Drainage of Airport Surfaces - Some Basic Design Considerations

For determination of runoff from the flat turf surfaces encountered on the inter-runway areas of airports, a methodology is presented employing the newer knowledge concerning retention, infiltration, and overland flow. Since determination of supply rates is required, a detailed procedure is given that takes into account not only the fact that in nature antecedent precipitation within the storm reduces infiltration capacity values, but also the fact that in many storms rainfall rates are less at times than the related infiltration capacities. Within most turfed areas a peak-reducing pondage is available and practical procedures are developed for obtaining the outflow rates from the ponded areas. Two examples of design are presented. These illustrate that, once pipe sizes are selected and a hydraulic balance is achieved for runoff from rainfall of a selected frequency and duration, the capacity of a system varies but little for other frequencies or durations due to the relation of large changes in mass pondage to very small changes in depths.