It is fitting that an Atlantic hurricane which shares its name with our director of hydrology should be noted for its particular hydrological impact. The most serious impact from Hurricane Harvey has been the extreme rainfall which has now amounted to over 1000mm in the four days from 25-28th August. By contrast the average annual total at our office location in Oxfordshire, UK, is 611mm. The rainfall associated with Hurricane Harvey has been described as unprecedented although tropical cyclones have produced similar amounts of rainfall in other parts of the world. For example, Hurricane Mitch brought moist air from the Pacific over Central America in October 1998 and 928mm was recorded over 5 days with unofficial estimates of 1,900mm. Typhoon Nina which hit China in August 1975 reportedly brought over 1000mm of rainfall in 24 hours and led to the failure of 62 dams. This PDF has more detail on the impact of the flooding including a map showing potential flood extents. Hurricane Harvey
Due to some urgent field work at short notice Dr Harvey Rodda was unable to give his presentation at the ESRI UK user conference on 18th May 2017. Here is a document summarising the study. East Hanney Presentation
Hydro-GIS Ltd is proud to contribute to the Wallingford Corn Exchange Roof Fund Appeal. The Corn Exchange is a local theatre run by volunteers in Wallingford. It has previously been supported by DEFRA and EU funding. As we are currently placed in the grim situation where one of those funding sources will no longer be available it is all the more important to help contribute to these local projects.
Dr Harvey Rodda is supervising a UCL MSc dissertation as part of the geophysical hazards course on the topic of the 1606 Bristol Channel Tsunami, and also supervising a NHFI project on the comparison of the 2005, 2009 and 2015 Cumbria floods. Laura Vecera is currently undertaking her MSc dissertation at Freiburg University on karst groundwater in China, which includes 3 weeks of fieldwork in China.
Since March Hydro-GIS Ltd has a hybrid company car, a BMW 225xe. This will enhance our green transport policy and will be able to ensure zero emission mileage for local journeys. We are very pleased to have a hybrid vehicle from a quality European manufacturer and have achieved low fuel consumption figures of 2.6 l/100km (106 miles per gallon), with 60% of our total distance travelled being through electric power with zero emissions.
Hydro-GIS Ltd has been working as part of a team of experts to look at the risk of tailing dam failure in Chile. Our input has included to application of a dam breach model to identify the potential risk to downstream areas and using rainfall runoff modelling to identify the risk of dam failure caused by overtopping.
Hydro-GIS Ltd worked together with researchers from the Open University in a pilot study to test using a drone for mapping flood extents.
The approach has a number of potential applications such as demonstrating flood extents in areas where EA flood maps are inaccurate, which is particularly common for small streams, and to assist insurance companies in estimating losses and dealing with bogus claims. The study however found a number of limitations including the logistics of mobilising the drone to capture the full flood extent, legal restrictions on the routes which can be flown, problems with drone battery life, and problems with software used to process images and generate the high resolution digital terrain models.
On the positive side however we have maintained our link with the Open University and have access to use the drone for further detailed mapping studies. Please contact Dr Harvey Rodda for more details here.
The full report can be accessed here.
Through his role at UCL Dr Harvey Rodda has been supervising four MSc dissertations on storm surges along the English Channel coast, the risk of dam breach flooding in the PeaK District National Park, flash flood risk in Chile, and the relationship between drought periods in Southern Spain and the North Atlantic Oscillation.
The recent implementation of Flood Re to guarantee flood cover for households in the UK has led to an increased interest in the flood risk to insurance company portfolios. Hydro-GIS Ltd were engaged by Axa Art to undertake hydrological field surveys to provide a detailed assessment of the flood risk at six sites which had been flagged up as having the highest risk of the whole portfolio when using a desk-based classification with standard “off the shelf flood” risk mapping products.
The surveys identified that only one of the sites remained at high risk and three were considered a moderate risk given they had experienced some flooding in the past but had since included flood alleviation measures. Of the two remaining sites identified by the surveys as low risk, one was located halfway up a hillside some 50m in altitude above the small stream to which the flood risk at the site would be attributed.
This highlights the potential degree of inaccuracy from the desk based risk mapping products and the benefit of field surveys to give a fuller assessment of flood risk.
Dr Harvey Rodda has recently co-authored a hydrology textbook with Dr Max Little from the Department of Engineering and Applied Science, Aston University. The aim is to provide assistance to hydrology students and practitioners with some of the more complicated mathematical aspects of the subject. The book is available as an e-book as well as in print.