Coastal Flooding

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Coastal flooding is caused by high tides, low pressure weather systems and surge conditions caused by strong winds blowing large waves towards the shore. All of these elements are needed to cause a coastal flood be it overtopping caused through spray and splash or more devastatingly, a breach of our defences.

Simply put, a high tide is a body of water that reaches the highest point of the shore. Think of it as half filling a bowl with water, if we gently slant the bowl to one side, the water will rise on the side which is tipped down but lessens on the side that is raised. This is the same for our seas and oceans except that we are not gently slanting the earth from one side to the other, that's a completely different natural force not discovered until one fateful afternoon in Lincolnshire.

So we now know what a high and low tide is but not yet discovered why they occur. For this we need to travel back in time to rural Lincolnshire in the year 1687.

Legend has it that whilst sat in his garden at Woolsthorpe Manor, near Grantham, Lincolnshire, England, Sir Isaac Newton formulated his world changing gravitational theory in 1665/6 after watching an apple fall from a tree. Unlike many people of that time, Isaac wondered to himself why the apple fell straight down rather than going up or sideways from its original starting point. It was then he hit on the theory that all things were affected by this thing called gravity and thus Newton's Law was born.

Up until the point Isaac discovered gravity, the reasons for tides happening had not been considered. There was no real thought behind it except for setting sail on a high tide was easier than a low tide and when it was rough, water was wet and cold!!!

Obviously it took a bit of working out but the mathematics behind Issac's observations proved that there were forces acting upon us that we could not see but affected everything in this world, and that of others. This became known as Newton's Law.

"Newton 's law of universal gravity states that a gravitational attraction between two bodies is directly proportional to their masses, and inversely proportional to the square of the distance between the bodies. Therefore the greater the mass of the objects and the closer they are to each other, the greater the gravitational attraction between them."

Sounds really complicated doesn't it, so lets take a look at it in more detail. Gravity on Earth acts on all objects by pulling them down towards the centre of the Earth, this of course also includes us unless you know a trick to beating it, then please write in. This force pulling down on an object, or you, is equal to the object's, or your weight so the heavier you are, or the object, the more gravitational force will be acting upon you in order to keep us flying off in any direction which could become rather messy.

Gravity affects everything on earth and of course, the other planets that make up the Milky Way be they bigger or smaller than the Earth. The Sun isn't immune to the affects of gravity even though it is 109 times wider than our Earth (the image to the right is for illustration purposes only). In fact you can fit the Earth into the Sun 1.3 million times by volume and to match the Sun's mass, you would need 330,000 Earths. So in the case of the Earth, the Sun's mass is huge but then it is also about 93 million miles away so what gravitational forces do arrive are no where as near as strong as those exerted by our Moon.

Our Moon has a gravitational pull roughly equivalent to 17% of that of the Earth but being only 384,400 miles away, exerts a far greater pull on the Earths oceans and seas. Like Everest, if you are looking for a weight loss plan that has results, then standing on the surface of the moon will see you weigh 6 times less than that eating your ice-cream on Mablethorpe beach. Something to consider, no doubt!

Imagine then, if you will, these forces combining with the Earth's rotation and of the Sun pushing and squeezing the water around the planet forcing them to bulge out on the side closest and farthest away from our Moon, a bit like pushing down on an air filled balloon. It is this bulging that gives us our tides; the greater the bulge, the higher the tide often referred to as a 'Spring Tide'.

But a tide does not make a flood, so lets look at the next element in our recipe for disaster.

Us Brits love nothing more than to complain about the weather; its too hot but its too cold, its too wet when its too dry and of course, don't get us started on the subject of the wrong type of snow! Wind also plays a huge role for us Brits; it dries our laundry, it powers our homes and industry and it shapes our land and seascapes from the pollination of cereal and other food crops to redesigning our shorelines through wave action.

Weather is in fact a series of mixed events occurring every minute of every day in our atmosphere which can change rapidly and vary from one place to another often at the same time. Most of our weather occurs in the troposphere which is the part of our atmosphere closest to the Earth's surface.

These variations in weather occur when air pressure changes. Air pressure is caused by the weight of millions of air molecules acting upon each other which make up our atmosphere.

Have you ever wondered why on hot sunny days there appears to be few clouds in the sky? The answer is less spectacular than you would think. Air flows like water in any direction, when its hot and sunny, air flows down and outwards across the surface of the Earth, more often than not, preventing clouds from forming. It is this downwards movement that gives us high pressure, pressing down on the surface of the Earth including our seas and oceans.

Therefore you safely assume low pressure weather systems are the complete opposite to high pressure in that air molecules rise and blow in an anticlockwise direction, in the northern hemisphere of the Earth, dragging with it cool watery vapour which condenses into clouds, often bringing rain and windy weather.

Air pressure is measured in hectopascals (hPa), also called millibars. The standard average air pressure at sea level on Earth is defined as 1013hPa but this does vary significantly from area to area and season to season. Certainly the highest of highs in air pressure are usually seen during the summer months of the year in the northern hemisphere whilst the lowest of the lows occur during autumn and winter. In the southern hemisphere, summer and winter are opposite to ours.

As we discussed earlier, high pressure pushes down on the surface of the Earth effectively keeping things calm and flat but low pressure causes air to raise decreasing the pressure (depression) on the surface of the water allowing it to increase in height.

Have you ever wondered why a freshy washed glass left on the draining board sucks up water? Well here's an experiment you can do to show you how low pressure acts upon the surface of our seas and oceans.

Equipment needed:

• 1 tumbler, preferably see through.
• 1 bowl of hot (not too hot) water.
• 1 dish or saucer big enough to hold the upturned tumbler

Method

Fill a bowl with hot water, warm enough to place your hand without burning yourself. Place the glass tumbler in the bowl and leave for a couple of minutes. Using your dish or saucer, place a small amount of water in it to cover the bottom. Now place your tumbler face down on your dish or saucer and watch what happens.

Has any water started to raise inside the tumbler yet? If not you may need to warm the tumbler a little longer and then retry. What you are seeing is what happens in nature, you are causing an air pressure change between the inside and outside of the tumbler. Outside is normal atmospheric air pressure pushing down on the surface of the water but because you have warmed the tumbler, you have lowered the air pressure inside the glass causing a vacuum which then sucks up the water.

This is where it gets interesting, we have already said that our normal atmospheric pressure is around 1013hPng acting upon the surface of our seas and oceans so using the experiment above what does this mean to the level of the water if air pressure drops?

On average, for every millibar drop in average air pressure, the level of our seas and oceans raise by approximately 1cm so if you combine this element with the highest gravitational pull of our Moon, and to a lesser affect, our Sun, you start to see why our sea defences are so important! But this isn't our final recipe for disaster, we need just one more element; the wind!

Do you remember we briefly mentioned boiling water at the top of Everest? Well, at lower pressure or high altitude, the boiling point of water is lower. Let us make a cuppa on Mablethorpe beach, here the water in our kettle will boil at 100 degrees centigrade. However, if we now climb Mount Everest and do the same thing again; let's face it, you are going to need a cup of tea climbing Everest, our water boils at around 68 degrees centigrade. It also means you may struggle to boil an egg on top of Everest because the white of an egg cooks at around 85 degrees centigrade, whilst the yolk cooks at 65 degrees centigrade; breakfast may take a while!!!

What exactly is wind?

Wind is affected by air pressure. During the day air above the land, even on cool days, heats up faster than air above water. Unlike air pressure which pushes down or travels upwards, warm air does rise because its molecules are less dense and have a lower pressure associated with them than the surrounding air. Its the same thing that happens when you turn on your heating be it underfloor or traditional radiators. As they get warmer, the air around them heats up rising to eventually heat the room. Cold air on the other hand is denser than warm and so falls which is why you may sometimes feel a chill when sat by a window or door. The same thing happens in nature, whilst the warm air rises up, cold air is forced down and its the interaction between the two forces that causes wind.

This action happens every day of every year and is important for the planet to survive. Wind can sometime prove disastrous; those of you who are old enough to remember the infamous weather forecast during the 1980's which saw a hurricane cross over the southern counties of the UK with devastating affect. Likewise, wind blowing towards the shore pushes water further inland up against our defences but when combined with a high lunar tide, a deep depression in air pressure and the wind coming onshore, we have our final element to our recipe for disaster.

Let me ask you a series of questions and by the end of it, if you can answer yes to any of them then please follow the advice.

1. Can you see the sea from your home?
2. Do you live near the sea?
3. If you live near the sea, what type of property do you live in? A house, a bungalow, a mobile home or something else?

If you have answered yes to either questions 1 or 2, have you taken steps to to safeguard yourselves, your family, friends and neighbours?

Step one. Use the map below to see if you live in a flood warning area or visit the Environment Agency's website  Check the long term flood risk for an area in England - GOV.UK 

How to use the flood warning Map

• To expand the map, click the two outward facing arrows in the top right hand corner of the map window
• To search for your home address, click on the magnifying glass.
• To view flood warning information, click on the purple areas on the map to open a window with further information.

Step 2. Sign up to receive flood warnings either by calling 0345 988 1188 or by visiting  Sign up for flood warnings - GOV.UK 

Step 3. Create a personal flood plan for you home and family. More information about personal flood plans and checklists are covered later but to download a copy please visit  Personal flood plan - GOV.UK 

Step 4. Become familiar with flood warnings and their meanings.

Step 5. Get involved with a local community emergency response team or become a  Ready for Anything Volunteer 

Before we continue to look at what we can do to safeguard ourselves, lets take a quick look around the UK at some events that have impacted us over the past 70 years.

This is just a small selection of flooding events along the east coast but you can find many more examples of coastal flooding both here in the UK and on mainland Europe. Globally, coastal flooding impacts close to 1.5 billion people or approximately 19% of the World's human population. Coastal flooding isn't only caused by storms and we will look at this a little later on in our story.

Lets get back to what else we can do to safeguard ourselves against these types flooding events by taking a look at what a personal flood plan is and what it can do for us.

A personal flood plan is by far the simplest way to prepare for flooding events be they coastal or from rivers or from surface water (flash floods). A personal flood plan can help save time in getting everything right before it happens.

Try to keep your flood plan as simple as possible and make sure everyone in your household is aware of it and where it is stored or displayed. A good place to store it is the fridge door; how many times per day do you visit the fridge?

Do you know where your utility shut off valves are?

Switching off your water supply.

Often you will find your mains water stopcock under the kitchen sink however it may also be in the bathroom in some properties. Wherever your stopcock is located, make sure you know how to turn it off should you need to. Most stopcocks work just like a tap, turning it clockwise will shut off the water supply to your home. It is not always necessary to shut off the water supply but should you ever need to its worth knowing how.

Switching off your electricity supply

It is really important to take care when touching anything electrical. Make sure you have dry hands and NEVER touch exposed wires. On all UK domestic consumer units, be they modern or of the old fashioned fuse wired type, you will find a main power switch. You will need to check which direction the switch travels in to switch off the electricity supply to your home as this may vary from unit to unit. Switch off your gas supply

ONLY SWITCH OFF YOUR GAS SUPPLY IN AN EMERGENCY.

Domestic gas supplies can be sited outside and inside of your property. In either case the process is the same. You will find a lever style handle between where the gas enters the property and the meter unit. Make a note of the position it is currently in as this is allowing gas to flow from the mains pipe outside through the metering unit and into your appliances for use. To switch off this supply simply move the lever in the opposite direction. IMPORTANT. DO NOT SWITCH ON YOUR OWN GAS SUPPLY. It must be switched on by a technician who will perform a pressure test on the system and relight the pilot lights in the home before switching the supply back on.

This is a checklist to get you thinking about where to put things so they don't, as far as practicable, get damaged by flood waters. Work your way through this list to give you piece of mind.

When it comes to evacuation, think about what you may need to take at very short notice such as important personal documentation, medications, pets and of course, your children, if you have any. If they are young children, then you are going to have to think big! Children come with lots of add-ons so it pays to spend a bit of time thinking about these now rather than waiting until the last minute.

Pets too need more things than you first think so again spend a few moments thinking about this. Remember, your pet may also get stressed out by having to leave its home in an emergency so try to bring along a bit of normality for it, be this its bed and/or its favourite toy. Oh and don't forget its food! It is your legal responsibility to ensure your pet is looked after at all times so please be mindful. For more information about taking care of your pets during an emergency click  here 

If you do need to evacuate please make sure you have somewhere to go and if you can, register that you have left your home by clicking on this link. You can find out more information about the LRF self-registration app by following this link.

The important thing to remember is that you should remain calm, take everything you need with you for up to 3 days and be sure you know where to get the latest information on what is happening in your area.

You can select the way that the LRF communicate with you through the app so you can stay informed and know when it is safe to return to your home.

Sometimes it is not always possible to go somewhere familiar when crisis happens and in these times you just need to get somewhere that is safe. Your local authority, as part of the LRF, is responsible for setting up and managing emergency places of safety, often referred to as a rest centre. There are many different types of centre that operate in times of crisis so if you would like to learn more about them, please follow this link.

During live declared emergencies involving a coordinated multi-agency response, the LRF will post live incident information, including open rest centres on its incident page. To navigate to it please click  here.  Once you have arrived at the rest centre you will be asked to register, please follow all the advice and guidance given by rest centre staff and volunteers.

The team at the rest centre will let you know when it is safe to return to your home.

Many people like to come together to form their own community based, emergency planning and response teams working with the LRF to safeguard their community before during and after crisis. This often means that the group may be left to initially start the process of looking after the community for a short period of time; 'the Golden Hour' or until emergency responders arrive on scene. Once there, the community emergency response team work with emergency services to enhance their response and in doing so, speed up the recovery process.

The LRF have a programme of innovation completely free to any community based group in the county, be they associated with a town or parish council or not. To find out more information about joining an existing group or forming one from scratch please follow this link

Community emergency response teams work with the LRF right through to recovery and have access to the county's emergency planning duty officers 24/7 so they always have support to hand.

With nearly 29,000 small and medium sized businesses in the county, business continuity is crucial to ensure your business can continue to operate during crisis, or if not, recovery in a time that meets your businesses needs. A quick internet search will throw up lots of information about what you should do if you are a business and trade within a flood risk area however, the majority of small and medium sized businesses still do not have fully functioning mitigation plans, often referred to as BC plans.

Effectively, a business continuity plan is a business's appetite for readiness to maintain its critical functions after an emergency or disruption. This could be anything from a cyber-attack on your company's IT systems, or as we are discussing here, a coastal flood preventing your company from selling, providing or supporting its customers in the short to medium term. In the worst-case scenario, it could put your business out of business for good if you don't take simple steps to protect it.

If you would like more information on starting a BC plan for your business please follow this  link 

Coastal flooding, in the UK, is caused by a combination of 3 elements coming together that have the power to overwhelm natural and human sea defences. Think of it like a fire, if you remove one element from the fire triangle, fire goes out; its the same for significant coastal flooding, if one of the elements is missing, flooding is unlikely to occur however, never say never...

We also now know what we can do to safeguard ourselves, our families, our communities and businesses through preplanning and, during emergencies, where to obtain the right information, at the right time to get through.

If you would like to find out more about coastal flooding why not check out  Tsunami