Technical
Even with the highest annual rainfall ever recorded, the failure in sports pitch drainage must give concern. Time and again assessments of poorly drained and muddy sites are made - the most common situation being the collection of surface water on pitches that are unable to promote any degree of surface drainage. Strange, after so much has been said and written on drainage installation techniques - particularly related to slit drains and grooving - standards of installation have reached new levels and current specialised equipment has become so efficient
Consultant, Gordon Jaaback, offers his views on the subject
important consideration. Water lingering on the surface of heavy clay topsoiled pitches becomes a scourge to footballers. This water must be removed as soon as possible - at least before firm playing surfaces becomes soft muddy quagmires. Rainfall becomes a vital consideration, and it is the intensity and duration that is most important. Wallingford research (FEH,1993) rates the occurrence of in the region of 25mm in one hour to be the maximum intensity expected over a ten year period in central and southern England.
D
It may be startling to some that over 80% of rainfall in the south is less than 10mm per day, with up to 50% being less than 2mm per day. Nevertheless, although average rainfall intensity in Britain is in the region of 5mm per hour, short duration heavy downpours in five to ten minutes can far exceed this rate falling at up to 100mm per hour. This is especially significant with the realization that rain can fall on average twelve days
rainage is more than installing pipe and slit drains -
understanding how surface water moves both on and below the surface is probably the most
in the month during the winter season when, for much of the time, the surface soil is saturated and evapotranspiration is negligible (Jaaback,2008).
Impact of water moving over and above the soil surface (run-off)
Naturally, on commencement of rainfall, there is water retained in the turfgrass foliage, the micro-depressions within the soil surface and porous surfaces to drain installations. Estimates of the water retained have not been researched, but it is expected that they could amount to between 3mm and 5mm. What is certain is the fact that rainfall must exceed the retained amount before run-off commences (Tindell and Kunkel, 1999). Secondly - and often overlooked - water run-off on to the pitch from higher ground always results in wetter areas. This flow must be diverted above the cut slope, if it exists. A practical measure to halt the movement of water over the soil surface is the installation of ditches and swales. The latter can become an integral means in attenuation (CIRIA,2000). In preventing run-off on to the pitch, shallow mowable swales at the base of cut slopes have proved very effective - particularly
Sports Pitch Drainage
Why are there still failures?
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