WRA Bulletin 51 January 2019 OVERSEAS WORK bridges, while smaller crossings have multi-barrel culverts. Models were configured using high-resolution Somaliland wadi crossings satellite imagery to produce a 1m-DTM and valley and WRA continues to work widely in Somaliland and has channel cross-sections. supported CONSER in the design and reinstatement of wadi crossings [toggas] along the 250 km highway from the port of Berbera to the Ethiopian border town of Wajale, which passes through the capital city of Hargeisa. Model of Maroodi Jeex 100-year flood at Awbarkhadle Tug Henweina downstream of the LaFarug crossing UK WORK Fairford groundwater levels The work has involved hydrological and hydraulic modelling of 15 of the largest toggas by a team lead by Fairford, in Gloucestershire, historically suffered many Partner Paul Holmes, including Associates David flooding incidents from the River Coln which were also Plinston, Julian Smith and Peter Baur. exacerbated by groundwater and surface water. A river flood alleviation scheme was introduced by the There are three large catchments over 300 km2 in area, Environment Agency in 2013. and three small catchments of less than 10 km2, three toggas draining the plateau farming area west of Hargeisa, and the remainder are moderate size toggas associated with drainage of the Assa Range of hills and Auradu escarpment between Awbarkhadle and Mandera. TRMM-GPM rainfall data were used to supplement ground data, and an analysis was made of the recent cyclone Sagar. YEMEN Socotra Drilling borehole A2 in the snow at Fairford Rugby Club Berbera PUNTLAND Wajale Hargeisa Paul Holmes and Partner Frank Farquharson assisted SOMALILAND ETHIOPIA Fairford Town Council in 2018 in the preparation of SOMALIA their Neighbourhood Development Plan, by providing hard evidence to support the strategy for future housing Project highway and track of cyclone Sagar in May 2018 development. The WRA assignment focused on groundwater so that future development could be sited InfoWorks RS v16 was used for hydraulic models in appropriate places which are not subject to high which were calibrated against observed flood levels at groundwater levels in the Cornbrash limestone and river selected sites. Many of the large crossings were built as alluvium. Irish bridges which will be replaced with clear-span This involved both an inventory of old wells in the town Commemoration of William Dines area, and drilling of three new observation boreholes Frank Farquharson and Associate Nick Mandeville which were equipped with loggers. Drilling was done attended the unveiling of a blue plaque in Benson on 09 by GMD and CCGI under the supervision of Andy June 2018 to honour William Dines, the famous Dixon. The wells and boreholes were then monitored amateur experimental meteorologist. for six months. Groundwater hydrographs were modelled with reference to the national index site at Ampney Crucis, and other long-term monitoring sites, to predict 200- year return period maximum groundwater levels across the town area. F51D $06 5 5 10 $05 9 F51C F51B 95 -0.1 B5 $04 0 10 94.0 90 90 95 95 n/a n/a F51A 97.8 n/a 85 95 90 84 83 82 F39D 82 95 0 9 -0.6 F15 82 F35B 88.1 85 $03 81 F52 88.7 4 83 $02 8 F39C 0.5 F38 80 0 1.2 9 84.1 -0.2 83.3 A2 83.6 83.9 82.1 1.2 84.1 83 5 8 87.3 8 8 82 $01 86.1 -8.1 Blue plaque for W H Dines inaugurated in Benson on 09 88.5 F50 81 96.6 84 June 2018 0 9 83 F44 5 0 9 5 9 8 Scale in kilometres 84 0 0.2 0.4 0.6 0.8 1.0 Most UK hydrologists will be familiar with the Dines 0 57 3 5 © Crown Copyight: Ordnance Survey. Based on Mastermap data supplied by Centremaps CM-00670255_TIFF_1250-CM-00670255, with WRA Data superimposed 8 KEY Maximum predicted groundwater levels Development Hydrology Geology tipping bucket rain gauge, but for meteorologists he -8.1 Freeboard to GL F35B NP development options Zone 2 river flooding outline Alluvium 88.5 Ground Level 96.6 T200 max water level Areas which maintain at least FTC monitoring boreholes Head deposits invented a pressure tube anemometer, which could $01-06 1 m freeboard during T200 Dug-wells used for monitoring Negative freeboard indicates WL above Northmoor terrace deposits max groundwater conditions ground level, based on LiDAR data in mOD Spring Summertown-Radley terrace deposits measure wind direction and velocity with much greater T200 identifies 200-yr max groundwater level Groundwater Flow lines Cornbrash Limestone MAP SHOWING GROUNDWATER CONDITIONS AND SITE SUITABILITY Cornbrash -Kellaway boundary accuracy than previously, an instrument widely used subsequently for almost a century. He was also a Upper Lliw Reservoir in South Wales pioneer in the use of balloons and large box kites to Paul Holmes assisted Stillwater Associates in their measure upper air temperatures and pressures. One of reservoir safety work for Welsh Water, providing Dines’ associates at Benson from 1919 was Lewis F groundwater expertise for investigation of seepage in Richardson, the father of analytical weather forecasting. the Upper Lliw drawoff tunnel. The work involved On the day Frank Law, from CEH, recounted Dines’ geological mapping and chemical testing of seepage many inventions (www.oxfordshireblueplaques.org.uk water and sediment, to trace the origin of tunnel /plaques/dines.html), and former TV weather man Bill resurgence. Giles gave an amusing speech about the hazards of making early weather forecasts. New Associate Peter Baur has recently joined WRA as an Associate. He has a strong background in international development and hydrology in Africa, the Caribbean and Latin America, and brings technical skills in diverse areas of hydrology, hydrogeology and water quality, with a particular focus on the mining industry and due diligence. Inspection team (with staff from WRA, Stillwater Next WRA Board Meeting Associates, and Welsh Water) entering Upper Lliw Reservoir drawoff tunnel Friday 26th April 2019, Benson The WRA Bulletin is a quarterly publication, and relies on contributions submitted by Partners, Associates and Consultants. The document is circulated by email, and published on the WRA web-site, aiming to keep the WRA network up-to-date with respect to current activities. Please email contributions for future issues to Nick Mandeville: [email protected] Water Resource Associates LLP, PO Box 838, Wallingford, Oxon OX10 9XA. Tel: +44[0] 1491 838 190, www.watres.com Water Resource Associates – Bulletin - Issue No 51 January 2019.