vulnerable land uses only if the Exception Test is passed

Zone 3a 2 Land with a > 1% chance of river Water compatible and less vulnerable land uses flooding or a > 0.5% chance of sea High Probability flooding in any year. More vulnerable land uses and essential infrastructure only if the Exception Test is passed

No highly vulnerable land uses

Zone 3b 3 Land where water has to flow or Water compatible land use be stored in times of flood. Functional Floodplain Essential infrastructure only if it must be in this location and the Exception Test is passed

No less vulnerable, more vulnerable or highly vulnerable land uses

1 See Appendix B for land use vulnerability classification. 2 PPG 25 Zones 3a and 3b have been merged into PPS 25 Zone 3a. 3 PPG 25 Zone 3c is PPS 25 Zone 3b.

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The overriding aim of the Sequential Test is to steer all new development to the lowest flood risk zone (i.e. zone 1). Where it is not possible to locate development in zone 1, development may be considered in zone 2 and then zone 3 if there is no available alternative in a lower risk zone. The Sequential Test constrains such development based on the vulnerability of the proposed land use, with the more vulnerable land uses restricted to zones of lower risk. Table 4.1 indicates the appropriate land use vulnerabilities for each zone. Appendix B lists land uses according to the vulnerability classification used in the Sequential Test. Depending on the land use vulnerability, there may be a further requirement to satisfy the Exception Test outlined in PPS 25 prior to development in these higher risk zones (as indicated in Table 4.1). “The Exception Test is that: a) The development makes a positive contribution to sustainable communities, and to sustainable development objectives of the relevant LDD…; b) The development is on developable brownfield land or where there are no reasonable alternative options on developable brownfield land; c) A flood risk assessment demonstrates that the residual risks of flooding to people and property (including the likely effects of climate change) are acceptable and can be satisfactorily managed; and d) The development makes a positive contribution to reducing or managing flood risk.” The Exception Test should be applied as early in the planning process as possible, and should not be used to justify ‘highly vulnerable’ development in zone 3a, or ‘less vulnerable’, ‘more vulnerable’ or ‘highly vulnerable’ development in zone 3b. Where development is planned in the higher risk zones, flood management and mitigation measures may be required to reduce risks to an acceptable level. Types of measures could range from traditional flood defences and flood alleviation schemes, to flood resistant and resilient design, and emergency plans. Where either existing or proposed measures are in place, the Sequential Test requires a demonstration that the residual flood risk (i.e. after taking the management and mitigation measures into account) is acceptable. In addition, the potential for climate change to impact on flood risk must also be considered. Development in all zones, both low and high risk, must also consider flood risks other than those due to river and sea flooding (e.g. overland flow, sewer and groundwater flooding) and apply a sequential approach to these risks if present. In addition, the implications the development has for flood risk elsewhere due to its drainage and runoff must also be considered. The application of the Sequential Test taking land use vulnerability into account, together with the Exception Test, forms a rigorous process for assessing and prioritising the location of planned development with respect to flood risk. If required, the Sequential Test can be undertaken as an iterative process, using greater resolution and understanding of the flood risks, and after testing how effective any management or mitigation measures might be. In the context of an SFRA, the application of the Sequential Test is restricted to a strategic level to inform the spatial planning process. The specific flood risk issues associated with potential development sites identified through the SFRA process will then be assessed in more detail via a site-specific FRA as part of the planning application.

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4.3 Approach for Pendle Borough The following key factors relating to development and flood risk influenced how the SFRA approach was tailored to Pendle Borough: • A history of significant fluvial flood events, but also known incidents of flooding due to other mechanisms, in particular overland flow and blockages or insufficient capacities of culverts and bridges; • Flood alleviation schemes on Walverden Water (planned) and Pendle Water (implemented); • The recent enmainment of nine critical ordinary watercourses (COWs) in the Borough; • Significant brownfield redevelopment and regeneration planned within the urban areas of Pendle Borough and potential new development of adjacent greenfield areas (see Section 2). As the principle aim of the Sequential Test is to locate development in the lowest flood risk zone, the Pendle SFRA emphasises the steering of planned development to zone 1 which is appropriate for all categories of land use vulnerability. Where no suitable alternative is available, there may be some scope for locating development in higher risk flood zones depending on the vulnerability of the proposed land use. Table 4.2 shows the PPS 25 criteria with respect to the vulnerability of planned development in Pendle Borough and appropriate levels of flood risk; Appendix B gives the full details of acceptable land uses for these vulnerability classifications. Regardless of vulnerability, PPS 25 indicates that development proposed in zones 2 and 3 must demonstrate there is no reasonable alternative available in a lower flood risk zone. In addition, all major6 developments must meet other requirements (such as managing surface water runoff to ensure no adverse effect on flood risk elsewhere) through a detailed FRA that meets the requirements of PPS 25.

Table 4.2 Location of Planned Development According to Vulnerability

Planned Development Zone 1 Zone 2 Zone 3a Zone 3b Low Medium High Functional Floodplain Probability Probability Probability

‘Highly vulnerable’ residential Yes Yes, if Exception No No development Test is passed

‘More vulnerable’ residential Yes Yes Yes, if Exception No development Test is passed Business use development Yes Yes Yes No (‘less vulnerable’) Water Compatible Infrastructure Yes Yes Yes Yes, if ‘essential infrastructure’ (‘essential Infrastructure’) and Exception Test is passed

6 According to PPS 25,“a major development is one in which the number of dwellings to be constructed is 10 or more, or the site area is equal to or greater than 0.5 ha. Non-residential developments are defined as major if they involve a floor space equal to or greater than 1 000 m2, or a site area greater than 1 ha.”

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The bulk of planned residential development in Pendle Borough will come under the ‘more vulnerable’ land use classification, with possible exceptions including residential development/ institutions for the elderly or very young which are classified as ‘highly vulnerable’. Most development for business use will come under the ‘less vulnerable’ classification. To inform the LDF and the strategic planning process, the primary (fluvial) flood risk of the potential development areas was assessed using the Environment Agency’s flood zones. In addition, flooding from secondary sources was also considered using a variety of information sources including historical records, Ordnance Survey maps and site visits. The SFRA has focussed on characterising flood risk (including non-fluvial sources) throughout the Borough and the areas in which future development is planned. This has been undertaken to produce an SFRA tailored to best inform the LDF with respect to the detailed planning of future redevelopment and regeneration in Pendle Borough, and to provide a guide to local flood risk issues which will then inform the FRAs of areas selected for development.

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5. Flood Risk in Pendle Borough

5.1 Introduction An SFRA is the key source of information on local flood risk for a LPA, used to inform strategic planning decisions in the LDF, as well as provide Development Control with sufficient information to determine planning applications. To provide a comprehensive overview, flood risk throughout the Borough has been characterised based on all available sources of information. This includes consideration of both primary, fluvial sources of flooding, as well as other secondary sources of flooding. This has been largely based on the Environment Agency’s flood zones (see Box 5.1) combined with historical flood records from Pendle Borough Council, the Environment Agency and sewerage companies to capture information on secondary sources of flooding where available. The SFRA thus provides an indication of the varied nature of flood risk throughout the Borough, which will both inform planning decisions and guide the focus of more detailed FRAs of proposed developments.

Box 5.1 The Environment Agency’s Flood Map

In 2004, the Environment Agency published their Flood Map comprising two key components, a Historic Flood Map and Flood Zones. The Historic Flood Map depicts the maximum extent of all observed fluvial and tidal flood events where sufficient information is available to derive the extent. This can be based on a range of information sources, including aerial photography, flood surveys, questionnaires, interviews etc.

The Flood Zones are not limited to areas where flooding has previously occurred and been recorded, and instead depict the level of risk due to flooding from rivers and the sea. The zones reflect the risk categories in PPS 25 to enable planning authorities to apply the sequential test for planned development. With respect to fluvial flooding, the zones are defined as follows:

• Zone 1 Low Probability: Less than 0.1% chance (1 in 1 000) of flooding in any year;

• Zone 2 Medium Probability: Greater than 0.1% (1 in 1 000) but less than 1% (1 in 100) chance of flooding in any year;

• Zone 3 High Probability: Greater than 1% (1 in 100) chance of flooding in any year.

The flood zones are based on a Digital Terrain Model (DTM) derived from aerial survey and flow estimates from the Flood Estimation Handbook (FEH). JFLOW, a two-dimensional raster floodplain model was used to generate the flood outlines for all catchments over 3 km2. It is important to note that the flood outlines do not account for structures in the floodplain such as defences, bridges, culverts and embankments which may have significant local effects on the flood zones.

The flood zones were produced as a national exercise and therefore provide a broad indication of fluvial flood risk within the above constraints. In some areas, where more detailed modelling to an appropriate methodology has produced more refined flood zones, these have been used to replace the zones derived nationally using JFLOW.

The Environment Agency continuously updates both the Historic Flood Map and the Flood Zones as more information on actual flood events and detailed modelling becomes available.

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5.2 Historical Flooding

5.2.1 Environment Agency Historical Flood Map Like much of the country, there have been many incidents of flooding in Pendle Borough dating back many years, in different locations and from different sources and types of events. Sufficient information has been compiled from some of the more recent fluvial flood events to enable the Environment Agency to derive extents of flooding for the Historical Flood Map (see Box 5.1). Figures 5.1 to 5.3 show the historical extents for the January 1992 flooding in Lomeshaye, and the June 2000 flooding in Barrowford and Walverden respectively.

5.2.2 Other Records of Flooding In addition to these events, there are numerous other records of flooding that relate to some older and/ or more localised events for which extents have not been mapped. Table 5.1 lists historical records of flooding in Pendle Borough identified from various sources of information including the Ribble and Aire CFMPs, the Burnley, Nelson and Colne Flood Risk Management Strategy, as well as some additional records held by Pendle Borough Council and obtained from newspaper articles. This list should not be considered exhaustive, but is useful for indicating the locations and types of flooding that have historically occurred throughout the Borough.

Table 5.1 Historical Flood Records in Pendle Borough

Year Location Event Details

December 1837 Barrowford Bridge swept away by floods

November 1866 Ribble and Aire Severe flooding from Pendle and Colne Water catchments

September 1877 Barrowford Flooding from Pendle and Colne Water

July 1881 Barley to Barrowford Flooding from Pendle Water due to summer convection storm on Pendle Hill

Gisburn Road “like a river”

(Colne Water not affected)

February 1920 Barrowford Flooding from Pendle and Colne Water

Lomeshaye area badly flooded

1927 Trawden Flooding in Rock Lane to 1.5 metres

July 1932 Barnoldswick 13.5 cm of rainfall in Barnoldswick

Major flood damage to Bancroft Mill and in Walmsgate

Gillians Lane and other roads severely eroded by surface water

Ouzledale foundry destroyed by lightening and flood

1946 Barrowford No further details

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Table 5.1 (continued) Historical Flood Records in Pendle Borough

Year Location Event Details

March 1947 Aire catchment Snowmelt on frozen ground

Cottontree and Properties undercut due to flooding from Colne Water Trawden

1952 Barrowford No further details

1964 Barrowford No further details

1965 Earby Flash flooding

August 1967 Barrowford Major flooding in Gisburn Road area “most severe to date”

Possibly Trawden

October 1967 Earby Flooding of roads

April 1970 Aire tributaries Severe flooding

1987 Barnoldswick No further details

1991 Barrowford Pendle Water

January 1992 Barrowford Flooding of Nelson and Colne College, Reedyford Bridge, 26 properties, Lomeshaye Industrial Estate

2000 Barrowford Flooding of Nelson and Colne College, Reedyford Bridge, 6 properties

February 2000 Barnoldswick Flooding in Ghyll Meadows due to insufficient culvert capacity

March 2000 Nelson Flooding in Brunswick Street from Walverden Water

June 2000 Barrowford Flooding of 12 properties to 0.3 metres, Lima Engineering (just downstream of Walverden Water confluence) to 0.6 metres, Benefits Agency nearly flooded

Trawden Flooding of 3 properties to between 0.3 and 1 metre

October 2000 Barnoldswick Flooding in Ghyll Meadow, Greenber Field Lane and Picard Close

Rolls-Royce factory closed – Crowsnest Syke

November 2000 Barrowford Flooding in Sandy Lane, Pendle Street, Wilkinson Street, Gisburn Road, Calder Vale, Lougher Clough Street due to high levels in Pendle Water and flow backing up and surcharging from Wilkinson Street culvert

Also reference to a blocked trash screen

September 2001 Colne Flash flooding of Vivary Mill due to heavy rainfall exceeding capacity of the culverted North Valley Stream and surcharging into factory grounds

October 2001 Trawden Flooding of 14 properties

December 2001 Barrowford Pendle Water overtopped defences just upstream of Lomeshaye

23 residences and 7 industrial premises were inundated by up to 0.75m of water

February 2002 Earby Flooding from Earby Beck

June 2002 Barnoldswick Flash flooding of Gisburn Road, Westfield Mill

Also reference to flooding 4 times in 3 years

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Table 5.1 (continued) Historical Flood Records in Pendle Borough

Year Location Event Details

August 2002 Earby Flooding of roads, residents trapped in houses due to summer convection storm

August 2004 Earby Flash flooding of roads due to summer convection storm

Trawden Flooding of Burnley and Colne Roads

April 2006 Earby Flooding in Wentcliffe Drive due to runoff from construction site

Based on the compiled records, it can be observed that, in addition to prolonged winter rainfall events which tend to cause extensive flooding in valley-bottom floodplains, heavy summer thunderstorms have also caused localised ‘flash’ flooding on a number of occasions. This includes the flooding from Barley to Barrowford in July 1881, Barnoldswick in July 1932, Colne in September 2001, and the recent flooding in Earby. This type of flooding can be exacerbated by areas of steep topography in the catchments and settlements adjacent to the upper reaches of river systems with limited floodplains. The records also provide a useful indication of areas that are particularly problematic with respect to flooding. For example, the Burnley, Nelson and Colne Flood Risk Management Strategy reported that there have been 21 flood events in Barrowford in the last 130 years (note not all appear in the above table). Table 5.1 shows an apparent increase in more recent records of flooding, which could be attributed to a number of reasons including:

• Improved recording or reporting of flood events; • Possible increase in frequency of flood events;

• Historic encroachment of the floodplain;

• A greater sensitivity of the present built environment to flooding; and/ or

• An increase in the value of properties and possessions at risk. These historical records of flooding provide a useful indication of the type and frequency of flood events that are known to have occurred in the Borough. It should be noted however that these events are indicative only and can only be used to characterise flood risk. They do not present a comprehensive record of, or absolute guide to, flood risk. The events represent particular rainfall and antecedent hydrological conditions. More extreme events, or changes in land use and climate, could have more extensive or different impacts.

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5.3 Fluvial Flood Risk As indicated by the historical records of flooding, the primary source of flood risk in Pendle Borough is due to flooding associated with watercourses (i.e. fluvial flooding). Throughout the Borough, watercourses pose a potential flood risk to both existing and future development, particularly the encroachment of the floodplain by Victorian-era mills and factories (in Colne and Trawden), residential development (in Barrowford) and more recent factories and warehouses (in Lomeshaye). This development constricts Pendle and Colne Waters as they pass through Colne, Barrowford, Nelson and Lomeshaye with significant development lying in the natural floodplain that the rivers would formerly have occupied during periods of high flow.

5.3.1 Watercourses Watercourses in Pendle Borough fall into three main catchments; watercourses draining to the Calder in the south, to the Ribble in the northwest and to the Aire in the northeast (see Figure 5.2). Tables 5.2 to 5.4 list watercourses identified in the Borough for the Calder, Ribble and Aire catchments respectively (Watercourses in brackets are smaller tributaries that do not appear in Figure 5.2.). The watercourses identified include both main rivers (including former critical ordinary watercourses, or COWs) and ordinary watercourses (OWs). Box 5.2 describes the recent national enmainment process that transferred responsibility for COWs from LPAs to the Environment Agency.

Table 5.2 Watercourses in Pendle Borough (Calder Catchment)

Watercourse Status Respons- Description ibility (Source, Location, Geology, Hydrology etc)

Pendle Water Main EA Steep eastern slopes of Pendle Hill, above Barley, flows river initially southeast, and then southwest after confluence with Colne Water. Upper catchment Pendle grit, shale and limestone, with coal measures and limestone in the valley floors. Cover of hill peat on Pendle Hill with a boulder clay drift covering the lower catchment. Catchment responds rapidly to rainfall events. Includes Black Moss and Ogden Reservoirs.

Colne Water Main EA Collects flow from several steep becks in the southeast of river Pendle Borough, flows west to confluence with Pendle Water. Catchment mainly shale with boulder clay drift. Tributaries likely to respond rapidly to rainfall events.

Tributaries of Pendle Water

Walverden Water Main PBC Walverden Water source on west side of Boulsworth Hill, Hendon Brook river/ flows west to Pendle Water. Catchment mainly grit and Catlow Beck OWs coal measures, with boulder clay drift. Rapid response to rainfall. Long sections of culverting. Walverden Water (Clough Head Beck) and the Hendon Brook COW (now enmained) flow through Bradley AAP.

Edge End Brook Main EA/ PBC Lower reach was a COW (now enmained). Small river/ watercourse, flowing from Little Marsden. Culverted under OW M65 and Lomeshaye Industrial Estate.

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Table 5.2 (continued) Watercourses in Pendle Borough (Calder Catchment)

Watercourse Status Respons- Description ibility (Source, Location, Geology, Hydrology etc)

Hollin Mill watercourse Main EA/ PBC Lower reaches of both were COWs and are now Sefton Street watercourse rivers/ enmained. Small watercourses issuing near Brierfield OWs with urbanised catchments. Culverted under Brierfield, flowing northwest into Pendle Water.

(Spurn Clough, Moor Isles OWs Landowner/ Small, steep watercourses draining around Higham and Clough, Fir Trees Brook, PBC Fence, in the west of the Borough. Rural catchment, Acres Brook, Old Laund mainly grit and coal measures, with boulder clay drift. Clough)

Clough Springs Main EA/ PBC Lower reaches were COWs (now enmained). Small rivers/ tributaries of Pendle Water with culverted sections. (Two unnamed watercourses OWs near Lomeshaye Industrial Estate north and Carr Hall)

Tributaries of Colne Water

Wanless Water OW Landowner/ Watercourse impounded in Foulridge reservoirs. Issues PBC below Kelbrook Moor, flows southwest. Catchment mainly grits with boulder clay drift.

(Sykes Beck, High Laith Beck, OWs Landowner/ Northern tributaries of Colne Water. Rural catchment, grit Shawhead Beck) PBC and coal measures with boulder clay drift.

River Laneshaw OWs Landowner/ Eastern headwaters of Colne Water. Rural, steep PBC catchments including Laneshaw Reservoir, predominantly (Monkroyd Beck, Hullown grit and coal measures with boulder clay and hill peat drift. Beck) Catchments likely to respond rapidly to rainfall events.

Wycoller Beck OWs Landowner/ South eastern headwaters of Colne Water. Steep PBC catchments including the village of Wycoller, (Smithy Clough, Turnhole predominantly grit and coal measures with boulder clay Clough, Deep Beck Clough) and hill peat drift. Large area of upper slopes with many tributaries draining into one main channel. Catchments likely to respond rapidly to rainfall events.

Trawden Beck Main EA/ PBC Main river downstream of Trawden. Source on northwest Beardshaw Beck river/ side of Boulsworth Hill above Trawden. Steep gradient, OWs flows north to Colne Water. Catchments mainly shale, (Broad Green Beck) coal measures and grit, with boulder clay drift in the lower catchment and hill peat on Boulsworth Hill. Large area of upper slopes with many tributaries draining into one main channel. Catchments likely to respond rapidly to rainfall events.

(Church Clough Beck) OW Landowner/ Short, steep tributary of Colne Water. South of Colne, PBC located in South Valley HMR area. Catchment mainly grit and coal measures, with boulder clay drift. Catchment likely to respond rapidly to rainfall events.

Primet Bridge Main EA/ PBC Lower reach of both were COWs (now enmained). Small Swindon Clough rivers/ watercourses, issuing from hills south of Colne and OWs Nelson. Culverted beneath Whitewalls Industrial Estate.

North Valley Stream Main EA Culverted watercourse formerly a COW (now enmained). river Flows through Colne, roughly parallel to Vivary Way, North Valley Road and Windsor Street. Joins Colne Water near Primet Bridge.

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Table 5.2 (continued) Watercourses in Pendle Borough (Calder Catchment)

Watercourse Status Respons- Description ibility (Source, Location, Geology, Hydrology etc)

Tributaries of River Calder

Sabden Brook OW Landowner/ Upper reaches below Pendle Hill. Rural catchment, PBC mainly grit with boulder clay drift.

Table 5.3 Watercourses in Pendle Borough (Ribble Catchment)

Watercourse Status Respons- Description ibility (Source, Location, Geology, Hydrology etc)

Stock Beck Main EA/ PBC Lower reach in and below Barnoldswick was a COW (now river/ enmained). Large catchment area in northwest of OW Borough, mainly shale, grit and sandstone with boulder clay drift in lower catchment. Catchment responds rapidly to rainfall events.

Crowsnest Syke OW PBC Small watercourses in and around Barnoldswick. Parts culverted, many sinks and issues. (Unnamed watercourse near Barnoldswick)

Upper Stock Beck OW Landowner/ Small watercourses upstream of Barnoldswick. Gillians Beck PBC Catchments mainly shale, grit and sandstone with boulder clay drift in lower catchment. Steep watercourses draining (Near Weets Hollow, Weets a large area of the upper slopes of Weets Hill with many Hollow, Weets Tongue, tributaries draining into these two main channels down Mosses Lee Clough, Moor into Barnoldswick. Catchments likely to respond rapidly to Side Beck) rainfall events.

Fools Syke OW Landowner/ Small watercourses draining north from Weets Hill. Rural PBC catchments, mainly shale, grit and sandstone with boulder (Horrox Gill, Coverdale clay drift in lower catchment. Steep watercourses draining Clough, Higher Clough) a large area of the upper slopes draining into the one main channel. Enters Stock Beck downstream (north) of Barnoldswick. Catchments likely to respond quickly to rainfall.

Flush Beck OW Landowner/ Watercourses around Bracewell in the north of Pendle Bottom Beck PBC Borough. Rural catchments with relatively low stream gradient, mainly shale with some limestone, covered with (Lodge Hill Syke, Wedacre a boulder clay drift. Syke, Old Park Syke, Hesketh Rough Syke, Hell Forest Syke)

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Table 5.4 Watercourses in Pendle Borough (Aire Catchment)

Watercourse Status Respons- Description ibility (Source, Location, Geology, Hydrology etc)

Earby Beck Main EA / PBC Watercourse in northeast of Pendle Borough with large New Cut river/ (parts catchment area. Catchments mainly grit, sandstone and OW formerly shale with boulder clay and peat. Alluvium and alluvial fan (Clough Hole) ESIDB) deposits in valley. New Cut is an artificial straightened channel (now enmained) formerly an OW maintained by ESIDB. Large valley floor area with low gradient and poorly drained.

Salterforth Beck OW ESIDB Small watercourse draining through Salterforth. Geology as for Earby Beck. (Carr Dyke)

Kelbrook Beck Main EA/ PBC/ Lower reach was COW (now enmained). Steep river / Landowner watercourse draining west down from Kelbrook Moor. OW Catchment mainly grit, shale and coal measures covered by some boulder clay drift, likely to respond rapidly to rainfall events.

Wentcliffe Beck OW PBC/ Steep watercourse draining west down from Thornton Hodge Syke Landowner Moor. Catchments mainly grit, shale and coal measures covered by some boulder clay drift, likely to respond rapidly to rainfall events.

County Brook OW PBC/ Southern headwaters of Earby Beck. Small steep ESIDB/ watercourses, drain in a crescent around from Whitemoor (Wanless Beck, Whinberry Landowner via Foulridge around to Kelbrook Moor. Catchments Clough, Fold Beck, mainly grit and coal measures covered by some boulder Lancashire Gill, Cinder Hills clay and alluvium drift, likely to respond rapidly to rainfall Clough) events.

(Unnamed watercourses in OW ESIDB/ Small watercourses, mainly field drains and straightened, lower Earby Beck catchment) Landowner lower reaches of hillside becks.

(Gill Clough, Gill Syke) OW PBC / Small, low-gradient watercourse between Barnoldswick ESIDB/ and Earby. Rural catchment with similar geology to Earby Landowner Beck.

Box 5.2 Enmainment of COWs

Historically, the Environment Agency has been responsible for main rivers, whilst LPAs (and IDBs) have been responsible for the management of most ordinary watercourses. As part of a national response to the extensive floods that occurred in 1998, the Environment Agency introduced the new designation of ‘critical’ ordinary watercourses (COWs). These watercourses are those considered to pose the greatest flood risk to people and property. This was based on watercourses with 25 or more properties at flood risk per kilometre stretch (and, to provide continuity of management along reaches, any reach of ordinary watercourse downstream from a COW to the main river). COWs were identified by the Environment Agency at a regional level, and in Pendle Borough nine watercourses were designated as COWs (see Tables 5.2 to 5.4 and Figure 5.4).

In 2003, DEFRA announced that all COWs were to be designated main river, thereby transferring responsibility for these watercourses to the Environment Agency. The aim of this enmainment process was to give one Competent Authority responsibility to better manage flood risks. Enmainment was completed in 2006 and the former COWs in Pendle Borough are now designated main river and fall under the responsibility of the Environment Agency.

For the first year after enmainment, the Environment Agency was required to contract back to local authorities (where willing and able) the maintenance of COWs and update of the NFCDD (see Section 5.5.4) to include information on the COWs. This arrangement is reviewed yearly, so the future responsibilities of Pendle Borough Council with respect to these former COWs are not certain.

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Box 5.2 (continued) Enmainment of COWs

The implications of the enmainment process for development relates primarily to the Environment Agency’s policies for main rivers, in particular with respect to easements and culverting, which will now extend to the recently enmained COWs. In the case of development on greenfield land, an easement of 7 to 10 metres is required on either side of main rivers, and a betterment is sought on previously inaccessible brownfield frontages on a pragmatic basis. Easement widths for ordinary watercourses (which previously included the COWs) are governed by local bye-laws. The 7 Environment Agency recommendation on ordinary watercourses is for easements of 3 or 5 metres on either side 8 depending on the size of the watercourse. The Agency also has a presumption against culverting of main river, and will generally seek for the restoration of culverted sections back to open channel wherever practical with a view to reducing flood risk associated with blockages or capacity exceedance. Both these easement and culverting policies now apply to the recently-enmained COWs and must be taken into account wherever development is proposed adjacent to main rivers (including the former COWs).

5.3.2 Environment Agency’s Flood Zones In order to provide an indication of the flood risk posed by watercourses, the Environment Agency has derived flood zones that depict the level of risk. Figure 5.5 shows the extent of the fluvial flood zones within Pendle Borough. As noted in Box 5.1 however, these zones provide a broad indication of fluvial flood risk only and have only been produced for catchments greater than 3 km2. Where development is proposed in, or near the boundaries of, the higher risk flood zones (i.e. zones 2 and 3), more detailed hydraulic modelling and topographic survey may be required at the FRA stage to determine the floodplain extent and design flood levels more accurately. This also provides a means for investigating the effects of climate change on flood risk, an important aspect of the FRA for proposed development. Table 5.5 below summarises areas where the Environment Agency has developed more detailed hydraulic models of watercourses in the Borough. Pendle Borough Council does not hold any models of former COWs or ordinary watercourses, and no other models of watercourses in the Borough have been identified. Figure 5.6 shows output from the modelled reaches of the Calder catchment indicating the extent of flooding for a range of design flood events from the 1 in 5 year to 1 in 100 year events. Figure 5.7 shows the modelled reaches of the Aire catchment and indicates some of the key findings of the modelling study.

7 Ordinary Watercourses - Land Drainage Act (1991) Consent: http://www.pipernetworking.com/floodrisk/b25lda1991.html 8 Environment Agency – Policy Regarding Culverts: http://www.pipernetworking.com/floodrisk/culvert1.pdf

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Table 5.5 Environment Agency Hydraulic Models

Catchment Watercourses Date Model Details

Calder Pendle Water, Colne Water, Trawden Brook and 2001 ISIS model developed by JBA under the unnamed watercourse in Barrowford Section 105 modelling framework

Aire Earby Beck, New Cut, Kelbrook Beck (lower) 2005 ISIS model developed by Atkins under and Salterforth Beck (part) the Section 105 modelling framework

It may be possible to utilise these models for more detailed investigations at the FRA stage subject to agreement with the model owner/ relevant authority. Where there is no existing model, it may be necessary to develop a model of the watercourse to assess the fluvial flood risk to a proposed development more accurately. Finally, it must be noted that the Environment Agency flood zones do not provide any indication of flood risk due to secondary sources of flooding including culvert blockage, sewer and overland flow. These other flood risks have been characterised for Pendle Borough as part of this SFRA and identified at a local level for the potential development areas. They too must be considered and addressed in further detail at the FRA stage of proposed development.

5.4 Secondary Sources of Flood Risk The collation of historical records and other information on flood risk in the Borough highlighted that, in addition to flooding from watercourses, other mechanisms of flooding can pose significant risks to development. These secondary sources of flood risk include surface runoff from hillsides, flooding from sewers and drains, and blockages to artificial drainage systems (such as ditches and culverts). PPS 25 also emphasises the need to consider these other sources of flooding both at the strategic and site level when planning development.

5.4.1 Blocked or Insufficient Drainage Structures Where watercourses have been enclosed there can be potential for blockage and/or insufficient conveyance of peak flows. Flooding can occur due to subsequent backing up of culverts or bridges so that water overflows the channel and follows the lowest topography overland. Collapsed culverts, fallen trees and other debris are common causes of blockages, whilst constrictive culverts or bridges and other structures can trap debris. Improperly designed trash screens at culvert entrances can exacerbate the risk of flooding. Where a specific problem exists, there may be scope to reduce the risk by increasing culvert capacity, removing obstructions and redesigning trash screens to aid conveyance of peak flood flows. Regular maintenance also minimises the potential for blockages to occur.

Ditches, culverts and other drainage structures appear to have been related to a number of incidents of flooding in Pendle Borough. Reports indicate that limited capacities of culverts and channels have caused or exacerbated flooding on a number of occasions in Earby, Barnoldswick and beneath Walverden Water Reservoir in Newbridge. Currently there is limited information available on the former COWs and other culverts in the Borough, however the Council have an ongoing program to assess and improve structures across the Borough, both for ordinary watercourses and on behalf of the Environment Agency, for the now-enmained COWs.

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5.4.2 Sewer Sewage and surface water drains pose a potential flood risk to property and future development through a number of mechanisms. If storm water flows exceed the capacity of the network, water can pond or flow above ground rather than draining via sewers, potentially inundating property. Where surface water outfalls are not fitted with flap valves, there is also a risk of backflow when river levels are high. Blockages in the sewerage network can have a similar effect, indeed sewer flooding can occur outside of meteorological flood events. In addition to considering the risks of sewer flooding on planned development, the effects of the development and the resultant increase in sewage flows and surface water runoff must be considered. If not appropriately managed, development could increase the risk of sewer flooding both to the development itself as well as downstream areas. United Utilities and Yorkshire Water are the water companies responsible for public sewers (i.e. adopted sewers) for foul, combined and surface water drainage in Pendle Borough. Private sewers are the responsibility of the owners. They have been consulted to identify areas at risk of sewer flooding in the Borough. Both maintain a database of flood incidents associated with the sewerage network however, as works are carried out to resolve flooding problems, the relevant entries are removed from the database. Appendix C contains details of the current known risk areas for sewage flood incidents, whilst Appendix D contains details of the current known risk areas for surface water gullies maintained by Pendle Borough Council. This list will change as upgrading and repair works are carried out, and as new incidents are reported. Furthermore, it does not present a definitive guide to sewer flood risk in the Borough as different areas may be at risk under different meteorological conditions, and new areas may be at risk from the effects of future urbanisation and/ or due to climate change. Nonetheless, these records highlight the importance of considering sewer flooding when planning new development, and give an indication of current known problem areas. Where development is planned, early consultation with the relevant water company is necessary to identify potential risks to the development or issues associated with the additional load on the sewerage infrastructure, so that sewer flood risk can be appropriately managed.

5.4.3 Overland Flow Overland flow is water flowing over the ground surface that has not entered a natural or artificial drainage system. Overland flow flooding is sometimes also referred to as pluvial flooding or surface water runoff flooding. When the infiltration capacity of land is exceeded, excess rainwater flows overland; this water will collect in topographic depressions and at obstructions, and can inundate development downslope. Severe rainfall events, steep slopes, soils, geology and land management all contribute to and affect the severity of overland flow. Areas with large upslope catchments will be particularly prone. Figure 5.8 provides an indication of topography in the Borough based on available LIDAR data. Large areas of the Borough are overlain by pleistocene boulder clay drift. Alluvium occupies narrow strips along the valleys of Pendle and Colne Waters, and Stock and Earby Becks. The steep slopes midway up the catchments tend to be without drift, whilst the upper hilltops are covered by hill peat drift. These extensive areas of clay and the undulating topography mean catchments throughout the Borough tend to respond quickly to rainfall events (i.e. there is a tendency for rainfall to runoff as overland flow rather than infiltrating into the ground) and may pose a risk of overland flow flooding.

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Different areas may experience problems with overland flow under different rainfall severities and patterns, antecedent conditions and land use. In particular, new development on greenfield land can exacerbate risk through increased runoff and changes to natural drainage. When planning new development, there must be consideration not only of the flood risk from overland flow to the development itself, but also the risk that the development poses to areas downslope.

5.4.4 Canal Canals can pose a flood risk via a number of different mechanisms, including the culverting of watercourses beneath the canal (which raises the risks outlined in Section 5.4.1), obstruction to overland or floodplain flow along embankments, operational malfunction, the potential to convey floodwater between catchments, and embankment failure. The Leeds and Liverpool Canal passes approximately from the southwest to the northeast of Pendle Borough, following Pendle Water then up to Foulridge and Earby Beck. Many small watercourses are culverted underneath the canal, or enter and exit the canal via sluices. The flood zones (see Figure 5.5) show that south of Foulridge, the Wanless Water floodplain crosses the Leeds and Liverpool Canal where it exits the Foulridge Tunnel. This could be an area where the canal has the potential to pose a risk of flooding through the transfer of floodwaters from the watercourse to the canal. One known incident of flooding associated with the canal has been identified. Flooding of a road and several properties was reported in Salterforth due to the malfunction of an overflow sluice in 2002. Incidents such as this highlight the need to consider the flood risk implications of the canal for development planned in the Borough.

5.4.5 Groundwater Raised groundwater levels caused by prolonged periods of rainfall can result in flooding. New springs may appear in locations previously thought to be above the water table. Once groundwater flooding occurs, it may take a long time for groundwater levels to fall and flooding to abate. The geology of the Borough is varied, consisting of coal measures, grits, limestone, sandstone and shale. There is also a complex system of (dormant) faults and therefore the geology can vary over relatively short distances. The associated changes in permeabilities correlate with the frequency of ‘issues’ and ‘sinks’ indicated on the Ordnance Survey maps for small watercourses in the upper headwaters. The majority of the catchment is classified as a negligibly permeable non-aquifer9 representing minor aquifers with varying permeabilities. Soils have either high or low leaching potentials; in particular the boulder clay drift tends to have a low permeability. Soil permeability also affects the use of SuDS in new developments to manage runoff (see Sections 5.4.3 and 7.2.2) since infiltration-based measures (e.g. soakaways) will only be feasible in areas where the soils have sufficient permeability.

9 Groundwater Vulnerability 1:100 000 Map Series, Sheets 10 Central Lancashire and 11 South Pennines, Environment Agency.

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No incidents specifically attributed to groundwater flooding have been identified in Pendle Borough to date. In June 2000, cellar flooding occurred in Newbridge, Barrowford however this appears to be due to surface water entering cellars rather than groundwater. Despite this, there remains a minor risk that should be considered when planning new development, particularly in areas where there are existing springs or the potential for new springs to emerge as a result of excess rainfall and elevated groundwater levels.

5.4.6 Infrastructure Failure Where infrastructure exists that retains, transmits or controls the flow of water, flooding may result if there is a structural, hydraulic, geotechnical, mechanical or operational failure. The main infrastructure in Pendle Borough are the numerous reservoirs associated with the Leeds and Liverpool Canal and public water supply, as well as the canal itself. For large storage structures such as reservoirs and detention dams, the Reservoirs Act 1975 requires the regular inspection by a panel engineer of all water-retaining structures over 25 000 m3. Provided these inspections are carried out regularly and thoroughly, and any recommendations implemented, the likelihood of a catastrophic breach can be considered minimal. On 1 October 2004, the Environment Agency took over the role of Enforcement Authority under the 1975 Reservoirs Act, responsible for the regulation and enforcement for all 2000 reservoirs under the Act in England and Wales. One of their tasks will be to introduce Flood Plans, as required by the Water Act 2003 for specified reservoirs. DEFRA has issued guidance for undertaking Flood Plans which is currently in consultation draft10. The guidance specifies that Flood Plans should include an assessment of the potential consequences of failure in terms of both the extent of inundation and the likely loss-of-life, on-site activities by the Undertaker, and the essential communication with the Emergency Services. The impact assessment should include a ‘Standard Analysis Scenario’ based on a ‘rainy day’ (1 in 10 000 year extreme rainfall event) dam break flood for a full reservoir. Outputs of the impact assessment should include maps showing the outer limit of inundation, as well as the ‘population at risk’, where flooding exceeds specified criteria based on depth and velocity. As they are developed, Flood Plans will provide an important source of information for both development and emergency planning. LPAs should consult with the reservoir undertakers and Flood Plan to identify areas at risk of rapid inundation in the event of a catastrophic reservoir failure. These areas will need to be taken into account in the development planning process as there would be difficulties evacuating in such an event and therefore a risk to life.

5.5 Flood Risk Management Flood risk in the UK is managed at different levels by a number of authorities. At a national level, DEFRA’s emerging strategy for overall flood risk management in the UK is Making Space for Water, which takes a holistic approach to management of risk from all forms of flooding, seeking to ensure the programme helps deliver sustainable development. The Environment Agency also manages flood risk at a national scale, including the development of the Flood Map (see Box 5.1) and National Fluvial and Coastal Defence Database (NFCDD)

10 Engineering Guide to Emergency Planning for UK Reservoirs, DEFRA, June 2006.

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(see Section 5.5.4). In addition, it addresses flood risk at a catchment scale, through the development of Catchment Flood Management Plans (CFMPs), and at a sub-catchment scale, through the development of flood risk management strategies for specific reaches or areas. The LPA and water companies then tend to address flood risk management at a more local level, through their management and maintenance of local natural and artificial drainage systems. The following sections summarise key flood risk management documents relevant in Pendle Borough.

5.5.1 Regional Flood Risk Assessment The Environment Agency is currently preparing a Regional Flood Risk Assessment (RFRA) for the North West in consultation with the North West Regional Assembly as an integral part of the Regional Spatial Strategy (RSS) (see Section 3.3.2). PPS 25 outlines the need to develop RFRAs informed by Catchment Flood Management Plans (CFMPs) as well as River Basin Management Plans (RBMPs) 11 and Shoreline Management Plans (SMPs). The North West RFRA will seek to ensure the policies in the relevant documents are implemented and followed. RFRAs identify flood risk on a broad scale by considering potential risk in terms of population, flood zones and likely future population growth. In comparison to other LPAs in the North West, the Environment Agency has indicated that Pendle Borough ranks approximately mid- range in terms of key indicators of flood risk. This SFRA has been developed in line with the broader objectives of the emerging North West RFRA.

5.5.2 Ribble and Aire Catchment Flood Management Plans The objective of Catchment Flood Management Plans (CFMPs) is to consider flood risk management at a broad scale, taking into account scenarios for future changes in land use, land management and climate. The plans aim to promote complementary policies that ensure sustainable, catchment-wide management of flood risk over the next 50 to 100 years. Two CFMPs cover Pendle Borough; the Ribble CFMP covers the majority of the Borough including the Ribble and Calder sub-catchments identified in Figure 5.4, whilst the Aire CFMP covers the northeast (including Earby, Kelbrook and Salterforth). Both of these CFMPs are currently at the scoping stage and are due to be completed imminently.

Ribble CFMP The Ribble catchment extends from Settle in the north to Lytham St Annes in the west, with most of Pendle Borough falling in the Ribble CFMP’s south eastern area. The Ribble CFMP identifies Barrowford in particular as one of the major regional areas at risk. It also notes that the urban corridor along Colne and Pendle Waters in zone 2 (i.e. the 0.1%, or 1 in 1 000 year, floodplain) includes a relatively high concentration of areas with high social vulnerability. Climate change, which may see winter rainfall increase by 10% to 20% and more intense summer and winter rainfall events, is identified as one of the most important future factors in managing flood risk.

11 RBMPs are part of the implementation of the European Union’s Water Framework Directive. The Ribble RBMP, which will cover a large area of Pendle Borough, will be completed in 2007.

Aire CFMP The Aire catchment extends from Gargrave to Goole. The Earby Beck catchment comprises part of the catchment of one of the larger Aire tributaries, however the Aire CFMP tends to concentrate on flood risk in the larger urban areas (with greater population at risk) downstream along the Aire and outside of the Borough boundary.

Constraints and Opportunities for Flood Risk Management A number of constraints and opportunities have been identified with respect to the flood risk management options under consideration in the emerging Ribble and Aire CFMPs: • Attenuation and retention: SuDS are endorsed to prevent increases in runoff, however it is noted that their use can be complicated by issues relating to high groundwater levels, ground contamination and adoption. Within the Borough, washland creation is not seen as a feasible option due to land availability constraints, and there is limited capacity for utilising existing reservoirs for flood storage; • Rural land use change: Much of the habitat of the South Pennine Moors SPA/ SAC located to the south of Nelson is classified as being in ‘unfavourable condition’. The removal of moorland gripping has been identified as a way of improving the habitat, which could also have a positive effect on flood risk through an associated reduction in runoff; • Increased conveyance: Improvements to channel conveyance, constrictive structures and structures with potential for blockage were identified as possible options for reducing and managing flood risks, together with public education on the impacts of fly tipping; • Localised protection measures: It is noted that the costs associated with provision of new defences and continued maintenance of existing defences are considerable. In addition, defences may have adverse effects on ecology and landscape;

• Influencing and informing: The use of strategic development planning to manage flood risk is of particular relevance to SFRAs. The preference to locate new development in zone 1 (low probability of flooding) is reiterated. This can conflict with other sustainable objectives such as the preference for redevelopment of brownfield sites where they are located in the floodplain, requiring careful planning and design to reduce flood risks to an acceptable level;

• Monitoring, surveys and research: The gathering of more data to gain a better understanding of flood risk is identified as an option that takes time, but can lead to more appropriate and sustainable responses to managing the risks; • The options identified at the scoping stage of the CFMP process will be taken forward for further consideration. The CFMPs will then consider which are most pragmatic and feasible for each part of the catchment. In the south of the Borough, the Burnley, Nelson and Colne Flood Risk Management Strategy has already progressed the investigation and programming of some of these measures.

5.5.3 Burnley, Nelson and Colne Flood Risk Management Strategy The Burnley, Nelson and Colne Flood Risk Management: Draft Strategy for Consultation (the ‘BNC Strategy’) was published in June 2006. The strategy investigates the flood risks and potential costs and benefits of flood alleviation schemes in the Upper Calder catchment. The aims of the BNC Strategy were to: • Understand present and future flood risk;

• Identify effective and sustainable opportunities to manage flood risk;

• Understand interactions between flooding and the environment; and

• Include environmental enhancement via integrated flood risk management responses. Table 5.6 shows the number of properties from the National Property Database identified at risk of flooding in Pendle Borough from a 1% (1 in 100 year) flood event.

Table 5.6 Properties Identified at Risk of Flooding

Location Residential Properties Commercial Properties

Barrowford, Nelson 800 65

Lomeshaye and Carr Hall, Nelson 75 120

Middle of Trawden 35 11

Primet Bridge Area, Colne 4 55

Immediately downstream of Walverden Water 0 5

Walverden Water, between Walverden Park and 27 38 Bradley Road

The draft BNC Strategy divides the watercourses into Flood Management Units (FMUs), 25 of which are in Pendle Borough (3 on Trawden Beck, 13 on Pendle Water, 7 on Colne Water and 2 on Walverden Water). Appendix E details the FMU locations. Various flood management options were considered for each FMU with detailed technical and economic assessments of the most feasible over a 100 year timeframe. Table 5.7 summarises the findings for Pendle FMUs with properties at risk of flooding from a 1% flood event. Remaining FMUs not shown were only assessed for ‘Do Nothing’ and ‘Enhanced Maintenance’ flood management options.

Table 5.7 Assessment of Flood Management Options, BNC Strategy (Extract)

River and Reach (Critical Flood Risk Area) Walverden Trawden Colne Pendle Water Water FMU 1 2 5 5 6 7 9 10 1 2 Priority Score * * * 28.1 28.1 28.1 24 10 21.1 16.5 Option Description 1 Do Nothing 2 Do Minimum Enhanced z z z z 3 Maintenance z z z 4 Flood Proofing 5 Riverside Defences z z z z z z z z z z 6 Managed realignment z z z z z z z z z z 7 Off-line storage 8 On-line storage z z z z z z z z z z 9 By-pass channel z z z z z z z z 10 Channel conveyance z Eliminating pinch z z z z z z z z z z 11 points Enhanced flood z z z z z 12 warning 13 Development control Sustainable Urban z z z z z z z 14 Drainage Systems (SuDS) Land use z z z z z z z 15 management * Contains properties at risk of flooding from a 1% flood event, but flood management options not taken forward.

Likely to be feasible z Likely to be unfeasible Taken forward for economic appraisal

The priority scores for the selected flood management options are based on economic, social and environmental appraisal, with a maximum possible score of 44 (a combination of 20 for economics, 12 for people and 12 for environment). FMUs 5, 6 and 7 in Pendle Water score relatively high for the Pendle Flood Alleviation Scheme (see Box 5.3) which has now been implemented. Channel-specific measures (options 3 and 5 in Table 5.7) are identified as preferred options in the BNC Strategy, along with catchment-scale ‘best management practices’ (options 12 to 15) which will help manage current flood risk as well as prevent unnecessary increases in future flood risk. The BNC Strategy will be reviewed regularly to incorporate future changes in flood risk.

5.5.4 National Fluvial and Coastal Defence Database The Environment Agency’s National Fluvial and Coastal Defence Database (NFCDD) was interrogated for flood defence asset records in Pendle Borough. The database includes information on both formal flood defences as well as other structures that influence flood risk (including mill walls, culverts etc). In Pendle Borough, most of the assets fall into the latter category of informal flood defences (see Section 5.6.2). Limited records were available apart from along main rivers, although the Council is currently undertaking a programme on behalf of the Environment Agency to assess structures on the recently enmained COWs and populate the NFCDD with this information. Figure 5.9 shows the reaches where records were available. Flood defence asset records for Pendle indicated: • Stock Beck: Downstream of Barnoldswick records indicated the channel to have approximately a 1 in 70 year capacity; • Pendle, Colne and Walverden Waters: Channel and structure records indicated varying capacity in the region of 1 in 25 to 75 year. In addition to an assessment of capacity, condition grades are also recorded. Long stretches have asset grades of 1 to 2 (‘very good’ to ‘good’ condition), however there are significant sections with grades of 4 to 5 (‘poor’ to ‘bad’ condition). The records indicate assets in ‘poor’ condition are located in/ near: • Walverden Water, near the confluence with Hendon Brook COW;

• Colne Water, adjacent to Wanless Water and Swindon Clough COW;

• Pendle Water, left bank above Barrowford;

• Pendle Water, around Newbridge and Barrowford; and

• Pendle Water, downstream of the Hollin Mill COW.

5.6 Flood Alleviation

5.6.1 Flood Alleviation Schemes A number of schemes have been investigated to alleviate flooding in Pendle Borough. Unfortunately neither the Environment Agency nor Pendle Borough Council hold any reports documenting the flood alleviation schemes implemented in the Borough. Table 5.8 summarises implemented schemes in the Borough identified from a variety of other sources, predominantly newspapers, together with schemes planned for future implementation, largely based on the BNC Strategy. Note that this list does not include works to rectify sewer flooding problems undertaken by the water companies, and is not comprehensive, particularly with respect to non- Environment Agency schemes (including works undertaken by the Council or privately) as definitive records of these activities were not available. Figure 5.9 shows the location of the Pendle and Walverden Water flood alleviation schemes.

Table 5.8 Flood Alleviation Schemes

Scheme/ Area Year Details

Implemented

Pendle Flood Alleviation 2006 £5 million scheme to protect 500 homes and businesses in Barrowford and Scheme Lomeshaye which have flood 21 times in 130 years. Scheme included weir removal, strengthening of channel integrity, capacity improvements, culvert works. See Box 5.3. (Outcome of BNC Strategy for Pendle Water FMUs 5, 6 and 7.)

Walverden Water 2004- Some flood alleviation works carried out. 2005

Earby 2004 Some residents raised thresholds to prevent internal flooding of homes.

Westfield Mill, Gisburn 2004 Sections of culvert under former Westfield Mill site planned for upgrade as part of Road, Barnoldswick application for residential development.

Ghyll Meadows, 2002 £80k scheme for a new culvert and repair of damaged culverts to alleviate flood Barnoldswick risk.

M65, Pendle Water 2000 £55k scheme to reinstate undercut bank on M65, just north of J13. £0.9 million spent on a major scheme for banks along this whole reach of Pendle Water in 2002.

Barrowford Surface 1996 Scheme to pump excess surface water from Barrowford to discharge to Pendle Water Pumping Scheme Water downstream.

Planned 1

Walverden Water Flood 2007- Currently at design stage. Likely to include channel improvements, new flood Alleviation Scheme 2012 defences and flood storage. Construction planned 2007 to 2009 and ‘remedial works’ 2009 to 2012. (Outcome of BNC Strategy for Walverden Water FMUs 1 and 2.)

Pendle Water 2010 - BNC Strategy recommendations: 2028 ‘High priority structural remedial asset works’ between Reedyford FGS and Edge End Brook (Pendle Water FMUs 8 to 10) from 2010 to 2013.

‘Remedial works’ for Pendle Water FMUs 1 to 4 and 11 to 13 from 2020 to 2024.

Construction of a flood alleviation scheme for Pendle Water FMUs 9 and 10 between 2025 and 2028.

Trawden Beck 2020 - BNC Strategy recommendation for ‘remedial works’ between Skipton Road and 2038 Skipton Road Crossing (Trawden Beck FMUs 1 and 2).

Colne Water 2030 - BNC Strategy recommendation for ‘remedial works’ between Bridge Street and 2036 Philips Lane (Colne Water FMU 5). 1 All planned schemes are subject to funding constraints, and the dates provided in the BNC Strategy may change according to future priorities.

In addition to the above flood alleviation schemes, some reaches of watercourse in the Borough, Pendle and Colne Waters in particular, are lined by former mills, some now derelict. The riverside walls of these mills can act as flood defences, however in most cases the condition and integrity of the walls are not adequate for formal flood defence purposes. The historical ad- hoc construction of these flood defences in the Borough (many of which were reactive measures) means that there is a wide variety of Standards of Protection (SoPs) afforded by these informal flood defences. Since some of these mills are abandoned, it is expected many of the walls will be in poor condition.

Box 5.3 Pendle Flood Alleviation Scheme

The residents and businesses in Barrowford and Lomeshaye along Pendle Water have suffered the consequences of flooding on a number of occasions. In response to this, the Environment Agency implemented the Pendle Flood Alleviation Scheme, which was formally opened in June 2006. The scheme consists of multiple river works, including river training and re-sectioning, removal of a weir and bed regrading, the construction of flood walls, scour protection, bank stability improvements, and culvert improvements. The scheme also included new flood embankments, a new access bridge for Lomeshaye Industrial Estate and the demolition of several business units.

A design report for the Pendle Flood Alleviation Scheme was not available to the SFRA, however the Environment Agency have indicated that the design of the scheme pre-dates the current national Standard of Protection (SoP) which provides protection up to the 1% (1 in 100 year) flood event plus freeboard and climate change allowances. It is thought that the as-built scheme currently provides protection up to the 1% flood event without allowances. It is therefore not shown as a defence on the Environment Agency’s Flood Map as it does not meet the current SoP criteria. Any future increases in design flood level (e.g. due to climate change) will reduce the scheme’s current SoP.

Areas protected by the scheme remain in flood zones 2 and 3 (see Figure 5.9) as, although the flood risk has been significantly reduced, there remains a ‘residual risk’ of flooding (see Section 5.7).

Figure 5.9 shows the location of the Environment Agency main river banks that have been assessed in terms of SoP and condition as part of the NFCDD (see Section 5.5.4). Table 5.9 shows the average NFCDD asset condition from the BNC Strategy for Pendle Borough FMUs prioritised by the highest number of properties at risk of flooding from the 1% (1 in 100 year) flood event. The strategy recommends that these assets be surveyed in the near future to confirm their condition and SoP. This will allow improvements to be prioritised by both risk (which is dependent upon SoP and asset condition) and consequence (numbers of properties at risk).

Table 5.9 NFCDD Asset Condition in Pendle Borough

River FMU Average NFCDD Asset Prioritisation Rank Condition

Walverden Water 1 4 3 Pendle Water 5 3 4 Pendle Water 6 3 5 Pendle Water 7 2 7 Pendle Water 9 2 8 Trawden Beck 1 3 10 Note: This table is from the BNC Strategy. The missing prioritisation ranks are for FMUs outside of Pendle Borough. The NFCDD ranks the condition of assets between 1 (very good) and 5 (very poor).

Any future development planned alongside these watercourses will need to consider the risks associated with informal flood defences in further detail in the FRA, including consideration of the consequences of overtopping or failure.

5.7 Residual Flood Risk It is important to note that no flood alleviation scheme completely removes the risk of flooding. All schemes are designed to a specific design flood event and flooding will still take place if a more extreme event occurs. Furthermore, there is a risk that flood alleviation schemes could fail (either structurally or operationally). The term ‘residual risk’ is used to describe the risk that remains after taking flood alleviation measures into account. Risk is a product of probability and consequence; therefore although areas protected by flood alleviation schemes may be at a low risk of flooding, if these failed, the consequences would be very high (i.e. in terms of the damage to property and risk to life). This risk remains whatever the standard of flood defence, and PPS 25 will require an evaluation of this risk as part of the FRA for any development planned in a defended area. With respect to development planning and the guidance in PPS 25, areas in the high flood risk zone (i.e. zone 3) that are defended from flooding are not differentiated from those that are undefended, since there remains a residual risk if flood alleviation measures are overtopped or fail.

5.8 Climate Change

5.8.1 Implications for Flood Risk Over time, climate change could have a significant effect on flood risk, as it is expected to cause winters to become wetter and summers to become drier. The insurance industry has warned that premiums could rise as flood prone properties become more difficult to protect, and some properties may be unable to obtain insurance against flood altogether. Climate change effects could mean that extreme weather events such as droughts, floods and storms could become more common. The Ribble CFMP identifies climate change as potentially having the largest effect on flood risk in the CFMP area. For the North West, the UK Climate Impacts Programme (UKCIP) model predicts that by 2080, winter rainfall could increase by up to 30% and summer rainfall could decrease by up to 50%. Whilst overall summer rainfall is expected to decrease, there could be an increased likelihood of more intense summer storms. Urban heat island effects could potentially exacerbate this. Due to wetter winters, groundwater levels could increase in winter months, potentially causing groundwater flooding in prone areas. PPS 25 (Paragraph B9) recommends that an allowance be made for up to a 30% increase in peak river flows by 2110 to account for the potential effects of climate change based on current guidance. Increased storminess and higher peak rainfall values will also cause increases in runoff. Water companies have indicated that, under such scenarios, the current design standard for surface water drainage sewers (i.e. the 3.3% or 1 in 30 year design event) will need to take climate change into account. PPS 25 (Paragraph B10) recommends an allowance be made for up to a 15% increase in rainfall intensities by 2110 to account for the potential effects of climate change based on current guidance.

5.8.2 Implications for Development PPS 25 requires that flood risk and mitigation be assessed for the lifetime of any proposed development. The Sequential Test guides new development to areas of low flood risk, (i.e. zone 1). However, where development is proposed for the higher risk flood zones (i.e. zones 2 and 3), the potential effect of climate change on flood risk should be assessed in line with the guidance provided in PPS 25 (see Section 5.8.1) to ensure the robustness of any mitigation measures. The Environment Agency’s flood zones can provide some indication of areas where climate change might cause the most lateral expansion of inundation, by comparing zones 2 and 3 to see how rare, more extreme flows affect the floodplain extents. For development proposed in or near the boundaries of the higher risk flood zones, a detailed assessment of flood risk, including the potential effects of climate change, will be required in the FRA. In addition to fluvial flood risk, climate change must also be considered in the context of its potential to increase surface water runoff. An assessment of the potential effect of climate change on runoff and associated flood risk, and testing of mitigation measures for robustness, will be required in the FRA based on the guidance provided in PPS 25.

5.9 Land Use Land use and land use change may have a more immediate effect on the hydrology of a catchment, where step-changes in land use effect changes in the catchment’s responsiveness to rainfall events. The frequent location of development and urban areas in valley bottoms near major rivers often leaves them vulnerable to the effects of land use change in the upper catchment. The implications will depend on the extent of the land use change and the type of catchment (i.e. its geology, topography and the hydraulic connectivity of its watercourses, which largely affects how ‘flashy’ the catchment is in response to a rainfall event). A number of the catchments in Pendle Borough have characteristics that indicate they respond quickly to rainfall events (see Tables 5.2 to 5.4) which is supported by some records of historical ‘flash’ flooding. Broadly, there are three categories of land use change that could potentially impact on flood risk in Pendle Borough: 1. Moorland management (see ‘rural land use change’ in Section 5.5.2); 2. Change in agricultural land use; 3. Conversion from rural to urban land use. In the case of increasing urbanisation, SuDS systems have been developed as a way to manage drainage to mimic the natural (greenfield) runoff regime. The implementation of SuDS systems in new developments is instrumental in ensuring that the development does not adversely affect flood risk. This should be enforced at the development planning stage through PPS 25. Flood mitigation measures are discussed further in Section 7.3.

5.10 Geomorphology The steep topography (see Figure 5.8) and high rainfall of the upland areas of Pendle Borough means that many of the main watercourses are geomorphologically active, eroding material that is later deposited in downstream reaches. Although a natural process, the passage and accumulation of this sediment has the potential to reduce the capacity of channels downstream which can in turn increase flood risk. In problem areas where erosion exceeds natural levels as a result of human activity (see Section 5.9), remediation in source zones and/ or enhanced channel maintenance at accumulation zones downstream, may be necessary to mitigate the associated flood risks. The emerging Ribble CFMP identifies that fine sediment input upstream of Walverden Reservoir due to natural slope wastage accelerated by grazing is potentially reducing channel capacity. Overall, the CFMP indicates Colne and Pendle Waters are particularly sensitive to geomorphological effects. The BNC Strategy identified the need for an improved understanding of the geomorphology of watercourses in the area.

5.11 Assumptions and Uncertainty

5.11.1 Fluvial Flood Risk The assessment of fluvial flood risk in the Pendle SFRA has been primarily based on the Environment Agency’s flood zones. The limitations in the method for deriving these zones have been outlined in Box 5.1. A key aspect to note is that the flood zones derived using JFLOW do not account for structures in the floodplain, which includes informal flood defences and flood alleviation schemes. As a result, there will be areas in the Borough that are afforded some protection from these structures, but that remain in the high risk flood zones (i.e. zones 2 and 3). This is in line with the approach to development planning as set down in PPS 25, which recognizes there is residual risk associated with areas protected by flood alleviation schemes (see Section 5.7) and therefore directs development to areas of lower flood risk. However, there may be some cases where development is proposed in these areas to avoid urban blight, for example brownfield redevelopment. Detailed FRAs will be required to assess the flood risks more accurately, using more detailed site topography and flood models that include consideration of structures in the floodplain. Two flood models have been developed of watercourses in the Borough (see Table 5.5) which it may be possible to utilise subject to agreement with the model owner/ relevant authority. However where models have not currently been developed, it may be necessary to develop a new model to assess the fluvial flood risk to a proposed development more accurately.

5.11.2 Secondary Sources of Flood Risk Numerous records of flooding from drainage systems, overland flow and blocked culverts were collated for the study. This information mainly relates to flood events in recent history, primarily sourced from flood records kept by the Environment Agency and newspaper references. Some records of sewer flooding have also been obtained from United Utilities and Yorkshire Water. However, it is noted that it is not possible to quantify the risk of future flooding from these historical flood records as they represent particular hydrological events, and more extreme, or different, events could present different levels of risk in different locations.

Instead, they provide valuable background information to help identify and characterise the various flood risks present in Pendle Borough. This information can then be used to guide the focus of more detailed FRAs to minimise the flood risk associated with developments through appropriate planning, design and mitigation measures.