Urban Flooding: Why It’s Mostly About Surface Water, Not Rivers.
If you were thinking this is all as simple as ‘elevation’, (how much above sea level), with the logic that places that flood are lower than places which are higher - sadly it’s just not that simple with Surface (Pluvial) Water. And why I think a ‘hyper-local’ set of data is needed…
Images: Residents who are concerned about Surface Water Flooding, or who have suffered flooding in their homes already. Although consent forms were gathered, I’ve pixelated anyway. Unpixelated are people from Waltham Forest Councillors, and Flood Forum, meeting to discuss plans with residents.
I live in the Lloyd Park area of the Waltham Forest borough, and technically this elevation is about 15-20m above sea level. In 2021, there was some pooling water in roads during heavy rains, and long-story-short, after myself and local residents requested the Drains and Gullies be unblocked, cleaned, and repaired by WF Council and Thames Water Authority, (a lengthy process needing a united effort). In short, we had observed more reports of street flooding and it seemed wise to take a pre-emptive measure - ie ‘make a fuss’ now (!) to get things working optimally again. I don’t want to jinx things, or speak too soon, but even a non-technical person can figure out that blocked and broken drains are not going to help in a downpour.
Image Credits: Topographic-Map.
Unfortunately, the same was not true in Wood Street, only around 1 mile East of where I live. The flooding, (as shown below) was serious enough to cause major disruption to infrastructure and housing, although thankfully no loss of life. However, what is perhaps most perplexing is that Wood Street is higher above sea level than Lloyd Park, so one would have assumed it would be ‘better off’, but oddly in recent years, it’s not that straightforward.
If this were only about River (Fluvia) Water, then it would be mostly a debate around Elevation above Sea Level, but evidently, it is more complex than that, and a combination of the sheer amount of tarmac and concrete may be a differentiating factor, as well as the differences in not just the capacity of the underground [combined] drains and sewers, but also how well the drains and gullies are cleaned and maintained, make this a multifaceted problem.
Image: Wood Street and other areas were badly affected in 2021, and this prompted local groups to request meetings with their local Council (as shown above) to demand pre-emptive work now, rather than have to ask after they had been flooded!
(If you are reading this, and are concerned, I can only recommend creating a small email group of citizens and putting forward a collective action request. The saying of ‘stronger together’ is evidently true).
The Difference Between Gullies / Drains, and Council / Water Authority’s Duties?
Being honest, I was not particularly worried about being flooded in my area, but as an Engineer, there is something about illogical bureaucracy and bad websites that is enough of a pet peeve that I can’t leave it alone - and particularly when less-technically-inclined folks are left feeling ignored, confused and neglected by Council and Water Authority. So if you have pedantic technical tendencies, this is arguably a good place to channel them, as the pensioners, parents and non-technical folks in your street will likely need your help.
It is hard not to feel that as both Council and Water Authority do not make it easy to understand. So after about 6 months of reading into the matter, (At the same time, I might have been less dogged if RS DesignSpark were not paying me to do the R&D on this!), hopefully, this will help you or people you know make sense - and then take action!
As is often the way, big organisations are often guilty of a ‘pass the buck’ or ‘computer says no’ culture, but I would also say that within any large group, there are some individuals who do go beyond the apparent bare minimum - and I’m truly grateful to those (on both sides) who did help me and others eventually, even if my overall conclusion is that both organisations are left wanting on making it simpler to resolve issues and to take serious pre-emptive requests if they are to consider themselves truly ‘public servants’ or ‘public services’. So this is a ‘Rant-for-Good’ if you like, and hopefully gives some assistance to reducing (I cannot promise solving) any Surface Water flooding risks…
Who’s Drain is it Anyway?
Chances are, as a general member of the public, you’ll find yourself staring at this blocked ‘drain’ on the left image, and wondering why the other one on the right image is flowing, even though it’s only on the other side of the road (see video).
Image: Excerpt from video, first Gully not draining, despite being on the opposite side of the road to the one that is draining in moderate rain. Something is blocked below the road most likely.
The first mistake you’ve made is calling it a ‘Drain’. It’s actually called a ‘Gully’... so like me, if you don’t know the difference, you’re going to go through ‘call-centre hell’ numerous times. (Oh and the red paint means it’s been ‘serviced’ by the Council… don’t even get me started).
Read this first!
i) So you call the Council, and tell them “I’ve got a blocked Drain”.
They will likely tell you (as mine did) that “Drains are fixed by the Water Authority, not the Council”.
(You’ll likely be fobbed-off, as you don’t know the specific terminology!)
ii) So next you call the Water Authority and tell them “I’ve got a blocked Drain” adding “The Council told me to call you”.
The operator will ask a few questions, like “Is it the thing by the pavement, with a grill over it” - you’ll of course say “Yes - it’s blocked!”... “Aha” the operator will tell you, “That’s Actually a Gully - not a Drain - so that’s the Council’s job to fix it, sorry we cannot help you”. If you now look on their website, you’ll see they are ‘right’, but why - it makes no sense! You just know the hole in the road isn’t letting water go in it and away. Simple, right?!
Images: Excerpts from Thames Water (Water Authority) website, showing the nuances of what they do and don’t do. Nice graphics, but not so easy to follow in practice.
iii) So once again, losing the will to live, you call the Council back again, (and god-forbid, don’t you say ‘Drain’ again, or you’ll be back to square one). It is worth pointing out, how on earth would a member of the public know if the blockage is in the Gully, or in the bit further away, in the Drain. You see why both sides use this lack of familiarity with infrastructure / engineering terminology to bamboozle the public. Or if they don’t, they should be more aware that to the public ‘Gully and Drain’ are used interchangeably, and should not be penalised for the imprecision.
iv) So you specifically tell the Council “I’ve got a Blocked Gully”. This time they are obliged to send someone out to have a look. If asked “Are you sure it’s the Gully and not the Drain?” you’ll have to insist, or this will go back-and-forth forever. Some elderly / non-techy neighbours I spoke to experienced this very ‘loop-of-pedantry’, and as they do not have a good camera or an endoscope, they’d have no way of proving this. [Nor legally speaking should you stick things down roadside drains].
I personally think this is the worst of ‘red tape’, as like something out of a Douglas Adams’ sketch, this is not trying to make it easy to resolve for the average member of the public. The first question should be ‘describe the issue’, not playing jargon-based games.
v) So the Council will come out to take a look. This is where you are somewhat at the mercy of the operators, as they will check that the drain ‘flows’, but their definition of flows is tested with a water pipe, which although more gushing than a garden hosepipe, is not simulating a flash-flood.
Images: The Council contractor said it flowed ‘enough’. Enough to be considered ‘working’. The fact that it didn’t flow in heavy rain was not necessarily their problem to tackle, as he suspected it was likely backed up by silt and the issue is with the ‘main’ Drains…
vi) So back to the Water Authority again (at this point frankly quite enjoying the level of farce the situation had gone to, and knowing this will be written up as a blog). As with the ‘Gully vs Drain’ nonsense, I now ‘unlocked’ a new technical term - which eventually broke the deadlock…
The Council contractor was correct that the ‘Main Drain’, the really big pipe under most roads, was likely full of silt, but what he didn’t say was that the ‘Connecting Pipe’ from the Gully to the Main Drain was the Councils (ie his) responsibility. One thing you learn about both of these groups is that they never ‘lie’, but they just don’t offer up the ‘truth’ easily.
So now I had the next ‘secret level-unlock code’ in this exceedingly dull game…
Image: At this point, these companies didn’t know who they were dealing with - by golly - I got my son’s pencil crayons out and drew this masterpiece of cross-sectional engineering! Image Credits, Jude Pullen, Age 40 ½ .
vii) So now I spoke with the Council once more, and explained that the Main Drain was ok, and hence water flowed slowly, but the Connecting Pipe (their duty to clean) was half filled, and this was what was causing the ‘back-up’ during a surge of water in a flash-flood of surface water. Seemingly this meant they dispatched a crew to ‘jet wash’ the Gully and Connecting Pipe - and presto - it’s worked fine for 2 years now, even in really heavy rain.
This also meant the Council’s suggestion of it being a ‘mid point’ issue of the dip in the road, was also not the case. What bothers me is not that that was not the end reason, but that more time was spent giving suggestions which absolve them of doing anything - on both sides. It required a near forensic level of detailing, and a level of exactness of terms which even as a chartered engineer I found maddening, and all for what?
So the question remained - why did these two organisations give me, and of course many other people, the ‘run-around’...?
Why All The Fuss and Feuds?
As much as I stand by that most of my calls and emails with Council and Water Authority were at best unnecessarily complex, and at worst cynically unhelpful, I wanted to again redress that some individuals (when happened upon by chance, or escalated high enough) were helpful and I would not have been able to
a. Clean my Gully/Drain system, and
b. Learn more about how this whole thing works without them!
The Thames Water Authority (essentially responsible for the big pipes underground) is in clearly bad shape, with around £60 million of debt and seemingly endless operational issues.
Some Councils too are under similarly precipitous management, with Birmingham, Nottingham and Woking Councils all recently in the news for going bankrupt. One can only presume that both companies are not looking to do any work they can possibly avoid.
Going back to this diagram, one has to wonder why on earth the Gully is done by one organisation and the Pipes/Drains done by another? The problem certainly has a lot to do with the privatisation of the Water Services in the late 1980’s under the Thatcher Government in the UK. One Guardian quote called it “an organised rip-off” and it’s arguably been in disarray ever since racking up £60m of debts, whilst somehow paying out £57bn of dividends.
Image Credit: Unison. (link)
However, as much as I think the local council could do with a better call centre protocol, upon reflection, it really feels as if the Councils have ‘inherited’ the problem/task of Gully Clearing, when in my humble opinion it arguably makes more sense for the Water Authority to manage the whole task of water as soon as it’s hit the ground.
With that said, I can still imagine that there will be frictions, as even if my suggestion were to be in effect, I’ve worked on enough building sites, and low-skilled, low-motivation labour jobs to know that if you wanted to knock a few leaves and a bit of trash in a Gully to save picking it up, it will happen! Although the goal of this project is ‘big citizen data science’, one mustn’t forget that photos of evidence are also powerful ‘tools of change’, and when the Council employs third parties to clean gullies, and they don’t - one can perhaps debate if the crisp packets here might have ‘just fallen in’, or indeed whether it was pushed in by very bored individuals, but a FERN WAS HAPPILY GROWING INSIDE THE GULLY. The photo was emailed to the group with all councillors CC’d, but we had not been told whether the responsible third party subcontractor was given a talking to. To add insult to the matter, this fern is no ‘Dandelion’, and will be at least multiple years old (I worked at a Horticultural Specialists when younger, so I can assure you this Asplenium Scolopendrium is living proof that any timely cleaning contract was not being taken seriously. As a taxpayer it seems reasonable to call ‘BS’ on being told a job has been done when it hasn’t. This along with countless other photos from residents ended up having a desired effect of a notable increase in street cleaning in the subsequent months…sometimes your best weapon is collective action - individually these photos don’t earn many likes on social media, but collectively it could yield something more valuable, in form of activism!
Images: “Fern Gully”, right, and blocked drains and other issues needing maintenance. (Yes, it is a superb pun).
Either way, the irritation of leaves and trash and other debris in Gullies and Drains feels like it certainly isn’t for the general public to have to become ‘detectives’ but rather for these larger organisations to ‘play nice’ and if needs be - establish a joint fund that acknowledges that these two words do overlap but a blocked Gully/Drain needs to be cleared one way or another to ensure flooding is minimised.
The “First 6 Millimetres” Rule - and why it matters in urban areas so much
It was a genuine pleasure to speak to David Harding, from Thames Water, who seems to be everything one would want from an informed and proactive member of an organisation. He has featured on and american PBS documentary, which by sheer chance I found, and it uses Waltham Forest (my local borough) as an example of why flooding in urban areas will increase with climate change, but also to be forthright about what we can do to reduce these risks - both as organisations, and as individuals.
Image: David explains various issues of flooding, lost water courses, and flood-relief innovations. Image Credits / PBS Documentary: https://youtu.be/61KHW5AAZF4
What impressed me most about speaking with David was that he was able to break down why flooding occurs, and how this, especially in London, is because a. We have concreted over many natural waterways which ease water, not to mention reducing vegetation in the process, but also b. That we mistakenly build more housing (especially high rise buildings) which have a extremely high output of waste water, sewerage, and indeed all the other strains one finds when dealing with sewerage - if you’re unfamiliar, google ‘Fat Berg’ and realise why you really should not put fat, hair, sanitary products and other not rapidly biodegradable items down the sink/toilet. As much as I am acutely unimpressed with the organisational handling or flooding matters, this does not absolve us, as general public, of having to make some better choices in our lifestyles if we want this issue to be curtailed in its impact.
All these factors mean that much of the surface water devastation is often attributed to the first 6 millimetres of rain that fall. If this can be managed (ie swept away through clear gullies, pipes and drains, which councils have cleaned, authorities have maintained, and public have not mis-treated), then the ‘surge’ which often suddenly floods homes, can be significantly reduced.
Aside from the infrastructure, David also explains how the second key part of dealing with this ‘flash flood’ risk, in the 6 millimetre downpour, is of course by re-establishing more green spaces. Given that a mature tree can absorb 450 litres a day, it’s easy to see why our local parks, headrows, landscaped areas all add up to help reduce flooding in those first critical few moments. David expands on this in a two part interview, and I’ve summarised a few highlights below also.
Interview: David Harding from Thames Water.
Part 1: https://www.youtube.com/watch?v=8Gd12kRroHQ
Part 2: https://youtu.be/V2aFSyGo_kQ?si=qjgEmHcDo8x9Znc2
Historical Evolution of Drainage Systems: London's drainage infrastructure evolved organically, leading to a complex and interconnected network of combined (wastewater and surface water) and separate sewers.
Ambiguity in Responsibility: The clear delineation of responsibility for different types of flooding remains a point of contention. While Thames Water manages the main sewer networks, the historical intertwining of these systems with highway drains and property drainage blurs accountability when flooding occurs. This ambiguity often leads to frustration amongst residents seeking solutions.
Increased Surface Runoff: The urban landscape has drastically transformed, with permeable gardens replaced by impermeable surfaces like patios and car parks. This increases surface runoff, overwhelming existing drainage systems and exacerbating flood risks.
Data Collection and Analysis: Accurately attributing the source and cause of flooding is often difficult due to the interconnected nature of the drainage system. The lack of real-time data collection during flooding events further complicates analysis and hinders effective preventative measures.
The "First Six Millimetres" Concept: David emphasises the importance of managing the initial surge of rainwater. He highlights that even small individual efforts, like utilising water butts and maintaining permeable gardens, can collectively alleviate pressure on the system during heavy rainfall.
The Need for a Multifaceted Approach: Addressing urban flooding requires a holistic strategy that includes:
- Sustainable Urban Drainage Systems (SuDS): Implementing SuDS like rain gardens and permeable paving to mimic natural drainage patterns and reduce reliance on traditional pipe systems.
- <">Retrofitting Existing Infrastructure: Exploring options to increase the capacity of existing sewers and implement measures to slow down surface runoff.
- <">Community Engagement and Education: Encouraging individual responsibility by promoting water conservation techniques and highlighting the collective impact of seemingly small changes.
NB - Summary Drafted by NotebookML [AI] from Youtube Transcript. Edited by Jude Pullen.
Blog Series Contents:
Prologue - The Case for 'Hyper-Localisation' of Civic Data
Research & Development:
Part 1: Filling the Local Data Gap
Part 2: Civic Services & User Experience Research
Part 3: Ideation of Flood Alert Concept
Part 4: Prototyping Back-Story
Part 5: Citizen Science Learnings
Open Source Build Guide:
Part 6: Build Guide for 3D Printed Assembly
Part 7: DIY Decals for 3D Prints
Part 8: Code & Data Guide
Future Ambitions:
Part 9: Project Reboot with Machine Learning
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