Objectives The urban floods occurred in 2013 and 2016 exposed the serious shortages of Wuhan infrastructures to resist weathering disasters. Traditional drainage of Wuhan against urban flood enfaces the challenges due to the sharp decrease of water area. A large amount of rainwater flows into the Yangtze River, aggravating the downstream flood.
Methods A new strategy is proposed to control the urban rainwater by using the "thirsty" soil to absorb rainwater. The expansion of soil moisture characterizes the water absorption capacity of soil. In principle, the saturated soil expanses and raises ground surface; on the contrary, the thirsty soil shrinks in volume and results into ground subsidence. It becomes a better strategy to control urban flood by utilizing this absorption capacity of thirsty soil, not only transforming the rainwater disaster into water resources, but also improving the ecology of urban pedosphere. The natural fluctuation of urban ground deformation is measured to roughly estimate the potential capability of water absorption. We took use of InSAR (interferometric synthetic aperture radar) data and 110 datum points in Wuhan center to inverse the surface deformation during the temporal window of 2015-04 to 2016-04.
Results The measured results demonstrated that the uplift of Wuhan urban area reached 18 mm/a. The current drainage capacity of Wuhan is equivalent to 140 mm/d rainfall, the water capacity of lakes is 250 mm/d rainfall, and the flood resistance capacity of soil sponge is only 30 mm rainfall. If soil's water absorption capacity is fully utilized, the soil sponge of 10 m soil layer can absorb 4 500 mm/d rainfall.
Conclusions The uplift of the urban land surface was caused by physical and chemical expansions of soil water; its potential capacity of flood control is much bigger than other methods. In addition, the zonings of surface rise indicate the runoff directions of the groundwater.
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