We have come across an illustrating source of a network of security cameras capturing a flash flood in Ellicott City, Maryland, US on Sunday 27th of May 2018. The video is a collage of 12 cameras all located on or near the Main Street in Ellicott City. The information from these videos would have been useful at the time of the flooding.
The videos clearly show how the Patapsco River and two out of its four tributaries (Tiber River and Hudson River) rapidly swell and overflow. We see how this results in the Main Street also becoming a fast flowing river with water washing away cars, destroying buildings, and accumulating debris. The flood lasted only four hours but caused catastrophic damage to local infrastructure, residents property, and claimed a life of a National Guardsman [1,4].
The cameras were installed by a local property owner, Ron Peters and can be seen in this YouTube video:
The flooding event
A storm released nearly two months of rain, over 9 inches (24cm) in just two hours (3 to 5pm local time), which swept away several roads, cars and brought more than 10 feet (3.0 m) of rapidly moving water down Main Street in the Old Ellicott City . The old city is a very urban area set in a valley next to Patapsco River and its four tributaries. Due to the urban landscape the rainfall has nowhere to go except for running down the valley to the main river.
This was the second 1-in-1000 flood event within two years in Ellicott City. Both 2016 and 2018 events claimed lives and caused millions of dollars in damage [1,4]. However, flooding is nothing new to this city. The city officials are looking into introducing green areas in the city to allow the rain water to be absorbed into the ground reducing the surface runoff.
New flood alert system
Associate Professor Nirmalya Roy and his group from University of Maryland Baltimore County (UMBC) are working on using a network of temperature and liquid sensors and have produced a new flood warning system for Ellicott City [2,4]. They are also working on using the local flood related information from social media such as Twitter into the flood alter algorithm which warns public through loudspeakers in the city [3,4].
It is clear that the videos captured from these security cameras provide a rich source of water information of the rivers and the Main Street. Information such as water levels and surface velocities can be extracted from these videos  and used as part of an existing flood warning system or an independent one. Further, videos also capture additional information on floods and damage caused that is valuable to rescue teams, insurance companies etc.
The Dare team went on a field trip last month! It was a well planned and executed trip – as you would expect from a group of mathematicians. It was also a very interesting trip for us since most of us have only ever used data (e.g. for improving forecasts) not collected it. Even better Tewkesbury area has become a sort of benchmark for testing new data assimilation methods, ideas, tools, observations, etc, and so many of us have worked with LisFlood numerical model (developed by a team led by Prof. Paul Bates at the University of Bristol) over the Tewkesbury domain. We have seen the river runs in the model outputs, watched the rivers Avon and Severn go out of banks in our plots, and investigated various SAR images of the area but we have never been to the area. We generally do not need to visit the area when working with the models, however, now that there was a chance to do so, it was no surprise that many of us were keen to go. And we did go like ‘d’ A-team:
However we had a more important reason for visiting too – we were going to the Tewkesbury area to collect metadata from a number of river cameras located near Tewkesbury town. These river cameras are high definition webcams owned and serviced by Farson Digital Ltd in various location over the UK. We had recently discovered that six of such cameras are within the LisFlood model domain and have captured the November 2012 floods in the area. With the permission from the Farson Digital Ltd, we have obtained hourly daylight images of the floods from 21st November 2012 to 5th of December 2012. Hence, the aim our trip was to obtain accurate (with errors of no more than few centimeters) positional information (i.e. latitude, longitude, height) of the cameras themselves as well as the positional information of a number of markers in the images for each of the cameras. We need this information to extract as accurately as possible water extents and water depth from these images using image processing tools (which we are currently working on).
To take these measurements we had borrowed some tools from the Department of Geography at the University of Reading. We used a differential GPS tool (GNSS) to very accurately (on order of few centimeters) measured the position of a given point in 3D space, that is its latitude, longitude, and height above the sea level, however, it had to be used on the ground (e.g. could not measure remote or high points such as building corners where some cameras were mounted) and not be too close to buildings or large trees. To measure remote and high points we used Total Station, which allowed us to shoot a laser beam to the desired point to measure its 3D position in space.
We had planned to visit all six cameras within the space of the two days 16th and17th of April, however, despite our best plans and fantastic organisation skills we were too ambitious with our time and we had to drop the camera furthest from our base – the Bewdley camera (see map with camera positions in figure 2). Thus, on our first day, we took measurements from Wyre Piddle, Evesham, and Digglis Lock cameras, spotting ourselves live on the Farson Digital Ltd site.
We returned to our base – the Tewkesbury Park Hotel, to be joined by the Ensemble team from the Lancaster University. Ensemble Project is lead by Prof. Gordon Blair, and as Dare is funded by the EPSRC Senior Fellowship in Digital Technology for Living with Environmental Change. It was very interesting to meet the Ensemble project team and learn more in-depth about their work, future interests, and scope for the collaboration.
On our second day, the Dare team visited the Tewkesbury camera while the Ensemble team learned more about the purpouse of the data collection and the Novermber 2012 floods in the area. Then we all jointly measured a large number of points at the Strensham Lock. In 2012 we all would have been totally sumberged in water in this picture since the flood waters completely swallowed the island on which the house is standing flooding the building along with it.
Our grand finale was the meeting with the director of the Farson Digital Ltd Glyn Howells as well as a number of stakeholders who have commissioned the cameras we visited. It was very interesting for us to learn how the network of the river cameras was born from the need to know and understand the current state of the river for a variety of river users – fishermen, campers, boaters, etc. Also, how these cameras have become invaluable assets to many stakeholders for various reasons – greatly reducing the number of river condition related phone enquiries, monitoring river bank and bridge conditions, and so on.
Now a month later we have downloaded and processed the data we collected from these stations. In figure 7 we have plotted the data points we took at the Tewkesbury site, owned both by the Environmental Agency and Tewkesbury Marina (both of which we greatly thank for their support and assistance before and during our trip, especially to Steve Edgar from EA and Simon Amos and Bruno from Tewkesbury Marina). In the figure, the red dots are the camera positions – pre-2016 and current camera positions, and the black dots are all the other measurements we took using both the TotalStation and GNSS tools, which are plotted against the Environmental Agency lidar data with 1m horizontal resolution.
We are currently working on extracting the water extent from these images which we then will use to produce water depth observations. Our final aim is to see how much forecast improvement such rich source of observations offer, in particular, before the rising limb of the flood.
We are very thankful to Glyn Howells and the various stakeholders for permitting us to use of the images, allowing us to take the necessary measurements, assisting us on the sites, and joining at the workshop!
It is difficult to accurately predict urban floods; there are many sources of error in urban flood forecast due to unknown model physics, computational limits, input data accuracy etc. However, many sources of model and input errors can be reduced through the use of data assimilation methods – mathematical techniques that combine model predictions with observations to produce more accurate forecast.
In this talk I will motivate and introduce the idea of using CCTV images as a new and valuable additional source of information in cities for improving the urban flood predictions through data assimilation methods. This work is part of the Data Assimilation for REsilient City (DARE) project.
You can see the whole presentation on YouTube here or view slides here.
On Friday 2nd of June 2017 Met Office issued a yellow warning of heavy rain with possible hail and lightning over London. Also Environmental Agency issued a number of flood alerts for London for the same period of time. This allowed us to test our newly setup system for recording open data CCTV images from London Transport Cameras (aka JamCams).
Following the flood alerts we setup to record all Transport for London (TFL) cameras which where within the main flood alert areas, these were 4 areas in London.
This resulted in downloading images from just over 110 CCTV cameras accross from the marked areas in Figure 1. Dowload started on many cameras at 2:30pm on 2nd of June 2017 and continued for 24h with an image downloaded every 5min.
Many of these images showed heavy rain as it passed over London on the afternoon of the 2nd June 2017; some cameras even captured images of lightning which was seen over North London but we didn’t capture any images of flooding in the four coloured areas in Figure 1.
However, following the flooding allert on London for Transport site allowed us to capture surface flooding that happened on the North Circular road between 4-7pm resulting in traffic jams in the area.
The surface flooding was very localised and only one camera captured it, the one just below the blue circle in the Figure 4. We recorded both still and video images from this camera.
We are currently setting up similar systems to download live traffic CCTV images from Leeds, Bristol, Exeter, Newcastle, Glasgow, and Tewkesbury.
by Sanita Vetra-Carvalho Urban areas nowadays contain many observation networks such as CCTV cameras looking at buildings, streets, parking lots, rivers and traffic. Also, where there are people there are smartphone images, which are another potential source of information that can be assimilated in urban flooding models to get more accurate flooding forecasts. Increasing number of research teams and organisations are using this abundance of data and while much CCTV data is available as open data, smartphone images need to be collected from the community. Below we list the networks of CCTV data and crowdsourcing sites known to us for the areas we are interested in: London and the Thames Valley, Exeter, Newcastle, Leeds, Glasgow, and Tewkesbury. This list is not complete and if you know of further sites or webcams we would love to hear from you (email to: email@example.com)!