Storm Surge 2013 : One Year On - Part One : Modelling the Surge

by @cloudskinner

This is the first post of a four week mini-series looking back at the storm surge of 5 December 2013. The surge caused extensive flooding along the East Coast of the UK but our focus has been on the area immediately around the Humber, and you can read our reaction shortly after the storm surge in this older post. Over the next few weeks we will be discussing the research that has been ongoing since the event, how it affected and continues to affect local residents and businesses, the community resilience that has been built and finally we consider the damage done to Spurn Point and its potential future.

This week the focus will be on a paper recently published by myself, colleagues at the University of Hull, the Association of British Ports (ABP) and the local Environment Agency (EA), which stemmed directly from the storm surge. The paper is free to view until 28 March 2015, after which you will require a subscription to Estuarine, Coastal and Shelf Science to view.

Hull's flood defences overtopping on 5 December 2013 (by @tom_coulthard)

Estuaries are very complex environments. There is a lot going on, beginning with the inputs of often several rivers, and the sea in the form of tidal flows. The relative influence of these on when and where the water and sediment moves in the estuary depends on the tidal cycle and the discharge levels of the rivers. It is a to and fro tug of war between these for influence within the estuary.

If that was not complex enough, there are secondary flows within the estuary. River water is fresh and sea water is salty, making the two flows a different density along with water that is mixture of the two in between. The two water types are often different temperatures too, again resulting in different densities and inducing flows from more dense to less dense regions. All of the flows are influenced by Coriolis forces, the deflection of water flow caused by the rotation of the Earth. The shape of an estuary also influences flow, and in combination with the influences above, estuaries like the Humber often show two channels along the bottom - one resulting from tides coming in and one from tides going out. Finally, overlain on these are the winds, waves and pressure influences of the weather.

This makes estuaries very complex and turbulent, and this turbulence can form a layer of thick sediment laden water to form along the bed - this basal mud layer clings to the bottom and effectively lubricates water flows along the estuary and shields the bed from erosion and deposition.  The salinity of the water also causes fine sediment to clump together in a process called flocculation which makes them behave like larger sediment particles.

It is commonly thought that to model the processes in an estuary then you need to account for all of these processes, but doing so is incredibly computationally expensive. It is possible to do, but even on expensive and powerful machines it often takes several days to model a single tidal cycle. Trying to use them to predict the future of an estuary several decades in the future would be almost impossible. Our approach was to use a simpler model, CAESAR-Lisflood, which has been widely used for a similar purpose on rivers for over a decade, to try and model the Humber Estuary successfully without all of this detail.

Animation showing the CAESAR-Lisflood model simulating the 2013 storm surge and associated flooding.

It was during this process when the storm surge struck and the focus of our research switched. We had already tested the model's ability to reproduce tidal flows - rapidly and at small timescales - so we soon tried applying the data recorded by ABP during the surge. This showed that the model could also reproduce the location and extents of the flooding on that night. This was using the latest information on the Humber's flood defences provided by the EA. The quickness of the model to process the data would make it suitable for producing numerous possible scenarios based on live and forecast data, and potentially help predict the extent of future flooding before it occurs.

This work is ongoing. Next week I will highlight how local residents and businesses were affected by the flooding, as discussed at the Humber Conference of December last year. If you wish to view this paper you can do so here.

Skinner, C. J., Coulthard, T. J., Parsons, D. R., Ramirez, J. A., Mullen, L., and Manson, S., 2015. Simulating tidal and storm surge hydraulics with a simple 2D inertia based model, in the Humber Estuary, UK. Estuarine, Coastal and Shelf Science. 155, 126-136 doi:10.1016/j.ecss.2015.01.019

Environmental Microbiology and Me!

Researcher profile: Karen Scott (@DrKarenScott)

As an environmental microbiologist with a biological background I didn't think I would end up working in a geography department. In fact thinking back to my childhood I never thought I would end up in academia, or geography come to that - to be honest my only memories of geography from my school days involved writing a news article on the Exxon Valdez oil spill and drawing a cross section of the Earth! Having always been fascinated by animals, I grew up wanting to work with them in some way or another (once my dad had burst my bubble about a career in bricklaying not being like an episode of ‘Auf Wiedersehen, Pet’!).

I got a place on a BSc Animal Behaviour and Science course at Bishop Burton College in the East Riding of Yorkshire, which I thoroughly enjoyed. However, I found studying animals less engaging than I expected and instead was drawn towards modules assessing the impact of the environment on them. Developing my skills in this environmental sector made me re-evaluate the direction of my career.

Anaerobic workout in the lab

Once I’d completed my degree I got a job working in a microbiology laboratory testing a wide variety of samples ranging from fresh food to environmental water samples. It was a demanding job with long hours but it had its perks, such as free turkeys for the family at Christmas! After a year of working there I’d managed to save up enough money to cover the fees for a Masters degree. I joined the University of Hull Biological Sciences Department and spent a year assessing the effect of contaminated water on shore crab behaviour.

Thoroughly enjoying my year researching and writing I decided the research route was for me, and that’s when I started looking for PhDs. I picked up another microbiology role, similar to the previous one, while I hunted for a PhD and after a few months of looking I found one back at Hull based in Geography. The project investigated the ability of organic matter to decompose within the drainage system in the City of Hull, in particular studying the microbial community, and assessing if it could be increased in some way (outlined in my earlier blog post). Although the project was out of my area, it was cross disciplinary with biology so with a bit of extra background reading before starting, I was able to hit the ground running.

Nice day for fieldwork at Winscar 

After I completed my PhD, I commenced a six month research position in the department where I was split between two environmental projects. I'm now based in the School of Geography at the University of Leeds for the next 13 months working in moorland management and hydrology. The project enables me to expand my skill set within the environmental area, while allowing me the opportunity to get my teeth into some research within the department, which remains a great passion of mine. While I'm not sure if after this project’s completion I will take my career into industry or remain within the academic sector, I am excited by the opportunities for both that come my way.

The Surge 2013

by Chris Skinner (@cloudskinner)

This blog post is going to talk about the storm surge that swept along the east coast of the UK on the 5th December 2013, last week. Rather ironically, I was going to post about problems in predicting disasters and how we mitigate against these, but this seems more topical and worthy of a post., and I hope to give you a bit of an insight into how a GEES researcher responds to live events relevant to their field.

The surge seemed to catch everyone by surprise. I checked the forecast on the Monday as my in-laws were travelling to Hull from London to visit us on the 5th, and the Met Office app suggested Thursday was going to be quite nice, but a bit windy in the far North-East. The forecast did evolve over the week, but not so much to suggest the conditions that resulted in them passing at least five overturned lorries on their journey (two and a van on the Ouse bridge alone).

On Thursday afternoon, there were warnings of a storm surge – a temporary increase of sea level caused by low pressure and high winds – that would potentially flood coastal towns on the east coast. Our local news focussed on Grimsby and Cleethorpes as being the most likely to be hard hit. Hull was just at medium risk. Myself and Prof Coulthard (my boss) watched the tide rise on the Immingham tidal gauge and compared it to the data we held from the same site during the 1953 storm surge.

The 1953 storm is THE storm when talking about storm surges in the UK. It was big and it caused extensive damage and over 300 people lost their lives. This storm was being billed as ‘the worst since 1953’, yet to our astonishment we saw the tidal gauge go up and look increasingly like it was going to exceed the level recorded back then.

As we were leaving the office, around five thirty, the first warnings started coming in that Victoria Dock in Hull was at risk. I followed the story unfold on Twitter as photos popped up showing the first signs of water overtopping the defences. The Marina also flooded and water spilled out into the Kingston Retail Park, and the home of the Hull Stingrays and Hull’s most versatile venue, the Ice Arena.

Flooding between the Marine and Kingston Retail Park in Hull Photo by @estuary_ecology

The City of Hull held its breath as high tide approached. Only the tidal barrier stood between the surging sea and thousands of properties in the flood plain of the River Hull behind. The tide crept ever upwards, lapping at the sides of the mighty barrier but could not overcome it. But it was close – only 40cm remained of that barrier, built to defend the city after the1953 surge. It had done its job, just. The tide height of 5.8m is a record high for Hull.

The Saviour of Hull! - The Tidal Barrier holds back the tide. Photo by @Tom_Coulthard (This is just one of many great photos).

The sea water eventually receded at Hull.  High tide was later in the inner estuary and badly flooded South Ferriby and Goole. The flooding continued further south, in Skegness and Boston. Another great tidal barrier, the Thames, was also needed to save large areas of East London.

Now that the waters have passed the data is beginning to be collected and analysed. What seemed to take everyone by surprise was the scale of it. Data from the Immingham gauge stopped when the level reached 8.5m*, but from the curve it looks like it would have continued to around 9.5m – 2m above the predicted astronomical tide (from the pull of the Sun and Moon), and over a metre greater than the highest reading from the 1953 storm surge (at 8.4m).

*I don't know why the gauge stopped, most of them did before high tide that night. My guess is that they either reached the top of their scale, or exceeded a threshold where it is assume too high to be accurate - The Immingham gauge stopped at around the maximum of the 1953 tide level.

This is very significant. I don’t think anyone anticipated it. As I said previously, 1953 was THE storm. For the last few months I have been working on a computer model to simulate the flows in the Humber, with one of the aims to be able to predict the estuary’s response to 1953-like events, especially in the face of rising sea levels. Much of the Humber’s defences were built after the 1953 surge so unsurprisingly the model showed they coped well. Our hypothesis was that the rising sea levels on top of that might cause them some issues, so we wanted to try and model that.

Naturally, first chance on Friday we ran our model with the tidal heights recorded on the evening before. Our model suggests that if we had been able to predict the scale of the surge we could have anticipated the flooding, even just based on this preliminary data (although a large pinch of salt is needed when interpreting the simulation below).

As bad as the flooding was, it has to be said that our infrastructure did a fantastic job. The scale of this surge was unprecedented, quite a bit bigger than 1953, yet there has not been the devastation, and thankfully, the loss of life that followed that storm. If it were not for structures like the Hull Tidal Barrier, it would have been much, much worse.

And that leaves us with a warning. The International Panel for Climate Change (IPCC), uses different models to try and predict future sea level rises for the next 100years, and the 'Best Case Scenario' - where greenhouse gas emmissions are cut immediately - would likely cause a sea level rise of 40cm. This is the capacity left over on the Hull Tidal Barrier. When we consider that an increase of 60-80cm is probably a better estimate, the ability of our infrastructure to manage this size of event in the future needs to be considered. It maybe that this storm surge is an event that won't be repeated in our lifetimes, but it now stands as THE storm we’ll be using the measure future resilience and it pushed us right to the edge.

Down the Microscope - Understanding urban drainage post 2007 Hull floods

By Dr Karen Scott (@DrKarenScott)

As an environmental microbiologist I spend quite a bit of my time elbow deep in muck collecting samples to be analysed in the laboratory – which is exactly how I spent the majority of my 3.5 years PhD investigating sustainable solutions for urban drainage.

One of the streets during the Hull 2007 floods.

My research came as a result of the 2007 Hull floods, where the city was severely hit by a major flooding event which caused millions of pounds worth of damage. Blocked gully pots were partially blamed for exacerbating the flooding in the city and although it turned out there were other factors behind the severity of the floods, it did cause us to wonder what exactly was going on within the gully pots and whether the waste collected could  be managed in a more sustainable way.

Gully pots are small sumps in the roadside gutter and are important components of the urban drainage system with over 17 million in use across England and Wales, approximately 73,000 of these in Hull. Their main purpose is to collect sediment from road runoff, organic matter and litter before it enters the drainage system where potential blockages could occur. Due to the large amount of materials they collect they require regular cleaning to prevent the pots themselves becoming blocked.

A. Diagram of a large square gully pot. B. Inside the gully pot showing waste collected within.

Despite their importance, gully pot internal processes (in particular decomposition rate of their contents, which may have a significant effect upon the frequency with which the pots require emptying) have received little scientific study in this area. Due to this, it was firstly essential to examine the contents to gain a basic understanding of the processes and to establish the decomposition characteristics of the contents. Understanding the processes that occur within gully pots and determining if the environment affect these processes, is an important element in developing sustainable solutions for managing the pots.

This introductory section of my research aimed to create an initial understanding of the physical and microbial processes within the gully pot waste, the ability of it to decompose, and whether season and geographical locations affected it. To assess this, two lots of experiments were set up - in the field and in the laboratory. In the field, the city of Hull was divided into four main areas – industrial, residential, busy road and areas with high foliage. Gully pots from these four areas were randomly sampled on a monthly basis over a year (which allowed for seasonal differences to be monitored).

Modelled laboratory composting experiment

In the laboratory a composting style experiment was set up over a five week period and monitored on a more regular basis. As the decomposition processes in gully pots are unknown composting methods were used as it’s a better characterised environment and had visible similar organic waste. Setting these up in the lab made it easier to sample, control the environment (I could make sure the temperature, waste level and moisture remained constant/recorded) and ensure the samples would not be tampered with (be that people or weather etc). For all of the field experiments, samples were taken from each gully pot and taken back to the laboratory to be analysed for enzyme activity (which can indicate microbial activity, quality of organic matter and the ability of degradation), organic matter (can indicate how much of the waste can decompose) and pH. The composting trial was only analysed for organic matter to see if it was possible for the waste to decompose.

The finding from the one year field study showed that area had more of an impact than season. Differences in organic matter was observed in the seasons where it was higher in summer (potentially due to high land use e.g gardening which would decrease when the weather got worse and leaf fall during the late summer months) and lower pH in autumn and winter. These differences did not appear to affect the enzyme activity, where similar activity was observed across the seasons. Looking across the geographical area types, organic matter was considerably lower in industrial areas (due to the lack of vegetation) and pH was higher (potentially due the dumping of industrial detritus, such as cement, which was observed in samples). Enzyme activity was higher in samples with higher organic matter values, it was also present in the samples with less organic matter, but just at lower levels.  The results from the five week trial showed that the contents from the gully pots are able to decompose in modelled laboratory environments. Organic content decreased at an average rate of 0.1g of organic matter per 13g of organic matter per day. Although the rate of decomposition was observed to be slow it quantifies a previously unknown degradation process.

While significant differences in the parameters monitored between gully pots were recorded, it was difficult to show any distinct nature of the different gully pot contents. Therefore, it may be possible to treat gully waste in a homogenous manner, rather than individually, especially in a seasonal context. This may greatly assist future research to determine the activity of the contents via replica systems in a laboratory or otherwise, and can be used as a baseline when examining sustainable solutions for urban drainage waste
management.

Scott et al., 2012. An initial appraisal of waste decomposition by microbial processes within roadside gully pots. Waste Management and Research. 31(8). 
This paper can be found here.

The Road to Graduation

Phinally Done

By Dr Karen Scott (@DrKarenScott)

On the 19th December 2012 I submitted my PhD thesis. 6 months and 20 days later and I have just graduated! The process in between these two dates was most surreal, with a never ending feeling about it. Until yesterday!

My research focused on investigating sustainable solutions for roadside gully pot management, which came as a result of the 2007 Hull floods. The fortnight leading up to my thesis submission was one of the most stressful and tiring times of my life, but the massive feeling of accomplishment I had when I handed those two large copies in was overwhelming. After the celebratory buzz (and the hangover) settled down, it quickly sank in that the PhD process was still not over, and wouldn’t be for a while. Not until after the Viva Voca. And then the corrections. 

This was the strangest feeling, the thing which I had been so focused on and had taken over my life for the past three and a half years was written up, bound and handed in, all my lab work was completed and my bench space cleaned, but the process was not finished. It was now in the hands of the gods (or the Professors that were marking it). I felt a little lost to be honest, like all PhD researchers I had got into the system of thinking of nothing else but the PhD, thankfully I had the gluttony of Christmas and New Year to take my mind off this.

When I returned to uni I bumbled along trying to get back into a ‘normal’ routine. My time was filled doing bits of work on a new paper and applying for jobs. The false feeling of it being over snuck in, then I received an email with the Viva date.... and the stress twitch came back. 

I had one month until the exam. I spent the first two weeks trying to work out how to prepare for this thing which had terrified me since the day I had signed up to do the PhD. Eventually after asking just about everyone in (and out of!) the department, I started to revise my thesis, the area around it and anything else I could grasp at.The day came incredibly fast! 

My hands were clammy and my mouth was dry, and this was just on the approach to the department. I was absolutely terrified! My examiners were lovely, they tried to relax me at the beginning with compliments, easy introductory questions and questions about my finds while sampling (bowling balls, money and plastic Gary Lineker legless toys seemed to raise a smile). Then the real questions came, quick and fast. Thankfully I was able to answer most with confidence but there were some hairy times where I felt I was just digging myself deeper into holes. After about two and a half hours they called an end to it, and I was sent out while they made their decision. I went to wait in my supervisor’s office (who looked like a new parent waiting for his first child to make an appearance) and although I was only out for 10 minutes it felt like it lasted longer than the Viva itself! I was called back in to smiling faces, as I was told I had passed with minor corrections. I was over the moon! The celebrations started straight away but I found myself being so exhausted from the whole thing I had to head home for an early night and resume the celebrations on the next day!

After a week of soaking it all in that I had actually passed, it dawned on me it still wasn't over, there were the corrections to do. Thankfully I only had minor corrections, which didn't take too long, but it did take a while to get my head back into it and get them done for the summer graduation deadline. As you can guess from this blog, I made it. It’s officially over. I’m finally done. There is no more work to do, apart from squeezing one or two more papers from the thesis and then put it on the shelf to gather dust. And that feels amazing. Knowing all the ups and downs, late nights, early mornings, retests, retrials and re-jigging of work was worth it, and collecting that piece of paper amongst the rest of the graduates who have all been through this makes it that much sweeter.