Flood investigation reports

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding of more than five commercial buildings in close proximity occurred during a single incident.

1.2 This investigation was undertaken following the flood incident at Brackmills, Northampton that occurred on Sunday 27th May 2018.

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of Catchment Area 

2.1 Brackmills Industrial Estate is located approximately 1.5 miles to the southeast of Northampton Town centre.

2.2 2 The western end of Caswell Road is at the base of a natural valley that runs from Hardingstone to the southwest for approximately 750 metres. Two watercourses combine and flow down to a catchment pond adjacent to the roundabout on Caswell Road.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 The rainfall fell on the catchment between approximately 19:00 and 20:00.

3.2 Surface Water Flow 

3.2.1 The main reported sources of flow to affect this area were from the direction of Houghton Hill and Brackmills Country Park.

3.2.2 To the west of Caswell Road, the surface runoff from Houghton Hill flowed along the watercourse overtopping and washing away the stone weirs within. This in turn led to an increased flow into the attenuation pond.

3.2.3 It was reported that the pond filled and overtopped onto and across the roundabout. In turn this overtopped the opposite kerb and flowed down the verge into the adjacent commercial site.

3.2.4 The flood water from the overtopped pond also travelled along Caswell Road and into the adjacent commercial site flooding both sides and through the ground floor.

3.2.5 Properties in Sketty Close reported that the surface water came from the rear of their properties and was heavily mudded in appearance.

3.2.6 The surface water at a commercial site on Gowerton Road flowed into the rear of the property, down both sides, and out to Gowerton Road. The facing brickwork to the retaining wall to the rear of this property was washed away by the force of the flow.

3.3 Standing Water 

3.3.1 The majority of surface water from the surrounding catchment flowed to low points on Caswell Road, Burryport Road and Gowerton Road.

3.3.2 Surface water that flowed to the rear of the properties first increased in depth against the rear walls before flowing through and against the properties.

3.3.3 Caswell Road, Burryport Road and Gowerton Road were all reported as being flooded above the road kerb levels.

4.0 Cause of Flooding  

4.1 In any flood incident there can be multiple factors which result in the flooding witnessed. From the information received, the key factors are:

• The flooding in the Brackmills area was caused by intense heavy rainfall beyond the design capacity of drainage systems across the catchment. 
• The capacity of the attenuation pond adjacent to the Caswell Road roundabout was quickly exceeded by the volume of incoming flow, this may have been hastened by the performance of the vortex flow control if it were not to have been functioning properly at the time of the flooding. 
• The overtopping of the watercourse to the rear of a commercial property on Caswell Road was caused by the excessive surface water flow from the broader catchment area. The partial blockage from the tree trunk within the watercourse partially diverted the flow into the rear of the adjacent property. 
• It is understood that the retaining wall to the rear of a commercial property failed during the storm. 
• The Brackmills area is situated within a predominantly urban surface water catchment area with a large greenfield catchment to the west and south. Underlying topography channels the surrounding greenfield surface water in an easterly and northerly direction to the low points through the commercial properties. 
• There was no prior warning of the location and extent of heavy rainfall, or that the rainfall would be so intense and localised in the affected areas. 
• There are no community or property level resilience measures in place that could have been deployed. 

5.0 Recommendations 

5.1 The following are the Key Recommendations resulting from the flood incident:

• For Risk Management Authorities and riparian owners to investigate their systems and assets. 
• For Risk Management Authorities and riparian owners to undertake maintenance to keep their systems operating efficiently. 
• Owners of affected properties should consider preparing or reviewing and updating their Business Continuity Plans and implementing Property Level Resilience. 
• With support from Flood Risk Management Authorities, the community should make efforts to: 
  • Appoint Community Flood Wardens, 
  • Review the existing Brackmills Emergency Plan, 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• The Lead Local Flood Authority should coordinate with other Flood Risk Management Authorities to extend publicity of the existing information available. 
• The Lead Local Flood Authority should work with the community and Local Authorities to assess the viability of options for engineering schemes to reduce flood risk. This might include community level flood resilience measures, improving drainage to accommodate extreme rainfall events, providing attenuation storage areas and creating formal overland flood flow routes.

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding of at least one residential property has been experienced more than once in the last five years.

1.2 This investigation was undertaken following the flood incident at Breezehill, Northampton that occurred on Sunday 27th May 2018.

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of Catchment Area 

2.1 The affected area of Breezehill is located in a surface water catchment area that extends approximately 500 metres to the north.  

2.2 The catchment is urban in nature with approximately 90% developed. Areas of open space comprise gardens and road verges.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 The rainfall fell on the catchment between approximately 19:00 and 21:00.

3.2 Surface Water Flow 

3.2.1 Water flowed down the catchment from north to south through residential areas. At the south end of Breezehill, water flowed from northeast to southwest, from the carriageway of Breezehill through residential property.

3.3 Standing Water 

3.3.1 The affected properties are situated in a localised low point where water increased in depth around buildings before it could continue to flow away to the southwest.

3.3.2 The carriageway of the turning head at the south end of Breezehill filled with water until it reached the height of the back of the footway. At this point it spilled over to private areas.

4.0 Cause of Flooding  

4.1 In any flood incident there can be multiple factors which result in the flooding witnessed. From the information received, the key factors are:

• The flooding in the Breezehill area was caused by intense heavy rainfall beyond the design capacity of drainage systems across the catchment. This led to excess surface water flowing over ground, following localised topography to low points. 
• The affected area is situated at the bottom of a relatively large, predominantly urban surface water catchment area. Affected dwellings are situated in a localised bowl with no means for surface water to runoff to other areas. 
• There was no prior warning of the location and extent of heavy rainfall, or that the rainfall would be so intense and localised in the area affected.  
• Limited property level resilience measures were in place on the properties, but these were ineffective in preventing flood water ingress. 
• Works to increase the capacity of the public surface water sewer system were in the process of being commissioned at the time of the flooding. These works are to bring the sewers to current design standards and the risk of flooding remains in extreme rainfall events and where surface water cannot drain into the sewer system fast enough. 

5.0 Recommendations 

5.1 The following are the Key Recommendations resulting from the flood incident:

• Owners of affected properties should consider preparing a Household Emergency Plan and implementing Property Level Resilience. 
• With support from Flood Risk Management Authorities, the community should make efforts to: 
  • Appoint Community Flood Wardens, 
  • Prepare a Community Emergency Plan, 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• The Lead Local Flood Authority should coordinate with other Flood Risk Management Authorities to extend publicity of the existing information available. 
• The LLFA should work with the community and Risk Management Authorities to assess the viability of options for engineering schemes to reduce flood risk. This might include community level flood resilience measures, improving drainage to accommodate extreme rainfall events, providing attenuation storage areas and creating formal overland flood flow routes. 
• Local Authorities, Emergency Services and other relevant response groups should continue to work together, and review their immediate and follow up response to the emergency.  

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding of more than five residential or commercial buildings in close proximity occurred during a single incident.

1.2 This investigation was undertaken following the flood incident at Briar Hill, Northampton that occurred on Sunday 27th May 2018.

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of Catchment Area 

2.1 The affected area of Briar Hill is largely within the residential area between Ring Way, Thorn Hill and Ashbrow Road. These streets are located in a surface water catchment area that extends approximately 950 metres to the south.

2.2 The catchment is urban in nature with approximately 90% developed. The remaining open space includes relatively large areas of grassed open space set out as wide pedestrian avenues.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 The rainfall fell on the catchment between approximately 19:00 and 21:00.

3.2 Surface Water Flow 

3.2.1 Surface water flowed from south to north over the catchment, with the cumulative flow increasing in depth and velocity as it flowed north and rainfall worsened.

3.2.2 The main flows of surface water were from south to north in the carriageways of Thorn Hill and Ring Way.

3.2.3 Flows of surface water were formed by smaller catchments localised around specific areas.

3.3 Standing Water 

3.3.1 The majority of surface water from the surrounding catchment flowed to a low point on Ring Way and became deep enough to cover car wheels.

3.3.2 The affected property at Plantagenet Square is constructed in a localised low point where standing water increased in depth.

3.3.3 Surface water increased in depth at the front or rear of rows of dwellings positioned in a level straight line perpendicular to the natural fall of the local topography.

4.0 Cause of Flooding  

4.1 The flooding in the Briar Hill area was caused by intense heavy rainfall beyond the design capacity of drainage systems across the catchment.

4.2 The affected areas are situated within a relatively large, predominantly urban surface water catchment area. Ring Way, an area of Plantagenet Square and some localised dwellings are situated in localised bowls with no means for surface water to runoff to other areas.

4.3 There was no prior warning of the location and extent of heavy rainfall, or that the rainfall would be so intense and localised in the affected areas.

4.4 There are no community or property level resilience measures in place that could have been deployed.

5.0 Recommendations 

5.1 The following are the Key Recommendations resulting from the flood incident:

• Owners of affected properties should consider preparing a Household Emergency Plan and implementing Property Level Resilience. 
• With support from Flood Risk Management Authorities, the community should make efforts to: 
  • Appoint Community Flood Wardens, 
  • Prepare a Community Emergency Plan, 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• The Lead Local Flood Authority should coordinate with other Flood Risk Management Authorities to extend publicity of the existing information available. 
• The LLFA should work with the community and Risk Management Authorities to assess the viability of options for engineering schemes to reduce flood risk. This might include community level flood resilience measures, improving drainage to accommodate extreme rainfall events, providing attenuation storage areas and creating formal overland flood flow routes. 
• Local Authorities, Emergency Services and other relevant response groups should continue to work together, and review their immediate and follow up response to the emergency. 

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding of more than five residential or commercial buildings in close proximity occurred during a single incident.

1.2 This investigation was undertaken following the flood incident in Crofters Close to Augusta Avenue, and Turnberry Lane areas of Northampton that occurred on Sunday 27th May 2018.

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of Catchment Area 

2.1 The affected area of Crofters Close through to the west end of Augusta Avenue is located in a surface water catchment area that extends approximately 400m from north to south.

2.2 The affected area to the east end of Augusta Avenue is located in a surface water catchment area that extends approximately 400m from north to south, via a natural valley.

2.3 The affected area of Turnberry Lane is located in a surface water catchment area that extends across the golf course for approximately 500m from south to north.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 The rainfall fell on the catchment between approximately 19:00 and 21:00.

3.2 Surface Water Flow 

3.2.1 The main flows of surface water were:

• North to south within the cul-de-sac off Crofters Close to property at lowest point. 
• From Rowtree Road onto Downsway heading south through front and rear gardens. 
• To the west of Augusta Avenue the flow was reported to come from the north onto Augusta Avenue and flooding south into front and rear garden of a residential property. 
• To the east of Augusta Avenue the flow was north to south via the watercourse then backing up behind the culvert and flooding around to the rear of one property then onto Augusta Avenue and down the driveway of a second property. 
• To Turnberry Lane the surface water flowed from south to north from the golf course to the rear of properties on Turnberry Lane. 

3.3 Standing Water 

3.3.1 The majority of surface water from the surrounding catchment flowed to low points.

3.3.2 Surface water that flowed to the rear of the properties first increased in depth against the rear walls and fencing of the gardens before flowing through and against the dwellings.

3.3.3 Standing water was reported over the drainage gullies along the edge of the golf course to the rear of Turnberry Lane.

4.0 Cause of Flooding  

4.1 In any flood incident there can be multiple factors which result in the flooding witnessed. From the information received, the key factors are:

• The flooding in the Crofters Close to Augusta Avenue, and Turnberry Lane area was caused by intense heavy rainfall beyond the design capacity of drainage systems across the catchment.  
• Long grass cuttings were also reported with the grass having been extremely overgrown and having been cut a couple of days before. These cuttings were washed to the gully locations and potentially affected the efficiency of the gully.  
• The capacity of the culvert from the watercourse in Augusta Avenue was exceeded by the flow received down the watercourse.  
• The partial overgrowth and silting to the culvert outfall and adjacent obstruction within the open watercourse between Turnberry Lane and Belfry Lane restricted the intended flow from upstream.  
• There was no prior warning of the location and extent of heavy rainfall, or that the rainfall would be so intense and localised in the affected areas. 
• There are no community or property level resilience measures in place that could have been deployed. 

5.0 Recommendations 

5.1 The following are the Key Recommendations resulting from the flood incident:

• Owners of affected properties should consider preparing a Household Emergency Plan and implementing Property Level Resilience. 
• Riparian owners should ensure watercourses are clear and maintained to ensure satisfactory flow of water. 
• With support from Flood Risk Management Authorities, the community should make efforts to: 
  • Appoint Community Flood Wardens, 
  • Prepare a Community Emergency Plan, 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• The Lead Local Flood Authority should coordinate with other Flood Risk Management Authorities to extend publicity of the existing information available. 
• The LLFA should work with the community and Risk Management Authorities to assess the viability of options for engineering schemes to reduce flood risk. This might include community level flood resilience measures, improving drainage to accommodate extreme rainfall events, providing attenuation storage areas and creating formal overland flood flow routes.

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding of more than five residential or commercial buildings in close proximity occurred during a single incident.

1.2 This investigation was undertaken following the flood incident at East Hunsbury, Northampton that occurred on Sunday 27th May 2018.

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of Catchment Area 

2.1 The affected area of East Hunsbury is located in a surface water catchment area that is bounded by Grangewood Park to the west and Penvale Park to the east.  

2.2 Grangewood Park is a natural valley that runs north to south, between the Tesco Supermarket site on Clannell Road and Rowtree Road.

2.3 Penvale Park is another natural valley that runs east to west, between the site of Wootton Police Headquarters and Hilldrop Road.

2.4 The catchment is predominantly urban with approximately 80% developed with the remaining as open space.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 The rainfall fell on the catchment between approximately 19:00 and 21:00.

3.2 Surface Water Flow 

3.2.1 The main reported sources of flow to affect this area were from Grangewood Park and Hilldrop/Penvale Park.

3.2.2 Surface water flow was described as fast flowing and deepening around low points adjacent to the properties.

3.3 Standing Water 

3.3.1 The majority of surface water from the surrounding catchment flowed to low points on Rowtree Road, Hilldrop Road and Penvale Park, to the rear of Lichfield Drive.

3.3.2 Surface water that flowed to the rear of the properties first increased in depth against the rear walls and fencing of the gardens before flowing through and against the dwellings.

4.0 Cause of Flooding  

4.1 In any flood incident there can be multiple factors which result in the flooding witnessed. From the information received, the key factors are:

• The flooding in the East Hunsbury area was caused by intense heavy rainfall beyond the design capacity of drainage systems across the catchment. 
• The blockage to the culvert from the watercourse in Grangewood Park prevented the intended flow beneath Rowtree Road. 
• Long grass cuttings were also reported with the grass having been extremely overgrown and having been cut a couple of days before. These cutting were washed to the gully locations and potentially affected the efficiency of the gully. 
• The East Hunsbury area is situated within a relatively large, predominantly urban surface water catchment area. Underlying topography channels the surface water in a southerly and easterly direction to the low points through the private gardens. 
• There was no prior warning of the location and extent of heavy rainfall, or that the rainfall would be so intense and localised in the affected areas. 
• There are no community or property level resilience measures in place that could have been deployed. 

5.0 Recommendations 

5.1 The following are the Key Recommendations resulting from the flood incident:

• Owners of affected properties should consider preparing a Household Emergency Plan and implementing Property Level Resilience. 
• With support from Flood Risk Management Authorities, the community should make efforts to: 
  • Appoint Community Flood Wardens, 
  • Prepare a Community Emergency Plan, 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• The Lead Local Flood Authority should coordinate with other Flood Risk Management Authorities to extend publicity of the existing information available. 
• The LLFA should work with the community and Risk Management Authorities to assess the viability of options for engineering schemes to reduce flood risk. This might include community level flood resilience measures, improving drainage to accommodate extreme rainfall events, providing attenuation storage areas and creating formal overland flood flow routes. 

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding of more than five residential buildings in close proximity occurred during a single incident.

1.2 This investigation was undertaken following the flood incident at Gloucester Crescent, Northampton that occurred on Sunday 27th May 2018.

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of Catchment Area 

2.1 Brackmills Industrial Estate is located approximately 1.5 miles to the southeast of Northampton Town centre.

2.2 2 The western end of Caswell Road is at the base of a natural valley that runs from Hardingstone to the southwest for approximately 750 metres. Two watercourses combine and flow down to a catchment pond adjacent to the roundabout on Caswell Road.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 The rainfall fell on the catchment between approximately 19:00 and 20:00.

3.2 Surface Water Flow 

3.2.1 The main flows of surface water were as flows:  

• South to north from cemetery to rear of properties on Coverack Close.  
• South to north on Redruth Close, and footway to rear of gardens on Friars Avenue. 
• East and west on Gloucester Crescent to lowest point, then north to open space south of Blenheim Road. 
• South to north on east side of Gloucester Crescent, then northeast on footway connecting Gloucester Crescent to Pleydell Road, and north to rear gardens of Blenheim Road.  
• West to east from Briar Hill Walk to Towcester Road. 

3.3 Standing Water 

3.3.1 Areas of standing water at low points in Gloucester Crescent were short lived. Flood water tended to flow relatively quickly from south to north.

3.3.2 Houses, fences and walls were obstacles that restricted the flow of flood water and caused localised deepening.

3.3.3 Surface water increased in depth at the front or rear of rows of dwellings positioned in a level straight line perpendicular to the natural fall of the local topography.

4.0 Cause of Flooding  

4.1 In any flood incident there can be multiple factors which result in the flooding witnessed. From the information received, the key factors are:

• The flooding in the Gloucester Crescent area was caused by intense heavy rainfall beyond the design capacity of drainage systems across the catchment. 
• The affected areas around Gloucester Crescent and Towcester Road are situated at the base of natural valleys within a predominantly urban surface water catchment area. 
• There was no prior warning of the location and extent of heavy rainfall, or that the rainfall would be so intense and localised in the affected areas. 
• There are no community or property level resilience measures in place that could have been deployed. 

5.0 Recommendations 

5.1 The following are the Key Recommendations resulting from the flood incident:

• Owners of affected properties should consider preparing a Household Emergency Plan and implementing Property Level Resilience. 
• With support from Flood Risk Management Authorities, the community should make efforts to: 
  • Appoint Community Flood Wardens, 
  • Prepare a Community Emergency Plan, 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• The Lead Local Flood Authority should coordinate with other Flood Risk Management Authorities to extend publicity of the existing information available. 
• The LLFA should work with the community and Risk Management Authorities to assess the viability of options for engineering schemes to reduce flood risk. This might include community level flood resilience measures, improving drainage to accommodate extreme rainfall events, providing attenuation storage areas and creating formal overland flood flow routes. 
• Local Authorities, Emergency Services and other relevant response groups should continue to work together, and review their immediate and follow up response to the emergency. 

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding of more than five residential or commercial buildings in close proximity occurred during a single incident.

1.2 This investigation was undertaken following the flood incident at Hardingstone, Northampton that occurred on Sunday 27th May 2018.

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of Catchment Area 

2.1 The affected area of Hardingstone is located at the head of a surface water catchment area that extends approximately 500m to the north and north east.  

2.2 The catchment is urban in nature with approximately 90% developed. Areas of open space comprise gardens and road verges.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 The rainfall fell on the catchment between approximately 19:00 and 21:00.

3.2 Surface Water Flow 

3.2.1 Water flowed across the catchment from south to north and west to east through residential areas. Water flooded and flowed along High Street and Coneygree.

3.3 Standing Water 

3.3.1 The majority of surface water from the surrounding catchment flowed to low points on High Street, Bouverie Road and Coneygree.

3.3.2 Surface water that flowed around the properties and increased in depth against the rear walls and fencing of the gardens before flowing through and against the dwellings.

3.3.3 Standing water was reported to be 1 to 2 feet deep in Coneygree.

3.3.4 Standing water drained down over a couple of days following the rainfall, with most flood water around the properties subsiding by the next day. The standing water receded from the road the following day and from the gardens over 2-3 days.

4.0 Cause of Flooding  

4.1 In any flood incident there can be multiple factors which result in the flooding witnessed. From the information received, the key factors are:

• The flooding in the Hardingstone area was caused by intense heavy rainfall beyond the design capacity of drainage systems across the catchment. This led to excess surface water flowing over ground, following localised topography to low points. 
• The Hardingstone area is situated within a relatively large, predominantly urban surface water catchment area. Underlying topography channels the surface water in a northerly and easterly direction to the low points through the private gardens. 
• There was no prior warning of the location and extent of heavy rainfall, or that the rainfall would be so intense and localised in the affected areas. 
• There are no community or property level resilience measures in place that could have been deployed. 

5.0 Recommendations 

The following are the Key Recommendations resulting from the flood incident:

• Owners of affected properties should consider preparing a Household Emergency Plan and implementing Property Level Resilience. 
• With support from Flood Risk Management Authorities, the community should make efforts to: 
  • Appoint Community Flood Wardens, 
  • Prepare a Community Emergency Plan, 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• The Lead Local Flood Authority should coordinate with other Flood Risk Management Authorities to extend publicity of the existing information available. 
• The Lead Local Flood Authority should work with the community and Local Authorities to assess the viability of options for engineering schemes to reduce flood risk. This might include community level flood resilience measures, improving drainage to accommodate extreme rainfall events, providing attenuation storage areas and creating formal overland flood flow routes. 

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding of more than five residential or commercial buildings in close proximity occurred during a single incident.

1.2 This investigation was undertaken following the flood incident at Knaphill Crescent, Northampton that occurred on Sunday 27th May 2018.

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of Catchment Area 

2.1 The Knaphill Crescent area of Briar Hill includes Hunsbarrow Road, Rainsborough Crescent and Axe Head Road. These streets are located in a surface water catchment area that extends approximately 750 metres to the south.

2.2 The catchment is urban in nature with approximately 90% developed. The remaining open space includes pedestrian avenues of ‘The Causeway’ and ‘Hunsbury Walk’, radiating from the games court and public open space in the centre of this residential area.

2.3 To the north, Hunsbarrow Road, a disused railway and the Grand Union Canal are effectively barriers that form a disconnect between the catchment area and the watercourses which this would have naturally drained to.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 The rainfall fell on the catchment between approximately 19:00 and 20:00.

3.2 Surface Water Flow 

3.2.1 The deepest areas of flooding with the greatest volume of water were in the areas of Knaphill Crescent and Rainsborough Crescent.

3.2.2 The main flows of surface water were from south to north on Hunsbarrow Road, and from The Causeway open space to Hembury Place and Axe Head Road. Water flowed from Hunsbarrow Road into Knaphill Crescent.

3.3 Standing Water

3.3.1 The majority of surface water from the surrounding catchment flowed to a low point on Hunsbarrow Road and Knaphill Crescent and became deep enough to almost cover cars.

3.3.2 Surface water flowed to the rear of properties on Rainsborough Cresent, Axe Head Road and Knaphill Crescent and increased in depth against the rear of the dwellings.

3.3.3 Surface water increased in depth at the front or rear of rows of dwellings positioned in a level straight line perpendicular to the natural fall of the local topography.

4.0 Cause of Flooding  

4.1 In any flood incident there can be multiple factors which result in the flooding witnessed. From the information received, the key factors are:

• The flooding in the Knaphill Crescent area was caused by intense heavy rainfall beyond the design capacity of drainage systems across the catchment. 
• The affected area is situated at the bottom of a relatively large, predominantly urban surface water catchment area. Knaphill Crescent, Rainsborough Crescent and some localised dwellings are situated in localised bowls with no means for surface water to runoff to other areas. 
• There was no prior warning of the location and extent of heavy rainfall, or that the rainfall would be so intense and localised in the area affected. 
• There are no community or property level resilience measures in place that could have been deployed. 

5.0 Recommendations 

5.1 The following are the Key Recommendations resulting from the flood incident:

• Owners of affected properties should consider preparing a Household Emergency Plan and implementing Property Level Resilience. 
• With support from Flood Risk Management Authorities, the community should make efforts to: 
  • Appoint Community Flood Wardens, 
  • Prepare a Community Emergency Plan, 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• The Lead Local Flood Authority should coordinate with other Flood Risk Management Authorities to extend publicity of the existing information available. 
• The LLFA should work with the community and Risk Management Authorities to assess the viability of options for engineering schemes to reduce flood risk. This might include community level flood resilience measures, improving drainage to accommodate extreme rainfall events, providing attenuation storage areas and creating formal overland flood flow routes. 
• Local Authorities, Emergency Services and other relevant response groups should continue to work together, and review their immediate and follow up response to the emergency. 

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding of more than five residential or commercial buildings in close proximity occurred during a single incident.

1.2 This investigation was undertaken following the flood incident at St Leonard’s Road, Northampton that occurred on Sunday 27th May 2018.

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of Catchment Area 

2.1 St Leonard’s Road is located in a surface water catchment area that extends approximately 1.5km to the south. In effect, this is a natural valley between the A508 London Road and A5123 Towcester Road with St Leonard’s Road at the base.

2.2 The catchment is urban in nature with approximately 75% developed. The remaining open space includes recreation grounds, a cemetery and school fields.

2.3 The railway and industrial areas north of St Leonard’s Road introduces a disconnect between the catchment area and the watercourses which this would have naturally drained to.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 The rainfall fell on the catchment between approximately 19:00 and 21:00.

3.2 Surface Water Flow 

3.2.1 Surface water flowed south to north on London Road, Haines Road and Towcester Road. Surface water also flowed through alleyways at the rear of properties on the south side of St Leonard’s Road, causing water to approach dwellings from the rear.

3.2.2 Surface water also flowed to the service road north of St Leonard’s Road affecting garages.

3.3 Standing Water 

3.3.1 Surface water from the surrounding catchment flowed to a low point on St Leonard’s Road approximately 120 metres west of London Road. This gradually increased in depth to approximately 300 – 600mm.

3.3.2 Surface water that flowed to the rear of properties on the south side of St Leonard’s Road increased in depth against the rear of the dwellings. This increased in depth to 900mm in some places.

4.0 Cause of Flooding  

4.1 The flooding in the St Leonard’s Road area was caused by intense heavy rainfall beyond the design capacity of drainage systems across the catchment.

4.2 St Leonard’s Road is situated at the bottom of a relatively large, predominantly urban surface water catchment area. It is situated in a bowl with no means for surface water to runoff to other areas.

4.3 There was no prior warning to identify the location and extent of such intense heavy rainfall.

4.4 There are no community or property level resilience measures in place that could have been deployed.

5.0 Recommendations 

5.1 The following are the Key Recommendations resulting from the flood incident:

• Owners of affected properties should consider preparing a Household Emergency Plan and implementing Property Level Resilience. 
• With support from Flood Risk Management Authorities, the community should make efforts to: 
  • Appoint Community Flood Wardens, 
  • Prepare a Community Emergency Plan, 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• The Lead Local Flood Authority should coordinate with other Flood Risk Management Authorities to extend publicity of the existing information available. 
• The LLFA should work with the community and Risk Management Authorities to assess the viability of options for engineering schemes to reduce flood risk. This might include community level flood resilience measures, improving drainage to accommodate extreme rainfall events, providing attenuation storage areas and creating formal overland flood flow routes. 
• Local Authorities, Emergency Services and other relevant response groups should continue to work together, and review their immediate and follow up response to the emergency. 

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding of more than five residential or commercial buildings in close proximity occurred during a single incident.

1.2 This investigation was undertaken following the flood incident at Stevenson Street, Northampton that occurred on Sunday 27th May 2018.

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of Catchment Area 

2.1 The Stevenson Street area of Far Cotton includes Stevenson Street, Pilgrims Place, Queen Eleanor Road and Forest Road. These streets are located in a surface water catchment area that extends approximately 800 metres to the south.

2.2 The catchment is urban in nature with approximately 80% developed. The remaining open space includes allotments and school playing fields.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 The rainfall fell on the catchment between approximately 19:00 and 21:00.

3.2 Surface Water Flow 

3.2.1 The main flows of surface water were:

• From southwest corner of Pilgrims Place to the north, to front and rear of properties on the west side of the road. 
• Across the lowest point of Queen Eleanor Road, from south to north. 
• North to south through front and rear gardens of the properties on one side of Stevenson Street.  
• Across the lowest point of Forest Road, from south to north, finding a flow path between two blocks of terraced housing at this low point to continue north. 

3.3 Standing Water 

3.3.1 Flood water tended to flow relatively quickly from south to north. Areas of standing water at low points in Queen Eleanor Road and Forest Road were short lived.

3.3.2 Walls and fences in gardens restricted the flow of surface water and caused temporary, localised deepening of flood water.

4.0 Cause of Flooding  

4.1 In any flood incident there can be multiple factors which result in the flooding witnessed. From the information received, the key factors are:

• The flooding in the Stevenson Street area was caused by intense heavy rainfall beyond the design capacity of drainage systems across the catchment. 
• The affected area is situated at the base of a natural valley within a predominantly urban surface water catchment area. 
• There was no prior warning of the location and extent of heavy rainfall, or that the rainfall would be so intense and localised in the affected areas. 
• There are no community or property level resilience measures in place that could have been deployed. 

5.0 Recommendations 

5.1 The following are the Key Recommendations resulting from the flood incident:

• Owners of affected properties should consider preparing a Household Emergency Plan and implementing Property Level Resilience. 
• With support from Flood Risk Management Authorities, the community should make efforts to: 
  • Appoint Community Flood Wardens, 
  • Prepare a Community Emergency Plan, 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• The Lead Local Flood Authority should coordinate with other Flood Risk Management Authorities to extend publicity of the existing information available. 
• The LLFA should work with the community and Risk Management Authorities to assess the viability of options for engineering schemes to reduce flood risk. This might include community level flood resilience measures, improving drainage to accommodate extreme rainfall events, providing attenuation storage areas and creating formal overland flood flow routes. 
• Local Authorities, Emergency Services and other relevant response groups should continue to work together, and review their immediate and follow up response to the emergency. 

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding of more than five residential or commercial buildings in close proximity occurred during a single incident.

1.2 This investigation was undertaken following the flood incident at Thames Road and Avebury Way, Northampton that occurred on Sunday 27th May 2018.  

1.2 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of Catchment Area 

2.1 The affected area of Thames Road is located in a surface water catchment area that extends approximately 1km to the east to beyond the A45 to include Stourhead Drive and the linear area of park land to the southeast, between the rear of Stourhead Drive and Rea Close.

2.2 The affected area of Avebury Way is located in a surface water catchment area that extends approximately 400m to the north to beyond the A5076.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 The rainfall fell on the catchment between approximately 19:00 and 21:00.

3.2 Surface Water Flow 

3.2.1 The main reported sources of flow to affect the Thames Road area were from the rear of the properties however only 2 properties have reported any internal flooding.

3.2.2 On Avebury Way the surface water flowed down the road to the low point around a couple of properties.

3.2.3 Surface water flow was described as fast flowing and deepening around low points adjacent to the properties.

3.3 Standing Water 

3.3.1 The majority of surface water from the surrounding catchment flowed to low points on Thames Road and Avebury Way.

3.3.2 The manhole covers in Thames Road were reported to be initially lifting under the pressure of the flow and a resident later lifted one of the covers completely to enable the flooding to the road to escape more easily.

3.3.3 Standing water was reported to be up to 450mm deep to one garden and 200-250mm across the road.

4.0 Cause of Flooding  

4.1 In any flood incident there can be multiple factors which result in the flooding witnessed. From the information received, the key factors are:

• The flooding in the Thames Road and Avebury Way was caused by intense heavy rainfall beyond the design capacity of drainage systems across the catchment. 
• The Thames Road area is situated within a predominantly urban surface water catchment area. Underlying topography channels the surface water in an easterly direction to the low points through the private gardens. 
• There was no prior warning of the location and extent of heavy rainfall, or that the rainfall would be so intense and localised in the affected areas.  
• There are no community or property level resilience measures in place that could have been deployed. 

5.0 Recommendations 

5.1 The following are the Key Recommendations resulting from the flood incident:

• Owners of affected properties should consider preparing a Household Emergency Plan and implementing Property Level Resilience. 
• With support from Flood Risk Management Authorities, the community should make efforts to: 
  • Appoint Community Flood Wardens, 
  • Prepare a Community Emergency Plan, 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• The Lead Local Flood Authority should coordinate with other Flood Risk Management Authorities to extend publicity of the existing information available. 
• The LLFA should work with the community and Risk Management Authorities to assess the viability of options for engineering schemes to reduce flood risk. This might include community level flood resilience measures, improving drainage to accommodate extreme rainfall events, providing attenuation storage areas and creating formal overland flood flow routes. 

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of Northamptonshire Council (NNC). Internal flooding of more than five residential in close proximity occurred during a single incident, meeting the threshold.  

1.2 This investigation was undertaken following the flood incident at Woodgate Road, Northampton that occurred on Sunday 27th May 2018.

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of catchment area 

2.1 The affected area of Woodgate Road is located in a surface water catchment area that extends approximately 500 metres to the north.

2.2 The catchment is urban in nature with approximately 90% developed. Areas of open space comprise gardens and road verges.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 The rainfall fell on the catchment between approximately 19:00 and 21:00.

3.2 Surface Water Flow 

3.2.1 The main reported sources of flow to affect this area were from the school and nursery grounds immediately to the north of the affected area. Water flowed down the catchment from north to south through residential areas.

3.2.2 Surface water flow was described as fast flowing and deepening around low points adjacent to the properties.

3.3 Standing Water 

3.3.1 The majority of surface water from the surrounding catchment flowed to low points to the rear of Woodgate Road.

3.3.2 Surface water that flowed to the rear of the properties first increased in depth within the gardens and against the dwellings.

3.3.3 Standing water was reported to be in excess of 2 feet deep.

4.0 Cause of Flooding  

4.1 In any flood incident there can be multiple factors which result in the flooding witnessed. From the information received, the key factors are:

• The flooding in the Woodgate Road area was caused by intense heavy rainfall beyond the design capacity of drainage systems across the catchment. This led to excess surface water flowing over ground, following localised topography to low points.  
• Long grass cuttings were also reported with the grass having been extremely overgrown and having been cut a couple of days before. These cutting were washed to the gully locations and potentially affected the efficiency of the gully by matting across the top and restricting the effectiveness of the surface water drainage. 
• The Woodgate Road area is situated within a relatively large, predominantly urban surface water catchment area. Underlying topography channels the surface water in a southerly and easterly direction to the low points through the private gardens.  
• There was no prior warning of the location and extent of heavy rainfall, or that the rainfall would be so intense and localised in the affected areas. 
• There are no community or property level resilience measures in place that could have been deployed. 

5.0 Recommendations 

5.1 The following are the Key Recommendations resulting from the flood incident:

• Owners of affected properties should consider preparing a Household Emergency Plan and implementing Property Level Resilience. 
• With support from Flood Risk Management Authorities, the community should make efforts to:  
  • Appoint Community Flood Wardens, 
  • Prepare a Community Emergency Plan, 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• The Lead Local Flood Authority should coordinate with other Flood Risk Management Authorities to extend publicity of the existing information. 
• The Lead Local Flood Authority should work with the community and Local Authorities to assess the viability of options for engineering schemes to reduce flood risk. This might include community level flood resilience measures, improving drainage to accommodate extreme rainfall events, providing attenuation storage areas, and creating formal overland flood flow routes. 

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding occurred to a building, the purpose of which is considered part of the critical infrastructure of the area.

1.2 This investigation was undertaken following the flood incident at Wooldale Road, Northampton that occurred on Sunday 27th May 2018.  

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of Catchment Area 

2.1 The building affected by flooding is located in a surface water catchment area that extends approximately 1200 metres to the north, in a natural valley that extends north through the Lady Hollow Drive residential area.

2.2 The catchment is mixed urban, rural and woodland areas, with approximately 50% developed. The remaining open space includes woodland, agricultural land, playing fields and public open space.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 The rainfall fell on the catchment between approximately 19:00 and 21:00.

3.2 Surface Water Flow 

3.2.1 Surface water flowed from north to south over the catchment, with the cumulative flow increasing in volume as it flowed south and rainfall worsened.

3.2.2 Surface water was conveyed by drainage systems and overland flows to the tributary of Wootton Brook east of Wooldale Road. A lack of capacity at the culverts beneath the access road/roundabout and pedestrian access meant that water could not flow away freely to the south.

3.2.3 The capacity of the culverts was largely restricted by a build-up of debris at the trash screens over the culvert entrances.

3.2.4 The surface water ponded in the area at the west of the car park until it reached a level where it overtopped a ridgeline in the paving between the car park and the affected building. Once this level had been breached, the surface water continued to flow to the building, and access ways on the northwest side.

3.2.5 Water flowed south around the building and access road into ‘V’ shaped external areas and towards doorways, which it then entered.

3.2.6 Water flowed through the building from north to south affecting all rooms set at a low level on the west side of the building.

3.3 Standing Water 

3.3.1 The building affected by flooding is set in a localised bowl, with the levels and gradients of external areas preventing surface water from flowing away from the building or back to the watercourse.

3.3.2 Standing water covered the ground floor of the lowest rooms on the west side of the building. 39 class rooms, the sixth form centre, corridors and ancillary rooms were affected by the flood water.

4.0 Cause of Flooding  

4.1 In any flood incident there can be multiple factors which result in the flooding witnessed. From the information received, the key factors are:

• The flooding in the Wooldale Road area was caused by intense heavy rainfall beyond the design capacity of drainage systems across the catchment 
• Culverts and trash screens on a watercourse upstream of the flood incident restricted the natural flow of water, and this is a specific factor in the cause of the flood incident. 
• The levels and gradients of the external areas around the flooded building directed water to vulnerable areas, with no means for water to flow overground to safer areas. 
• There was no prior warning of the location and extent of heavy rainfall, or that the rainfall would be so intense and localised in the affected areas. 
• There are no community or property level resilience measures in place that could have been deployed. 

5.0 Recommendations 

5.1 The following are the Key Recommendations resulting from the flood incident:

• Owners of affected properties should consider preparing a Household Emergency Plan and implementing Property Level Resilience. 
• With support from Flood Risk Management Authorities, the community should make efforts to: 
  • Appoint Community Flood Wardens, 
  • Prepare a Community Emergency Plan, 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• The Lead Local Flood Authority should coordinate with other Flood Risk Management Authorities to extend publicity of the existing information available. 
• The LLFA should work with the community and Risk Management Authorities to assess the viability of options for engineering schemes to reduce flood risk. This might include community level flood resilience measures, improving drainage to accommodate extreme rainfall events, providing attenuation storage areas and creating formal overland flood flow routes. 
• Local Authorities, Emergency Services and other relevant response groups should continue to work together, and review their immediate and follow up response to the emergency. 

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding of more than five residential or commercial buildings in close proximity occurred during a single incident.

1.2 This investigation was undertaken following the flood incident at Wootton, Northampton that occurred on Sunday 27th May 2018.

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of Catchment Area 

2.1 The affected area of East Hunsbury is located in a surface water catchment area that is bounded by Grangewood Park to the west and Penvale Park to the east.  

2.2 Grangewood Park is a natural valley that runs north to south, between the Tesco Supermarket site on Clannell Road and Rowtree Road.

2.3 Penvale Park is another natural valley that runs east to west, between the site of Wootton Police Headquarters and Hilldrop Road.

2.4 The catchment is predominantly urban with approximately 80% developed with the remaining as open space.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 The rainfall fell on the catchment between approximately 19:00 and 21:00.

3.2 Surface Water Flow 

3.2.1 The main flows of surface water were from north to south from the Green Lane area through private gardens onto Berry Lane. From Berry Lane the surface water continued through private gardens to Villagers Close.

3.2.2 Surface water flow was described as fast flowing and deepening around low points adjacent to the properties.

3.3 Standing Water 

3.3.1 The majority of surface water from the surrounding catchment flowed to a low point on Walkers Way and to a depth of approximately 300mm.

3.3.2 Surface water that flowed to the rear of properties on Green Lane, Berry Road, Villagers Close and Farmers Close and increased in depth against the rear of the dwellings.

3.3.3 Surface water increased in depth across the road and to the front of the properties in Walkers Way

4.0 Cause of Flooding  

4.1 In any flood incident there can be multiple factors which result in the flooding witnessed. From the information received, the key factors are:

• The flooding in the Wootton area was caused by intense heavy rainfall beyond the design capacity of drainage systems across the catchment. 
• Garden structures in the form of walls, fencing and gates in effect became damming structures holding back the surface water flow, this in turn led to a significant build up of water behind them before they either failed, or were broken down to release the water. 
• The Wootton area is situated within a relatively large, predominantly urban surface water catchment area. Underlying topography channels the surface water in a southerly direction to the low points through the private gardens. 
• There was no prior warning of the location and extent of heavy rainfall, or that the rainfall would be so intense and localised in the affected areas. 
• There are no community or property level resilience measures in place that could have been deployed. 

5.0 Recommendations 

5.1 The following are the Key Recommendations resulting from the flood incident:

• Owners of affected properties should consider preparing a Household Emergency Plan and implementing Property Level Resilience. 
• With support from Flood Risk Management Authorities, the community should make efforts to: 
  • Appoint Community Flood Wardens, 
  • Prepare a Community Emergency Plan, 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• The Lead Local Flood Authority should coordinate with other Flood Risk Management Authorities to extend publicity of the existing information available. 
• The LLFA should work with the community and Risk Management Authorities to assess the viability of options for engineering schemes to reduce flood risk. This might include community level flood resilience measures, improving drainage to accommodate extreme rainfall events, providing attenuation storage areas and creating formal overland flood flow routes. 

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding of properties has been experienced on more than one occasion in the last 5 years.

1.2 This investigation was undertaken following the flood incident at High Street and Rose Hall Lane, Middleton Cheney that occurred on Thursday 31st May 2018.

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Site Location 

2.1 Middleton Cheney is a village situated in the southwest of Northamptonshire, approximately three miles east of Banbury town centre.

2.2 One affected property is located on Rose Hall Lane in the east of the village. The other affected property is located at the junction of Main Road and High Street towards the west of the village.

2.3 The centre of Middleton Cheney is a localised high point in the surrounding topography, which falls to the southwest and southeast to two separate watercourses. These flow south out of the village to a tributary of the River Cherwell.

3.0 Summary of Impacts and Findings 

3.1 Rose Hall Lane 

3.1.1 It was reported by the resident and neighbours that surface water flowed south into Rose Hall Lane from Main Road at the northwest. This was observed as a fast rushing water flow.

3.1.2 The flow of water exceeded the capacity of road gullies on Rose Hall Lane, causing these to fill and become unable to accept any further inflow of water.

3.1.3 The area of Rose Hall Lane directly adjacent to the affected property is a localised low point where water settled and increased in depth.

3.1.4 The water at depth against the external wall of the affected property seeped through voids in the stonework to the internal areas of the property. This then flooded the kitchen and summer room floor.

3.2 Main Road/High Street 

3.2.1 Heavy rain caused ponding to the roads and footways around the Main Road/High Street junction. Road gullies were unable to remove the volume and intensity of surface water in the area.

3.2.2 The depth of water increased until flood water entered the cellar of the affected property via the walls, and the cellar door.

3.2.3 There was flooding to external areas of the property, in the courtyard at the side facing Mansion Hill. This built up against the doors with some manageable ingress of water to internal areas.

4.0 Cause of Flooding  

4.1 In any flood incident there can be multiple factors which result in the flooding witnessed. From the information received, the key factors are:

• The flooding that occurred in Middleton Cheney was caused by localised heavy rainfall. Drainage systems were unable to collect and convey rainwater effectively to larger watercourses downstream. 
• The affected properties are located in areas deemed to be at risk of surface water flooding due to the localised topography. 

5.0 Recommendations 

5.1 The following are the Key Recommendations resulting from the flood incident:

• The affected property owners should consider preparing a Household Emergency Plan and implementing Property Flood Resilience. 
• With support from Flood Risk Management Authorities, the community should make efforts to: 
  • Appoint Community Flood Wardens, 
  • Manage surface water run-off to watercourses from the catchment area. 
  • Explore options for funding and contributions for schemes to manage surface water and flood risk. 
• With support from other Flood Risk Management Authorities, the Highway Authority should continue to work with the community and land owners to identify ownership and maintenance responsibilities for drainage systems accepting runoff from the public highway. They should also consider areas where specific highway works could reduce flood risk to private property in exceedance events. 

1.0 Introduction 

1.1 David Smith Associates (DSA) have been appointed to undertake this Section 19 Flood Investigation Report on behalf of the former Northamptonshire County Council (NCC). Internal flooding has been reported at a residential property on more than one occasion in the last five years, warranting this investigation.

1.2 This investigation was undertaken following the flood incident at London Road, Braunston which occurred on Sunday 26th August 2018.

1.3 This document comprises and anonymised summary of the full Section 19 Flood investigation Report for the publication.

2.0 Description of catchment area 

2.1 Braunston is a village situated in the west of Northamptonshire, approximately four kilometres northwest of Daventry town centre.

2.2 The Grand Union Canal and associated marina are located to the northeast of the affected property and the A45.

2.3 The A45 London Road to the front of the affected property is deemed to be at medium to high risk of surface water flooding. Areas surrounding the property are deemed to be at low to medium risk of surface water flooding. Both areas are unlikely to flood from rivers (Flood Zone 1).

2.4 A tributary of the River Leam flows east to west under the A45, at the low point approximately 140 metres northwest of the affected property. The ditch in the north verge flows towards this tributary.

3.0 Description of the Flood Event 

3.1 Rainfall 

3.1.1 Rainfall data from the Braunston rain gauge indicates that 8.6 mm of rain fell from 09:00 to 14:00 on 26th August 2018.

3.1.2 Although this is not considered a particularly high level of rainfall, but the data indicates that there were short periods of more intense rain within the five-hour period.

3.2 The A45 is kerbed throughout with limited means for water to run-off to adjacent land. In heavy rainfall events beyond the design capacity of road gullies and receiving drainage systems, a cumulative flow is likely to develop in the carriageway which would flow northwest to the low point.  

3.3 At the vehicular crossing near the affected property, surface water flowing in the south carriageway channel overtopped the dropped kerbs. The water flowed across the footway, and onto the driveway of the property.  

3.4 The resident clarified that the main contributing flow of water was from the carriageway at the specific dropped kerb location, rather than from the footway or any other dropped kerb nearby.  

3.5 Water flowed down the driveway and into the sunken garden to the rear of the affected property. Here it increased in depth against the rear of the house and entered internal areas of the house via doorways.

3.6 The depth of flood water within the property rose to approximately 150mm. Three rooms in the downstairs area were affected.  

3.7 Sandbags were used, to prevent the flow of water entering the house but this was unsuccessful. An attempt was made to use a pump to lower water levels in the house, but the pump did not work properly.  

4.0 Cause of Flooding  

4.1 In any flood incident there can be multiple factors which result in the flooding witnessed. From the information received, the key factors are:

• Intense heavy rainfall in a short period – causing ground saturation. 
• Surface water drainage systems and watercourses were unable to collect and convey rainwater effectively. 

5.0 Recommendations 

5.1 The flooding that occurred in Braunston was caused by localised heavy rainfall. Drainage systems were unable to collect and convey rainwater effectively to safe areas. This led to excess surface water flowing over ground and following localised topography to low points around a private property.

5.2 To prevent the same levels of detriment in the future, the following should be undertaken:

• LLFA to continue work with the community and Flood Risk Management Authorities to: 
  • Manage surface water to provide a better standard of protection to Highway infrastructure, and the community. 
  • Identify further surveys, investigations and studies required to locate and record existing drainage systems. 
  • Identify all legal responsibilities for drainage and watercourse maintenance, reminding relevant parties of these responsibilities.  
  • Assess the requirement and viability of engineering schemes to ensure the existing infrastructure operates as intended, and to provide a better standard of protection if required.  
• Increase their preparedness to flood events through implementing: 
  • Emergency Plans 
  • Business Community Plans 
  • Property Level Resilience