Alex Lipp
@alexlipp.github.io
Lecturer in Earth Sciences @es-ucl.bsky.social | Interested in rivers, mud, mountains, pollution, carbon cycling, quantitative methods, open science | alexlipp.github.io | www.sewagemap.co.uk | he/him | 🌍 🌱 🏔 🧗♂️ 🏕 🏃♂️
This was a very fun project to work on, with some neat stats & maths from fractals to fluid mechanics. We were surprised that for such a high profile dataset like sewage spills there had been such limited public statistical analysis until now! 💩 🧮 🧑💻
eartharxiv.org/repository/v... 8/8
eartharxiv.org/repository/v... 8/8
December 11, 2025 at 7:52 AM
This was a very fun project to work on, with some neat stats & maths from fractals to fluid mechanics. We were surprised that for such a high profile dataset like sewage spills there had been such limited public statistical analysis until now! 💩 🧮 🧑💻
eartharxiv.org/repository/v... 8/8
eartharxiv.org/repository/v... 8/8
What causes the heavy tail? When trying to replicate it using hydraulic models we can only do so by including infiltration of groundwater into pipes through cracks… this suggests that these long duration spills are *not* only occurring after heavy rain…
eartharxiv.org/repository/v...
6/
eartharxiv.org/repository/v...
6/
December 11, 2025 at 7:52 AM
What causes the heavy tail? When trying to replicate it using hydraulic models we can only do so by including infiltration of groundwater into pipes through cracks… this suggests that these long duration spills are *not* only occurring after heavy rain…
eartharxiv.org/repository/v...
6/
eartharxiv.org/repository/v...
6/
We think this is driven by daily fluctuations in water usage (🚿 💩) which modulates the length of sewage spills…
eartharxiv.org/repository/v...
5/
eartharxiv.org/repository/v...
5/
December 11, 2025 at 7:52 AM
We think this is driven by daily fluctuations in water usage (🚿 💩) which modulates the length of sewage spills…
eartharxiv.org/repository/v...
5/
eartharxiv.org/repository/v...
5/
A total (and cool 🤓) surprise for us, was the discovery of a periodic variation of the misfit to this modelled trend, fluctuating around spills that are multiples of 24 hours long… what’s causing this?
eartharxiv.org/repository/v...
4/
eartharxiv.org/repository/v...
4/
December 11, 2025 at 7:52 AM
A total (and cool 🤓) surprise for us, was the discovery of a periodic variation of the misfit to this modelled trend, fluctuating around spills that are multiples of 24 hours long… what’s causing this?
eartharxiv.org/repository/v...
4/
eartharxiv.org/repository/v...
4/
Statistically, this tail is well described by a stretched exponential distribution. It’s not quite as heavy as a power law, but much heavier than a vanilla exponential…
eartharxiv.org/repository/v...
3/
eartharxiv.org/repository/v...
3/
December 11, 2025 at 7:52 AM
Statistically, this tail is well described by a stretched exponential distribution. It’s not quite as heavy as a power law, but much heavier than a vanilla exponential…
eartharxiv.org/repository/v...
3/
eartharxiv.org/repository/v...
3/
We find that sewage spills follow a very heavy-tailed distribution. 10% of spills account for 85% of all spilling *time*. So, it’s not the infrequent, short spills we should care about, it’s the infrequent long ones…
eartharxiv.org/repository/v...
2/
eartharxiv.org/repository/v...
2/
December 11, 2025 at 7:52 AM
We find that sewage spills follow a very heavy-tailed distribution. 10% of spills account for 85% of all spilling *time*. So, it’s not the infrequent, short spills we should care about, it’s the infrequent long ones…
eartharxiv.org/repository/v...
2/
eartharxiv.org/repository/v...
2/
In our 💫 new preprint 💫 Barney Dobson & I drill into the statistics behind “shitty” headlines like these about the number & duration of sewage pollution spills.
We analyse a dataset of nearly 4 million individual #sewage spill events… 1/
eartharxiv.org/repository/v...
We analyse a dataset of nearly 4 million individual #sewage spill events… 1/
eartharxiv.org/repository/v...
December 11, 2025 at 7:52 AM
In our 💫 new preprint 💫 Barney Dobson & I drill into the statistics behind “shitty” headlines like these about the number & duration of sewage pollution spills.
We analyse a dataset of nearly 4 million individual #sewage spill events… 1/
eartharxiv.org/repository/v...
We analyse a dataset of nearly 4 million individual #sewage spill events… 1/
eartharxiv.org/repository/v...
OTOH the environment agency *is* massively under-resourced so not totally their fault, *but* this defence is totally inappropriate… You’re an arm of the State, it’s right and good to be subject to criticism and you need to respond to it better than “uwu don’t be so mean” 🙄
November 15, 2025 at 4:45 PM
OTOH the environment agency *is* massively under-resourced so not totally their fault, *but* this defence is totally inappropriate… You’re an arm of the State, it’s right and good to be subject to criticism and you need to respond to it better than “uwu don’t be so mean” 🙄
so pleased everyone is choosing such unique and distinctive typefaces
October 16, 2025 at 11:27 AM
so pleased everyone is choosing such unique and distinctive typefaces
The perfect conditions continue 😎 🌞!
September 6, 2025 at 8:50 AM
The perfect conditions continue 😎 🌞!
… and blessed with some Aurora Borealis too! #studygeologyandseethenorthernlights
September 5, 2025 at 5:11 PM
… and blessed with some Aurora Borealis too! #studygeologyandseethenorthernlights
Stunning conditions (and enthusiastic students!) for the first few days of the @es-ucl.bsky.social mapping course in North West Scotland! ☀️ ⛰️ ⚒️🏴 🗺️ #fieldworkfriday
September 5, 2025 at 5:11 PM
Stunning conditions (and enthusiastic students!) for the first few days of the @es-ucl.bsky.social mapping course in North West Scotland! ☀️ ⛰️ ⚒️🏴 🗺️ #fieldworkfriday
Me to students: "Keep field notebooks legible, and only write down the most relevant information".
My own notebooks:
My own notebooks:
August 11, 2025 at 2:02 PM
Me to students: "Keep field notebooks legible, and only write down the most relevant information".
My own notebooks:
My own notebooks:
Shocked to hear that Stream, which has given Esri huge sums of bill payer money to create an extremely basic API, has won an award from…. Esri! Trebles all round…
August 5, 2025 at 8:24 AM
Shocked to hear that Stream, which has given Esri huge sums of bill payer money to create an extremely basic API, has won an award from…. Esri! Trebles all round…
eartharxiv.org/repository/v...
In our new preprint we describe in detail the software & workflows behind www.SewageMap.co.uk! One for the open environmental data nerds out there :) 💩 🧑💻 🏞️
In our new preprint we describe in detail the software & workflows behind www.SewageMap.co.uk! One for the open environmental data nerds out there :) 💩 🧑💻 🏞️
July 31, 2025 at 6:41 AM
eartharxiv.org/repository/v...
In our new preprint we describe in detail the software & workflows behind www.SewageMap.co.uk! One for the open environmental data nerds out there :) 💩 🧑💻 🏞️
In our new preprint we describe in detail the software & workflows behind www.SewageMap.co.uk! One for the open environmental data nerds out there :) 💩 🧑💻 🏞️
Putting together a NERC proposal and somewhat baffled by what NERC mean when they want a Summary to be suitable for "opinion-formers". Who are these people and how am I meant to write for them?!
June 4, 2025 at 11:17 AM
Putting together a NERC proposal and somewhat baffled by what NERC mean when they want a Summary to be suitable for "opinion-formers". Who are these people and how am I meant to write for them?!
I don’t think this is true at all. Crushing rocks makes up 1% of all energy usage globally and is proportionally one of the biggest energy outlay of the entire mining sector (source: www.ceecthefuture.org/resources/mi...)
May 28, 2025 at 9:16 PM
I don’t think this is true at all. Crushing rocks makes up 1% of all energy usage globally and is proportionally one of the biggest energy outlay of the entire mining sector (source: www.ceecthefuture.org/resources/mi...)
Really excellent news, and should never have been doubt. The original protest on Dartmoor was a hugely moving event and has sparked a new wave of R2R movement ⛰️ 🏕️ 🌱
May 21, 2025 at 8:37 PM
Really excellent news, and should never have been doubt. The original protest on Dartmoor was a hugely moving event and has sparked a new wave of R2R movement ⛰️ 🏕️ 🌱
Stop-Start data (i.e., *when* spills happened) is much more informative as it identifies potential links to rainfall, capacity etc... but only Thames Water actually readily share this data (see screenshot from sewagemap.co.uk). So, water co's don't help themselves! More open-data please!!!
March 27, 2025 at 11:09 AM
Stop-Start data (i.e., *when* spills happened) is much more informative as it identifies potential links to rainfall, capacity etc... but only Thames Water actually readily share this data (see screenshot from sewagemap.co.uk). So, water co's don't help themselves! More open-data please!!!
www.theguardian.com/environment/...
The new government policy on bathing water status seems to be taking direct inspiration from the survivorship bias meme, for some reason?!?
The new government policy on bathing water status seems to be taking direct inspiration from the survivorship bias meme, for some reason?!?
March 12, 2025 at 9:39 AM
www.theguardian.com/environment/...
The new government policy on bathing water status seems to be taking direct inspiration from the survivorship bias meme, for some reason?!?
The new government policy on bathing water status seems to be taking direct inspiration from the survivorship bias meme, for some reason?!?
Question for #hydrology #dataviz and #webdev folks… has anyone seen a visualisation like the below from earth.nullschool.net (by @cambecc.bsky.social)
but for river discharge not wind speed?? Sure I saw something similar previously but now can’t remember where!
but for river discharge not wind speed?? Sure I saw something similar previously but now can’t remember where!
February 10, 2025 at 7:53 PM
Question for #hydrology #dataviz and #webdev folks… has anyone seen a visualisation like the below from earth.nullschool.net (by @cambecc.bsky.social)
but for river discharge not wind speed?? Sure I saw something similar previously but now can’t remember where!
but for river discharge not wind speed?? Sure I saw something similar previously but now can’t remember where!
…but as ever @jonnydawe.github.io and I have been stymied by most water companies limiting the data they release!
January 26, 2025 at 6:08 PM
…but as ever @jonnydawe.github.io and I have been stymied by most water companies limiting the data they release!
www.sewagemap.co.uk now has national coverage! North Devon getting a bit of a pasting right now 💩 💩…
January 26, 2025 at 6:08 PM
www.sewagemap.co.uk now has national coverage! North Devon getting a bit of a pasting right now 💩 💩…