Storm water management: Potential for lower cost and more benefits if farmers and municipalities cooperate on tile drainage

THE PROBLEM AND CURRENT COSTS OF ITS SOLUTION When water tables rise to the surface, additional rain runs off. Since an inch of runoff from a 4,000 ha (10,000 ac) watershed amounts to 1,027,290 m³ (36,300,000 ft³) of water, such runoff becomes an engine of flooding and destruction if it comes off quickly. Attractive stream frontage becomes a menace when the stream's turbulent surface rises 3 or 4 m (10 or 13 ft), floods basements, and pushes buildings off their foundations. Following such “once in a hundred year” events, diligent municipal managers commonly evaluate the damages and seek solutions that can prevent such damage in the future. The common solution is to construct one or more stormwater detention basins between the source of the runoff water and the area where the runoff water will do the most damage. Water detained in such basins is released at rates which will not cause significant damage downstream, but will empty the basin to restore its detention capacity within a few days, as indicated by the red line in figure 1. Costs of buying the land for and constructing such stormwater detention basins have ranged from about US$18 to US$35 m^-3…