Dam placement cuts flood peaks; coalfield and Baltic models separate mechanisms
Optimised detention dams reduced modelled flood peaks. Separate models divided subsidence at one coalfield between mining and groundwater and sorted three decades of Baltic change into six regimes.
Science··Evening
Optimised detention dams cut peak flow by up to 83 per cent
A two-layer method selected the location and size of distributed detention dams in the non-urban part of a watershed by weighing downstream peak flow, runoff volume reaching the city and construction cost together. It then added a control layer that set gate operation before a storm. Peak flows fell by up to 83 per cent in the modelled basin, with more efficient use of existing storage providing added protection without larger structures. Because the result belongs to one mixed urban-natural watershed and a defined set of storms, 83 per cent cannot be treated as a general flood-reduction rate.[1]
Mining's share of subsidence reaches 62.4 per cent at Xuchang
A hydro-mechanical model of the Xuchang Coal Mine separated the effects of mining and groundwater pumping, which are usually counted together. From 2018 to 2020, the model assigned an average 62.4 per cent of total subsidence to coal extraction and 37.6 per cent to groundwater pumping. Mining was associated with larger and faster surface drops, while pumping was associated with smaller and slower ones. The shares varied across the site and over time, so one attribution cannot be carried to another year or working panel. At current extraction rates, the model projected no new large subsidence funnel at the site over the next five years; the result cannot be generalised to other coalfields.[2]
Three decades of Baltic profiles divide into six hydrographic regimes
An unsupervised neural classifier sorted monthly temperature and salinity profiles from a Baltic Sea ocean reanalysis spanning 1993 to 2023 into six hydrographic regimes. The regimes range from colder and fresher conditions to warmer and saltier ones, and their timing aligns with known major inflows from the North Sea. Salinity remained the main control on density structure, while the thermal contribution grew in more recent regimes. Because stratification influences vertical mixing and deep-water renewal, it matters for how much oxygen reaches the Baltic's deep basins. The study diagnoses a reanalysis product and does not provide a forecast.[3]
