**Document:** Flood Risk Assessment Report
**Application:** 19/00081/B — Installation of replacement front window and rear window and door
**Decision:** Permitted
**Decision Date:** 2019-03-12
**Parish:** Malew
**Document Type:** report / flood_risk_assessment
**Source:** https://planningportal.im/a/29565-malew-5-victoria-road-windows-replacement/documents/1330944

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# Flood Risk Assessment Report

## 3. Assessment Of Flood Risk

[Table omitted in markdown export]

![photograph from page 1](https://images.planningportal.im/2019/01/219714.jpg)

### 3.1 Flood history

Information on the property-specific flood history has been collected through discussions with the owners of the property.

The homeowner reported that the cellar floods on a regular basis, the last time being Saturday 6th of January 2018. It was reported that water entered the cellar through the floor and walls to an approximate level of 100mm.

January 2002 was reported as being the biggest flood event. The homeowner reported water coming up through the floor of the cellar and seeping through the wall. Flooding reached a depth of approximately 430mm. This level was taken from a mark left on a table leg in the cellar.

In 2014 the road at the front of the property also flood to a level of approximately 240mm, however, the front threshold is approximately 420mm from the pavement level so water did not enter the property at ground floor level.

There is a sump pump currently fitted in the cellar, however, the condition of the pump is unknown.

Currently there is no flood warning service on the Isle of Man.

### 3.2 Flood depths

Modelled flood depths are not currently available for use in this report. Manx Utilities Flood Map shows that this property is at High Risk of River and Tidal flooding. The risk of surface water flooding to the property is unknown, although surface water flooding has not been reported as an issue.

The following table displays reported flood events and depths at this property.

### 3.3 Future increase to flood risk

The global average surface temperature has increased since the late 19th century. Further warming is unavoidable and is being enhanced by human activities. This warming has changed, and will continue to change the water cycle and sea levels, with sea levels predicted to continue to rise beyond 2100.

#### 3.4 Potential sources of flooding

![photograph from page 2](https://images.planningportal.im/2019/01/219716.jpg)

##### Fluvial (River) and Tidal

The property is situated on the left bank of the Silverburn River.

The Manx Utilities Flood Map shows the property has a high chance of River and Tidal flooding in any year. The Flood Map indicates the extent of river flooding associated with a flood event having a 1% chance of occurring in any year and the extent of coastal flooding for the extreme sea level having a 0.5% chance of occurring in any year.

https://www.manxutilities.im/media/1520/silverburn_subset_-1.pdf

##### Surface water

High levels of precipitation increase the likelihood of surface water flooding. The risk of surface water flooding to the property is unknown.

Please note that surface water issues have the potential to be exacerbated by poorly functioning surface water drains.

Surface water flooding will tend to follow road levels resulting in relatively shallow depths of flooding when compared to fluvial and tidal depths.

##### Groundwater

There are no groundwater level measurements available within the vicinity of the site. However, with increased precipitation, groundwater levels will rise, which could result in groundwater entering the property directly through the property floors, and an increased level of surface water overland flow. The property is known to flood.

##### Foul drainage

The property may be at risk of flooding as a result of foul drainage becoming inundated, causing sewage to back up into the property. There have been no reports of poorly functioning drains, or sewage backing up into the property and the property has no toilet on the ground floor.

## 4. Routes Of Water Ingress

![The image displays architectural drawings, including a side elevation of a building with level annotations and a site plan showing property boundaries and ground levels.](https://images.planningportal.im/2019/01/219720.jpg)

### 4.1 Property plan

The plan below shows the outline of the property, with threshold and ground levels.

JHA
consulting

## 4.2 Potential ingress routes

### Doorways

There are 2 external doorways (front and rear) which could potentially present direct ingress routes for floodwater, however, they are raised above ground level and all previous flood levels. The rear door is set at a lower level and leads onto the yard adjacent to the river.

### Flooring

The main section of the ground floor is constructed of suspended wood, the kitchen to the rear of the property is 200 mm lower than the rest of the ground floor and the floor is constructed of concrete. The cellar floor is also constructed of concrete and although it appears to be in good condition it is known to be an ingress route for groundwaters and seepage from the river.

### Airbricks and air vents

There are no airbricks or air vents located around the building perimeters.

### Walls

Although the condition of the external walls of the property and river wall are considered to be in good condition, if flood water were to remain in contact for an extended period of time it may seep through and enter the property. This is especially true for any areas where the pointing and stonework has degraded.

### Foul drainage

Inundation of the foul drainage may cause sewage to back up along the system, resulting in internal flooding, however, no issues have been reported and there is no downstairs toilet.

### Cellar Skylight

The cellar has two skylights, one at the front and one at the rear. The skylight at the rear has been sealed with expanding foam to prevent water ingress. The skylight at the front of the property has a large gap between the wall and the frame which would provide a direct ingress route for flood water should water pond against it. The skylight at the front ground level is raised up approximately 400 mm from ground level, preventing water from ponding against it.

![drawing from page 4](https://images.planningportal.im/2019/01/219721.jpg)

## 5. Impact Of Flood Water

![drawing from page 5](https://images.planningportal.im/2019/01/219722.jpg)

Following the January 2002 flood event, the resident had to replace white goods situated in the cellar. The gas meter and electrical sockets have never been affected by flood water as they are raised above the level of flooding and are located at ceiling height.

## 6. Photographs

![A photograph showing the side exterior of a white building with an open door, steps leading up to it, a window, and a vertical drainpipe.](https://images.planningportal.im/2019/01/7187699.jpg)

Front of Property  Front of Property ![A street-level photograph showing a row of terraced houses in Castletown, featuring a prominent three-story cream building with arched windows. A blue car is parked on the street in the foreground.](https://images.planningportal.im/2019/01/7187696.jpg)

Rear of Property
(showing cellar skylight at ground level and raised access to rear door)

![A grainy photograph showing the rear exterior of a white-washed residential building with a small patio area containing a blue tub and potted plants.](https://images.planningportal.im/2019/01/7187697.jpg)
Front Threshold

![A close-up photograph of a residential front entrance featuring a wooden double door with the number 5, set within an arched doorway flanked by white columns.](https://images.planningportal.im/2019/01/7187698.jpg)
Rear Threshold

Front Cellar Skylight

Front Cellar Skylight

Rear Cellar Skylight

Existing Cellar Sump Pump

![Two interior photographs showing a window in a rough stone-walled room, likely a cellar, accompanied by a drainage report header.](https://images.planningportal.im/2019/01/219726.jpg)

![A close-up photograph labeled 'Front Cellar Skylight' showing a gap or joint between a stone wall and a frame, likely documenting existing conditions for the application.](https://images.planningportal.im/2019/01/219727.jpg)

![A grainy interior photograph showing a room with a window, distressed walls, and a sink area, likely documenting existing conditions for renovation.](https://images.planningportal.im/2019/01/219728.jpg)

![A grainy photograph showing a floor opening with pipes, labeled 'Rear Cellar Skylight' at the top.](https://images.planningportal.im/2019/01/219729.jpg)

Front Cellar Skylight (at ground level)

Front Cellar Skylight (at ground level)

Front Cellar Skylight (at ground level)

Rear Cellar Skylight (at ground level)

Rear wall
(left bank of Silverburn River)

![A high-angle photograph showing a narrow rear garden or yard area featuring a white wall, a red tiled boundary, and a patch of soil with vegetation.](https://images.planningportal.im/2019/01/219731.jpg)

![A photograph showing the exterior entrance of a building featuring stone steps leading to a door and a raised area protected by a black metal railing.](https://images.planningportal.im/2019/01/219732.jpg)

![A photograph showing the exterior of a building featuring concrete steps, potted plants, and a dark window or opening in a white wall.](https://images.planningportal.im/2019/01/219733.jpg)

![A photograph taken from a patio looking out onto a garden area with a large puddle reflecting the sky and trees.](https://images.planningportal.im/2019/01/219734.jpg)

**Steps up to Front Threshold**

**Steps up**

**Gas Meter Located in Cellar**
*(Above height of previous flood events)*

**Electric Sockets Located in Cellar**
*(Above height of previous flood events)*

![A close-up photograph showing concrete steps leading up to a red front door, flanked by white walls and a black railing.](https://images.planningportal.im/2019/01/219736.jpg)

![A grainy photograph showing an exterior entrance area with steps leading to a door, a vertical drainpipe, and a waste bin on the left side.](https://images.planningportal.im/2019/01/219737.jpg)

![Interior photograph showing a yellow gas meter mounted on a rough wall with black piping and a window frame to the right.](https://images.planningportal.im/2019/01/219738.jpg)

![An interior photograph of a workshop or utility room showing a workbench, tools, and a window.](https://images.planningportal.im/2019/01/219739.jpg)

JBA
Consulting

7. PROPERTY LEVEL PROTECTION MEASURES TO REDUCE
RISK

7.1 Introduction

Property level flood protection options have been assessed. The primary intention is to
develop a cost-effective and practical range of property level flood protection options
within the immediate curtilage of the property, to help mitigate and reduce the effect of
flooding.

The focus has been on assessing means to increase the flood resilience of the
property as well as restrict the entry of floodwater into the property (flood resistance)
using proprietary measures available through reputable suppliers. This property is
constructed from single skin Manx Stone with concrete ground floors, and there is a
risk of flooding above the threshold level.

7.2 Design criteria

JBA Consulting surveyed the property to establish the appropriate height to which
flood mitigation measures can be provided.

The Department for Environment, Food and Rural Affairs' best practice guidance for
Property Level Protection states that product selection should prioritise measures
which bear the BSI Kitemark. All BSI Kitemark products have been tested and their
performance confirmed up to maximum depths of 900mm. Research carried out for
the Department for Communities and Local Government (DCLG) and the Environment
Agency has recommended that the use of resistance measures should generally be
limited to a nominal protection height of 600mm above ground level: the lowest point of
ground abutting the external property walls. This is because the structural integrity of
the property may be compromised above this level, which also increases the risk of
cracks and leaks.

It should be noted that the flood mitigation measures described would not be expected
to cause an increase of flood risk to other properties or other parts of the local
community. They will help mitigate against flood risk but, as with any flood alleviation
scheme, flood risk cannot be removed completely. Emergency plans should be in
place that describe the installation of measures but also take note of, and prepare for,
the residual flood risk that remains. Information on preparing a personal flood plan is
provided in section 10.2.

It should be noted that the options described here are outline, for further discussion
and agreement between the owner and appointed supplier/installer. Further
agreement will also be needed with the appointed contractor concerning the specifics
of any installation works. It is the responsibility of the contractor to ensure that all
installations and modifications to the property are compliant with all relevant
regulations, standards and guidance.

7.3 Flood Risk Mitigation Options

The list below presents a number of options the owners could take to reduce the
impact of flooding to the property. The list has been separated into flood resilient
measures and flood resistant measures although a combination of options may provide

![photograph from page 10](https://images.planningportal.im/2019/01/219740.jpg)

## the best way forward.

![drawing from page 11](https://images.planningportal.im/2019/01/219741.jpg)

Flood resilient measures will be effective independently of any other measures employed. Property owners may choose one or more of these measures depending on the preferred use of funds.

The efficiency of flood resistance measures relies on a package of measures being employed to restrict flood water entering the property through the various possible entry routes discussed in section 4 above (note for flood water to enter through the front of the property it is assumed that the cellar would be fully inundated and water is likely to be entering via the suspended wooden floor). Flood resistance measures have therefore been grouped together as one suite of measures with options to protect a particular entry point where applicable (for example the use of flood doors and door barriers).

#### 7.4 Flood Resilience Options

The following is a list of flood resilient repair options that can be considered to help reduce the damage once floodwater enters the property. The primary risk in this instance is flooding to the cellar only to reasonably shallow depths. It is noted that a more significant event could potentially cause inundation at ground floor level. Flood resilience measures for the cellar include:

1. Cellar - Raise white goods off the floor and above the height of flooding.
2. Cellar - Provision of high level shelving.
3. Cellar - Provision of flood bags and/or boxes for storage.

Although the electric sockets are raised in the cellar it is noted that a more extensive flood event may result in greater depths of flooding that could impact the power supply to the building. The owner may wish to consider installing a separate fuse box for cellar electrics
It will be important to continue with any practices for protecting furniture, carpets, electrical goods, personal belongings and documents to safeguard such items in the event that water does enter the property.
In the event of a larger storm event flood water may fill the cellar to full depth and the owner may need to consider the impact of flood water emerging through the suspended wooden floors and via the front a rear door.
Further information is available from: www.nationalifloodforum.co.uk

#### 7.5 Flood Resistance Options

In addition to flood resilient repairs, flood resistance measures can be used to limit water entry into the property.

1. Cellar - Supply and installation of 2 external window barriers. It is noted that the rear skylight is partially buried beneath yard level and it maybe that sub ground level needs to be bricked to prevent seepage. A sealed window or flood barrier could then be used to reduce risk of water inundation. At the front of the property the

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*Data sourced from the Isle of Man public planning register under the [Isle of Man Open Government Licence](https://www.gov.im/about-this-site/open-government-licence/).*
*Canonical page: https://planningportal.im/a/29565-malew-5-victoria-road-windows-replacement/documents/1330944*