It did occur to me that the 'flood' issue was real - significant rainwater runoff from the hangers, taxiways and inter-hangar apron areas appears likely during heavy rain.
One innovative solution would be to capture the rainwater from the hangar roofs to use for washing the aircraft. It wouldn't take much more than some very large water butts and appropriate filters and first-flush devices. (see
http://www.rainharvesting.com.au/fir..._diverters.asp) This might reduce the water rates for the airfield, and would reduce the drainage requirements by roughly half. Other drainage measures such as a drainage system with a significant internal storage capacity could also help alleviate any flooding risk.
Best Wishes
tp