Standing water is everywhere – but January and February are always wet months and floods are expected in many parts of the country. All low lying areas are at risk and expanses of water are evident on much of the flat ground. A study of the aftermath gives us valuable information from which to make plans for improvement.
Surface water finding exit
The passage of surface water flow becomes an interesting observation at the end of a rainy season. Water run-off is always localised with water finding the easiest route of exit. It is only when outfall restrictions cannot cope with the surface flow that flooding occurs. It is at these times that the benefit of a topographical study becomes of immense value. Routing surface water sounds simple but it is often neglected or calculations of water flow quantities are underestimated. The most important consideration must be the maintaining of adequate outfall locations. In low lying areas this becomes a difficulty and options can be limited to either boring down to permeable horizons or establishing a wet land sufficient to cope with all the surface water generated.
At times of heavy rains the marking out of low points on site becomes invaluable. Besides highlighting wet areas they serve to create the best route of reticulation needed in drainage provisions. Though exits do not become immediately apparent the direction of surface water flow can only be properly planned with a detailed contour plan.
The construction of shallow mowable swales directs water flow to safe outfall locations. These could be ponds, streams or ditches. The need for a ditch reticulation becomes very apparent after a rainy season and on the golf course ditches are invaluable at times of flooding with the swales bringing surplus water to a safe outfall. With this capacity peak flow off the site can be controlled to a degree. Swale installation can also enhance overall design creating mounding and undulations with excavated material. In diverting and concentrating surface water flow swales enable surrounding areas to remain firm and playable as well as maintaining sustainable conditions for growth in these areas.
Where run-off is restricted
Areas holding water soon result in deteriorating plant growth. This can result from a number of factors that become evident after considerable rain over an extended period. Limiting water penetration can be due to the excessive accumulation of thatch and organic matter at the surface which acts as an insulating material. This becomes readily apparent after persisting rain and highlights the need for reducing these factors. Notable too is the effect of compaction from foot traffic on wet ground and decompaction with the vertidrain or ‘earthquake’ when the soil has partially dried out gives grass growth renewed vigor.
The depth of grass cover relative the gradient is a prime factor in withholding surface water and it is fairly well established that gradients of at least 1:70 are needed to promote run-off on golf courses.
At the end of the winter months much can be learnt from the condition of golf courses and how they have performed after continual use – often in wet conditions. Surface drainage installations need annual assessment. The physical composition of the root-zone depth of topsoil gives an idea of the infiltration potential. Compaction and thatch may be overcome but the inherent soil and the gradient become limiting factors that can only be remedied with complete reconstruction. On golf greens with improved root zones these two factors are prime concerns too together with underground drainage installed. Where surplus water cannot be removed from low points anaerobic conditions develop and grass cover can weaken and die.