Helston Flood Risk Profile


Overview

Helston sits by the River Cober on the Lizard Peninsula just upstream of its outlet to Loe Pool.

Without the presence of Loe Bar, the River Cober at Helston would be tidal up to the boating lake at Coronation Park.

Helston has a historic leat system that runs through the town.

Rivers and catchments

The principal watercourse draining to Helston is the River Cober.

Other rivers and streams in the catchment include:

  • Tolcarne Stream
  • Medlyn Stream
  • Bodilly  Stream
  • Sithney Stream
  • Bosworgy Stream

and downstream of Helston but above Loe Pool

  • Penrose Stream
  • Carminowe Stream

Helston Leats

The Helston Leats are fed from an intake just downstream of the Bodilly Stream and River Cober confluence near Wendron. The supply channel to the leat is around 3km long.  The leat divides near the junction of the B3297 and Water Ma Trout on the north side of Gwealfolds.  The divided leats form 5km of channels discharging back into the River Cober through two outfalls at Lower Green.  The section of the leat from Wellmore Playground to the most upstream at Lower Green and known as Town Leat, this is designated as Main River.

Risk of flooding from rivers

More than 350 properties are at risk of fluvial (river) flooding in Helston. 
Around 280 of these are residential and 70 properties are commercial, including the sewage treatment works.

Risk of flooding from surface water

Around 480 properties are potentially at risk from surface water flooding. Of these around 400 are residential properties. 75 properties are commercial including: 2 schools and a hospital.

 You can view maps relating to the area via the following links:

Flood risk management in Helston

There are a number of existing linear flood defences in Helston and the surrounding area. The water level in Loe Pool is an important factor in managing Helston's flood risk.  A tunnel through Loe Bar is controlled by the Environment Agency to lower water levels in times of flood.

Helston is within the South Coastal Rivers Policy Unit of the West Cornwall Catchment Plan.  The policy for this unit is Option 5: “Areas of moderate to high flood risk where we can generally take further action to reduce flood risk”

The main urban area of Helston is categorised as a Critical Drainage Area.  Any development which occurs in a CDA requires a reduction in flood risk (betterment) rather than requiring a neutral impact.

Coastal Considerations

Whilst Helston is not currently at tidal flood risk Loe Pool and Loe Bar have a significant impavct on flood risk as the River Cober can become tidelocked and back up if the water level in Loe Pool becomes too high.

Loe Pool and Bar are covered by Policy Development Zone 7 and Management Area 17 of the  The Shoreline Management Plan. The long term policy of this area is managed realignment policy which would allow the barrier to respond to sea level rise and adjust its profile accordingly , helping to maintain the natural defence provided by the barrier.  The managed realignment policy would include continued maintenance of the drainage culverts.

Main challenges for local flood risk management in Helston

There are a number of key issues associated with flood risk management in the Helston area, these include;

  • The River Cober causes flooding to the St Johns area and recreation park and is impacted by water levels in Loe Pool
  • The flood defences on the River Cober are generally to a 1 in 50 year return period standard
  • The hydrology of Loe Pool and flood risk within Helston are inextricably linked
  • The leat system in Helston may be an integral feature of surface water drainage
  • The boating lake is under increasing risk of becoming tidally influenced through sea level rise
  • Parts of the Godolphin Road leat system are designated as a Grade II listed heritage asset

Helston is not on the coast but levels in the River Cober can be influenced by levels at Loe Pool which in turn can be affected by tide levels.  Further sea level rise may increase this influence and may also threaten the integrity of the bar at Loe.

There are a number of key issues associated with flood risk management in the Helston area, these include;

  • The River Cober causes flooding to the St Johns area and recreation park and is impacted by water levels in Loe Pool
  • The flood defences on the River Cober are generally to a 1 in 50 year return period standard
  • The hydrology of Loe Pool and flood risk within Helston are inextricably linked
  • The leat system in Helston may be an integral feature of surface water drainage
  • The boating lake is under increasing risk of becoming tidally influenced through sea level rise
  • Parts of the Godolphin Road leat system are designated as a Grade II listed heritage asset

Helston is not on the coast but levels in the River Cober can be influenced by levels at Loe Pool which in turn can be affected by tide levels.  Further sea level rise may increase this influence and may also threaten the integrity of Loe Bar..

Opportunities for flood risk management in Helston

  • Undertake a surface water management plan for Helston and include proposals for implementation
  • Review channel maintenance to ensure targeted maintenance is undertaken to reduce flood risk, particularly upstream of structures.
  • Investigate the potential of upstream storage areas on the River Cober
  • Investigate the feasibility of improvements to the flood alleviation scheme in Helston
  • Further investigate the links between land management practices, runoff and flood risk.

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