South Yorkshire: A HISTORY OF FLASH FLOODING Introduction There is no agreed definition of a flash flood. For the purposes of this chronology and in line with the requirements of the SINATRA project to investigate ‘flooding from intense rainfall’, the following definition (Archer and Fowler 2016) is used: A flood resulting from intense short duration rainfall, usually convective, that exceeds drainage capacity in urban areas or infiltration capacity in rural areas and hence can flood land and property far from rivers. River response is rapid with possible near vertical wave fronts in river channels; river users and floodplain residents may be endangered by rapid rates of rise in river level which may be enhanced by failure of upstream structures or antecedent saturation of the catchment. Flash floods may cause serious erosion of hillsides and river channels and may carry heavy loads of floating debris and boulders which may be deposited in berms and terraces. The past focus on the history of flooding has been mainly with respect to flooding from the overflow of rivers and with respect to the peak level that these floods have achieved. The Chronology of British Hydrological Events provides a reasonably comprehensive record of such events throughout Great Britain. Over the last 60 years the river gauging network provides a detailed record of the occurrence of river flows and peak levels and flows are summarised in HiflowsUK. However there has been recent recognition that much flooding of property occurs from surface water flooding, often far from rivers. Locally intense rainfall causes severe flooding of property and land as water concentrates and finds pathways along roads and depressions in the landscape. In addition, intense rainfall can also cause rapid rise in level and discharge in rivers causing a danger to the public even though the associated peak level is not critical. In extreme cases rapid rise in river level may be manifested as a ‘wall of water’ with near instantaneous rise in level of a metre or more. Such events are usually convective and may be accompanied by destructive hail or cause severe erosion of hillsides and agricultural land. However, since the boundary between a flash flood and a ‘normal’ flood has not yet been clearly defined, some events are included in the following chronology which may not qualify as ‘flash floods’ but are retained to help establish a future boundary between flash and ‘normal’ events. There have been no previous compilations of historical records of such ‘flash floods’or even of more recent occurrences. It is therefore difficult to judge whether a recent event is unusual or even unique in terms of the level reached at a particular location or more broadly of regional severity. This chronology of flash floods is provided in order to enable comparisons to be made between recent and historical floods, to judge rarity and from a practical point of view to assess the adequacy of urban drainage networks (Archer et al 2017). In the following chronology for South Yorkshire events are listed by date and by the source of the information. Where meteorological information is available especially rainfall depths over daily or shorter durations, this is listed in the second column. The description of the event then indicates the location and extent of the flooding, including levels or depths on roads and buildings which may still be identifiable. The occurrence of associated hail and especially of large hail has been included where available. Information of human interest but lacks indication of the magnitude of the flood has generally been omitted. The earliest record for South Yorkshire is from 1594 and information is intermittent or description is sparse until 1800 after which the listing of occurrences is considered comprehensive and by 1850 multiple sources provide detailed accounts. This chronology is part of a set of regional compilations of flash floods for Northern England and for Southwest England and includes the following separate chronologies. Yorkshire Rye and North York Moors Yorkshire Swale Northeast England River Eden Derwent and Cumbrian Coast South Cumbria Kent and Leven etc Lancashire Including neighbouring counties draining to the Mersey estuary Southwest England – Cornwall and Devon In addition, a more selective compilation of extreme events has been created for the remainder of the British Isles. This is not intended to be comprehensive but picks out events which have been noted by the compiler. Meteorological information As a first step in identifying potential dates of flash flooding the publication British Rainfall 1863 – 1968 (Symons British Rainfall from 1863 to 1900) was inspected to ascertain the meteorological conditions associated with flooding – thaw, thaw with rain, frontal rainfall, convectional storms etc. Of particular interest were the records provided of rainfall amounts of specified short duration. Early records of short period intensity were usually derived by observation of the amount and start and end time of intense rainfall. Later records were extracted from recording rainfall gauges, either Dines Siphon or Tilting Bucket records. Very high daily totals were also noted. Those relevant to south Yorkshire were extracted. The Climatological Observers Link (COL) from 1970 to the present has been used to fill out the later period for intense rainfall although the number of stations is small especially in the early years during the 1970s but is supplemented by observer’s descriptions of events. Philip Eden’s Great British Weather Disasters provides a chronology of severe events from 1901 to 2008, including strom winds, snow and thaw, and intense or prolonged rainfall. Sources of flood Information Descriptive information is contained in newspaper reports, diaries and further back in time, from Quarter Sessions bridge accounts and ecclesiastical records. The main source for this study has been from newspaper accounts. Early Newspaper Source The Lexis British Newspaper Archive has digitised large continuous runs of newspapers which have been accessed on the web. A search facility identifies all occurrences of given words or combinations of words, by newspaper, by county, by region and by date. The phrase ‘flash flood’ is a 20th century description, so alternative words were required to ensure that all potential flash flood events were identified, without producing an excessive number of irrelevant events. The words ‘flood’ and thunder’ were adopted. The search facility includes within these words variants such as ‘flooding’ and ‘thundering’. Up to 50% of the occurrences identified were of descriptions of ‘floods of tears’ or ‘thundering speeches by politicians’ but is likely to have produced a comprehensive set of flash flood events. All relevant information was extracted from the identified descriptions, such as location, associated meteorological conditions, the occurrence of hail, magnitude and extent of flooding, depth in buildings, fatalities from drowning or lightning, animal losses, bridges and buildings damaged by flood or lightning, severe channel erosion and descriptions of rapid rate of rise in level. Except where events were of very unusual magnitude, winter floods produced by long duration rainfall or snowmelt events were excluded. Only information which could be used to define the magnitude or severity of a historical flood in relation to a recent gauged flood has been included. The following is a list of the newspapers that have been accessed on the British Newspaper Archive, with the dates currently available. It is noted that although some papers continue publication to the present, for copyright reasons the current archive extends only to 1900 or to 1950. Hence records are most comprehensive for the period from 1850 to 1900, but sufficient newspapers are archived up to 1950 to provide comprehensive data up to that date except for the years of World War II when press restrictions were placed on natural incidents such as thunderstorms and floods. Newspaper Place of Publication Available dates Barnsley Chronicle Barnsley 1858-1910 Beverley and East Riding Recorder Beferley 1855-1916 Beverley Echo Beverley 1885-1903 Beverley Guardian Beverley 1856-1877 Bradford Daily Telegraph Bradford 1868-1909 Bradford Observer Bradford 1834-1880 Driffield Times Driffield 1869-1949 Dewsbury Reporter Dewsbury 1869-1884 Halifax Courier Halifax 1853-1939 Huddersfield and Holmfirth Examiner Huddersfield 1851-1856 Huddersfield Chronicle Huddersfield 1850-1900 Huddersfield Daily Examiner Huddersfield 1914-1918 Leeds Intelligencer Leeds 1754-1866 Leeds Mercury Leeds 1807-1939 Leeds Patriot and Yorkshire Advertiser Leeds 1826-1833 Leeds Times Leeds 1833-1901 Northern Star and Leeds General Advertiser Leeds 1838-1852 Pontefract Advertiser Pontefract 1858-1891 Shipley Times and Express Shipley 1882-1957 Wetherby News, and Central Yorkshire Journal Wetherby 1877-1879 Yorkshire Post and Leeds Intelligencer Leeds 1866-1955 Hull Advertiser and Exchange Gazette Hull 1794-1867 Hull and Eastern Counties Herald Hull 1864-1871 Hull Daily Mail Hull 1895-1950 Hull Packet Hull 1800-1886 Sheffield Daily Telegraph Sheffield 1855-1950 Sheffield Evening Telegraph Sheffield 1887-1939 Sheffield Independent Sheffield 1819-1938 Tadcaster Post Tadcaster 1861-1879 Whitby Gazette Whiteby 1854-1918 Whitby Times, and North Yorkshire Advertiser Whitby 1873-1877 York Herald York 1801-1900 Yorkshire Evening Post York 1890-1954 Yorkshire Evening Press York 1885-1898 Yorkshire Gazette York 1819-1899