Gentle Decline 2/33: Walking and Wading

Hello! This is the first issue of Gentle Decline that’s coming from Beehiiv, and there’s some commentary on that below. But the main bit of this issue is about flood risk assessment. Back in Issue 2/31 (not too long ago), I wrote that “you need to assess how your immediate area is for floods”. Several people wrote in to ask how this actually works, in detail. So I’m going to walk through a process of assessing that, in considerable detail. And it turns out that flooding is still pretty topical!

Also, thank you enormously to the people who made contributions via Ko-fi or signed up for Patreon since the last issue. I appreciate it hugely, and it has made a genuine difference.

[Gentle Decline is an occasional newsletter about climate crisis, and - more to the point - how to cope with it. All issues are free! You can support the newsletter via Patreon (where there’s sometimes further discussion about particular points), Ko-fi, or by buying some of the seriously classy merchandise, including the new Plant More Trees t-shirt.]

Positive News

A soon to be ex-industrial area in Dublin is being converted to housing. Brussels has a roadmap to become a 10-minute city. Renewables are now the cheapest form of power. And Swedish manufactuer Scana have produced a solar truck.

Nazis

This is the first issue hosted on Beehiiv. This is since I’ve moved away from Substack because they support Nazis. I mean, they’ll say they don’t support them, and that they wish they wouldn’t be the way they are, but they’re not taking the simple step of removing them from their service. There’s an apocryphal story about this, wherein if you let one Nazi stay in your bar, you very shortly have a Nazi bar. And I absolutely guarantee that every white supremacist, fascist and general racist asshole on the planet is making a beeline for Substack right now, because there are plenty of places that won’t tolerate them, so that they crowd into the ones that will. I’m annoyed about this; Substack is an excellent platform, and has served all of my newsletters well. But I don’t want to hang out in a Nazi bar, so here we are.

The archives are littered with links that still go to substack; I’ll go back through and clean those up over the coming weeks. I’m aware of some formatting issues that have happened as well, and those should be fixed in around the same timeframe.

Flood Risk Assessment

I had thought about doing a video of this process, but it would either be very long and dull - me walking around a neighbourhood and muttering - or it would be weird and choppy. I don’t really like video, so unless there’s huge demand for it, you’re getting this text version instead.

You don’t need any equipment for this, really, with the possible exception of a phone camera, and some footwear and a coat suitable for wet weather. And all of this assumes you know nothing about the situation already; as noted at the end, local knowledge always beats out my generic instructions.

Maps

The first thing to do is look at a map. Ordnance Survey maps in Ireland and the UK are the best for this - Google Maps are good, but they’re not always accurate for non-road features. One example that I’m familiar with is that a long stretch of the Brosna River is just plain missing from the map, and it shows a number of waterways connecting the river to an old canal (now a greenway) which definitely do not exist now, if they ever did (and given the weird straight lines that don’t align with field boundaries, I have my doubts). Indeed, it shows the greenway as still being a canal. USGS maps will serve in the USA, and there should be some local authoritative map wherever you are in the world. The main features you’re looking for are bodies of water and waterways, both of which are conventionally in blue, and contour lines (also not shown on Google Maps).

Find where you live on the map, and determine what’s uphill and downhill from you. You do this by looking at the contour lines, and drawing a line (imaginary will do) at approximate right angles to the nearest contour lines (which are almost certainly not parallel, so it may be very approximate), through your house or apartment block. Along this rough line, as the contour numbers go up, you’re headed uphill, and as they go down, you’re headed downhill. This may not be apparent in the visual landscape, and it certainly may not be apparent in your own impression of walking there. Unless hills are quite steep, we tend to assume that the spaces we pass through are flat. Alternately, assuming you’re not one yourself, ask a wheelchair user; they will know much better where all the hills are.

Extend the uphill line until the contour numbers start to go down again (that is, your line has reached the top of a rise and started to go down the other side). Does your line cross a waterway or body of water? If so, your home is downhill from it, and may be at risk of floods during periods of heavy rain. You’ll probably need to go and look at it before you can be sure, though.

Now extend the downhill line. Does it cross a waterway before it crosses a contour line? If so, you’re not very far uphill (even though you might be a long way in horizontal distance) from that waterway, and flooding there might reach you. Again, you’ll need to go look to know more.

It’s worth looking a little way to either side of your uphill and downhill lines, too - as much as 45 degrees to either side. It’s entirely possible for a curving waterway to come close to the lines, but not intersect them, and you might well be downhill or not-very-uphill from those too. Once you’ve located any such places on your map, it’s time to go on to the next step.

Exploration & Observation

If you’ve located places where your uphill and downhill lines intersect waterways, or come near to them, then those are first places you want to go and look at. If not, you want to go and look at the nearest waterways or bodies of water, no matter where they are. It is possible, I think, in some American cities (Las Vegas, looking at you) to be so far from a body of water that it’s just not conceivable that water from it could reach you, and it’s possible anywhere that you’re on a steep enough hill with no water uphill that again, only floods of biblical proportions could reach you. In European towns and cities, this is is less likely. It’s also less likely if you’re in a newer building; older buildings tend to be on higher, more flood-safe ground. A new building in a rural area is honestly anyone’s guess.

You want to visit those intersection points and nearby waterways at least twice, once in relatively dry weather, and once after heavy rainfall (or even during it, although exercise care). Look at the water levels, and take pictures on both visits. When you compare the pictures, you can see how much higher the water is after heavy rain, and you can make a guess as to how much rain it would cause for that waterway to overflow. Artificial waterways tend not to overflow sideways, as it were, but to rush out of the ends of their courses; canals usually eventually give into the sea or a basin of some kind, so there’s less risk of those overflowing. You will see areas where there are sluice gates, though, which can be opened to take the pressure off areas further down the flow. These often give onto grazing fields, wetlands, parks or playing fields; places where lying water will do no short-term harm.

Aside from “how much rain will cause flooding”, you also want to look at the land between the waterway and where you live. If it has lots of trees and green spaces, that’s good; those absorb water much better than concrete or tarmac can. If it’s mostly paved over, that’s not so great. If it’s paved over with a road that leads directly downhill to where you live, with walls and other barriers on both sides of the road, well, you can see how that goes. Similarly, if there’s nothing but a car park or low-lying fields between you and a waterway, then it doesn’t take a lot of extra water to turn that into a shallow lake.

Also, walk a circle around your home - not the building itself, although that’s no harm - but the closest “round the block” walk you can do, and look at the shape of the land, and the other details of outlets and drainage, access routes, and so on, as below, and then do the the same thing one “block” further out, as much as you can. In rural areas, this might involve walking through some fields rather than roads.

Outlets & Drainage

Look for outlets and drainage between you and the waterway as well. Old ditches dug alongside hedgerows are the actual ideal; those will be well-established, tested, and adjusted to carry away as much water as possible, often over centuries (in Europe, at least). If there are three or more of those between you and the waterway - and they don’t all connect in to the same place immediately - you can probably relax a fair bit.

Anything that carries water away from the area is an immediate benefit. Of course, the most effective way for this to happen is a huge open concrete culvert running across your uphill line - but that dumps all the water down a different hill and causes someone else hassle instead, so it’s not a good thing in the longer term. Not to mention that when those things are overwhelmed (which can happen if people further upstream shunt all their excess water down to you), they overflow spectacularly and with a lot of damage. In assessing your immediate risk, though, take account of anything like this that exists.

Grates and other small access points to underground drains - which occur in nearly every street and car park - are good for lower volumes of water, but they can easily be overwhelmed or blocked. You might get an idea of their capacity by seeing how they’re doing during or immediately after heavy rain. Once they’re blocked, they turn the street they’re in into a stream, channeling water further downhill, or if they’re in a local low point (as in a car park or the end of a cul-de-sac), they can turn into a small local flood, a pool that grows until it finds some other overflow point.

Tides

If you’re near the sea, or in the tidal range on a river, you’re also going to have to take account of that. Tides affect the Liffey up as far as Strawberry Beds (about 13km from the sea) and the Slaney as far as Enniscorthy (about 23km from the sea), so this can happen quite a long way inland. The Barrow is tidal to St. Mullins in Carlow - a landlocked county - and that’s about 33km. Ideally, visit the river or a harbour or the like during a spring tide, and see how high the water is then. A storm surge could add as much as a metre to this, and since storms are often accompanied by heavy rain, a high tide coinciding with a storm can push water an unbelievable distance up and inland.

You can usually find out where the tidal limit is on a river via Google; the phrase “normal tidal limit” will be of some use. Some of these limits will change over the next few years and decades as sea levels rise, mind. Many of them are at weirs or small waterfalls or the like, so that when eventually those are overtopped by tides, the next tidal limit may be quite a bit further inland.

Access Routes

Apart from the building where you live, take account as well of how you get to and from it. Many housing estates and aprtment complexes in Ireland have only one entrance by which cars can come and go, and there are plenty of places where one bridge being flooded or otherwise impassable can result in a journey of many miles via the next bridge to a place that’s literally in shouting distance over the water. If there are low points in your access routes, take note of those as well. It’s occasionally possible to have access on foot but not by car - footpaths between estates are not uncommon, and footbridges over rivers, canals and the like are often higher than the road bridges near them.

Assess where you’d need to park a car where it could get out if there’s a floodable point between your house and work, school, or shops that you can get around on foot. This is also the nearest point at which you can someone drop stuff off for you if you’re flooded in.

Local Knowledge

Finally, ask your neighbours about flooding. Older people in particular, because in many cases they’ll have been in the same house for a few decades, and have a better idea of what the local conditions are like. Someone who works outdoors - farmers, allotment owners, people who work at stables or as groundskeepers, and most particularly postal delivery people - will be able to tell you more as well. There are all kinds of odd effects of slight rises, concreted areas, underground car parks, skate parks, and so on which can make very unexpected differences in which places flood, and how. Local knowledge trumps anything I can tell you!

Finally, for an example of flood handling that’s just shown up, this guy who lives by the River Severn in the UK built his own flood wall, and it looks like it works perfectly. I would, I think, be building it a bit higher myself, but it absolutely works.

Closing

I hope this has been useful. I do think that exploring your local area can be very rewarding even if you’re not assessing flood or other climate risks - I’ve found four or five places I can pick apples in Maynooth by wandering around with the dog, and there’s a very fine climbing rose that I intend to take a cutting from when I get a chance.

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