Benbecula (Potentially Vulnerable Area 02/06)

Local Plan District Local Authority Main Catchment 02 Comhairle nan Eilean Siar Coastal

Background

This Potentially Vulnerable Area (PVA) The main access route, the A865, runs comprises the entire island of down the centre of the PVA, with minor Benbecula. It has an area of roads and small populated areas spread approximately 76km² (Figure 1). mainly on the western side of the island. The which provides an important Topographically, the area is low-lying transport link is located close to the coast with numerous lochs throughout the on the northwest of the island. PVA. To the west the PVA is fringed by dunes. The total Annual Average Damages (AAD) for all flood sources is £469,000. Nearly 80% of the damages are attributed to coastal flooding, with river flooding contributing 20% of damages (Figure 2).

Figure 2: Annual Average Damages by Figure 1: Benbecula Potentially Flood Source Vulnerable Area

This area was designated as a PVA due to flood risk to properties, roads, Benbecula airport and to cultural heritage sites based on information available at the time of the National Flood Risk Assessment in 2009. Designation as a PVA means that further investigation of that flood risk was required. This has been carried out based on the flood hazard and risk maps published by SEPA in January 2014 together with input from the Local Plan District Partnership.

Summary of Impacts from all sources of flooding

Over 65% of the Annual Average Damages (AAD) result from flooding to residential properties, with a smaller proportion of damages coming from flooding to non- residential properties, agriculture, roads.

Most of the assets at risk of flooding lie to the west of the A865. This includes residential and non-residential properties at Creagorry and Lionacleit. The A865 itself is known to flood at Gramsdale as are the B892 at Pol na Cran and the B892 at where waves cause the carriageway to be blocked by debris.

A number of cultural heritage sites are identified as at risk, all of which are Scheduled Ancient Monuments and include prehistoric domestic and defensive sites. Cultural heritage sites do not contribute to the AAD total as it is difficult to quantify a monetary value for them.

Areas of environmentally designated sites are at risk of flooding. The sites affected include Aird and Borve, Benbecula Special Protection Area (SPA) and West Benbecula Lochs Site of Special Scientific Interest (SSSI).

Table 1 presents a summary of the receptors at risk from all sources of flooding in the different return periods (different probabilities of flooding in any one year). The contribution from the different receptors to the overall damages (by return period) is shown in Figure 3.

Figure 4 shows the location of receptors that are at medium to high risk of flooding from all sources in the PVA.

Table 1: Summary of Flood Risk from all sources High Risk Medium Risk Low Risk

1 in 10 year 1 in 200 year 1 in 1000 year Number of Residential 85 97 106 Properties at risk (out of 588) Number of Non-residential Properties at risk (out of 9 16 17 213) Number of People at risk 187 213 233 Community Facilities at risk 0 0 0 1 Electricity Generating 1 Electricity Generating Utilities at risk 3 Electricity Sub Stations Site Site 3 Electricity Sub Stations 4 Electricity Sub Stations Roads (64 locations) Roads (85 locations) Roads (88 locations) Transport Links at risk 0.02km 2 airport affected 0.05km 2 airport affected 0.05km 2 airport affected Environmental Designated 2 km 2 3 km 2 3 km 2 Areas (km 2) at risk Number of Cultural Heritage 5 7 7 Sites at risk Agricultural Land at risk 7 km 2 8 km 2 8 km 2 (km 2)

Figure 3: Damages by receptor and return period for flood risk from all sources Figure 4: Location of receptors at medium to high risk of flooding from all sources in the Benbecula PVA

Summary of existing local actions to manage flood risk

The B892 road (where it passes through Balivanich) is protected by rock revetments and the at Benbecula Airport is protected from erosion by concrete (Reno) mattresses and gabion walls on the foreshore. There is also a rock revetment further south of the town at Pol na Cran. A rock wall situated on the foreshore north of Uachdar provides protection to agricultural land from inundation by the sea. Shingle banks on the west coast of Nunton and northwest coast of Aird also protect agricultural land from inundation by the sea. Sand dunes provide natural protection to the airport, agricultural land and roads at Balivanich, Nunton, Griminish, Torlum and Lionacleit. Gualan Island situated to the west of the South Ford acts as a barrier island providing protection to the inner coastline from Atlantic storm waves but was breached during the January 2005 storm and remains in a severely eroded state.

The Benbecula Main Drain provides drainage to low-lying land in the west of Benbecula and has outfalls controlled by floodgates in Balivanich to the north and Lionacleit to the southwest. Another drainage canal, also controlled by a floodgate, flows from south and east of the airport to Uachdar in the north of the island. Maintenance of both of these drainage systems is important and responsibility for this is shared between Stòras Uibhist, Scottish Government Rural Inspectorates and Payments Division (SGRIPD), Scottish Water and local crofters.

The recently reconstructed causeway at North Ford maintains transport links between Benbecula and . The South Ford Causeway maintains transport links between Benbecula and .

Comhairle nan Eilean Siar takes flood risk into consideration as part of decisions related to land use planning, as outlined in Scottish Planning Policy. This includes ensuring that new developments are not permitted in areas at risk of flooding and that all new developments do not increase flood risk elsewhere.

Floodline, SEPA’s flood warning service, provides flood alerts for the Outer Hebrides.

Summary of Objectives to manage flood risk in PVA

Local Plan District

Initial Objective Indicator

Avoid an increasing the number of residential From an estimate of 224 residential and non-residential properties at risk from all properties sources of flooding. From an estimate of 152 non- residential properties

Benbecula (PVA 02/06)

Initial Objective Indicator

Reduce economic damages to residential and From an estimated total Annual non-residential properties at risk from coastal Average Damages for residential flooding. properties of £242,000 From an estimated total Annual Average Damages for non- residential properties of £44,000

Initial Objective Indicator

Reduce number of people at risk of river and From an estimate of 214 people coastal flooding.

Initial Objective Indicator

Reduce number of utilities at risk of coastal 2 electricity substations flooding

Initial Objective Indicator

Reduce disruption to transport at high risk 37 road locations from coastal flooding Airport

Initial objectives for cultural heritage and environmental designated sites may be added when information is available from the relevant body.

Summary of Measures to achieve Objectives

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