🏆 Trung Tâm Luyện Thi Chứng Chỉ Tiếng Anh Quốc Tế (IELTS · VSTEP · TOEIC · Cambridge · TOEFL/SAT)

Paragraph A For over a century, modern urban planning relied on a single hydraulic philosophy: channel rainwater away from streets as rapidly as possible using concrete pipes, storm drains, and impermeable asphalt. While this grey infrastructure proved effective during moderate rainfall, rapid urbanisation and intensifying monsoon patterns have exposed its critical flaw. When extreme downpours strike, sealed surfaces prevent natural soil infiltration, overwhelming drainage networks within minutes and triggering severe flash floods alongside acute groundwater depletion. Paragraph B In response, hydrologists and landscape architects—most notably Professor Kongjian Yu—championed the "sponge city" paradigm. Rather than treating stormwater as a hazard to be expelled, a sponge city functions as a living ecological buffer that absorbs, filters, retains, and gradually releases water. Permeable pavements, sunken rain gardens, bioswales, and restored urban wetlands work in concert to mimic pre-industrial hydrological cycles. During torrential rain, these green spaces capture up to 70 percent of surface runoff; during subsequent dry spells, the stored moisture evaporates to mitigate the urban heat island effect or recharges underlying aquifers. Paragraph C Despite compelling ecological benefits, scaling sponge infrastructure across densely populated megacities faces financial and institutional hurdles. Retrofitting historic downtown districts requires coordinating municipal water boards, transport agencies, and private developers—entities that traditionally operate in silos. Nevertheless, long-term economic modelling from pilot cities demonstrates that hybrid green-grey systems cost up to 30 percent less over a 25-year lifecycle than expanding underground concrete tunnels alone, while simultaneously increasing surrounding property values and urban biodiversity.