TOEFL ITP Reading set 029
Reading Comprehension practice — read the passage and choose the best answer.
การฟื้นฟูพื้นที่ชุ่มน้ำกับการดักตะกอน
- Line numbers appear every 5 lines.
- Answer all 10 questions, then choose ตรวจคำตอบ to see the Thai translation, score summary, and explanation.
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Wetland managers restore marshes and floodplains partly because
dense vegetation and shallow water slow river currents. As flow
velocity drops, suspended silt and clay settle onto the wetland
floor instead of racing downstream toward deltas or coastal
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channels. That sediment trapping rebuilds elevation lost to
erosion or subsidence and can reduce the sediment load that
might otherwise clog harbors or bury coral reefs offshore.
Roots and stems further stabilize newly deposited mud, while
microbial films bind fine particles so they resist the next
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high-water event. Engineers therefore design restoration sites
with gentle gradients, planted corridors, and openings that
admit flood pulses without scouring the entire bed. Monitoring
teams measure accretion with marker horizons and elevation
rods, comparing rates before and after replanting. Results
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vary: some restored marshes accumulate several millimeters of
sediment each year, while others trap little when upstream dams
already hold most of the river's load. Seasonal timing also
matters; spring floods may deliver most of the year's sediment
in a few weeks, leaving quieter months with little deposition.
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Critics note that trapping is not always benign. Overly
efficient wetlands can starve downstream beaches of sand needed
for natural shoreline defense, so planners must balance local
accretion against coastal sediment budgets. Contaminated
particles from industrial watersheds may also settle into
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restored marshes, requiring soil testing before sites become
wildlife habitat or community parks. Still, when rivers carry
healthy loads of clean sediment, restored wetlands act as
living filters that rebuild land, buffer floods, and store
carbon in organic soils that form over decades of plant growth.
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Policy documents increasingly treat sediment trapping as a
measurable restoration goal alongside biodiversity and water
quality targets for regional watershed plans. Understanding how
plants, hydrology, and sediment supply interact helps managers
choose sites where trapping will support, rather than
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undermine, broader coastal resilience across linked ecosystems.