A labyrinth weir allows for higher discharge capacity than conventional linear weirs, especially at low hydraulic heads. In fact, this is an alternative for the design or rehabilitation of spillways. It can even be used as a strategy in problems related to dam safety. A sequential design method for a labyrinth weir is based on optimal geometric parameters and the results of discharge flow analysis using Computational Fluid Dynamics and the experimental studies reported in the literature. The tests performed were for weirs with values of H_T/P ≤ 0.8 and for angles of the cycle sidewall of 6° ≤ α ≤ 20°. The results of the discharge coefficient are presented as a family of curves, which indicates a higher discharge capacity when H_T/P ≤ 0.17. Four aeration conditions are identified with higher discharge capacity when the nappe is adhering to the downstream face of the weir wall and lower discharge capacity when the nappe is drowned. Unstable flow was present when 12° ≤ α ≤ 20°, with a greater presence when the nappe was partially aerated and drowned. The interference of the nappe is characterized and quantified, reaching up to 60% of the length between the apex, and a family of curves is presented as a function of H_T/P in this respect. Finally, a spreadsheet and a flowchart are proposed to support the design of the labyrinth type weir.

Freshwater flocculation in the Usumacinta River delta during the high flow season was confirmed and supported by field data and the results from experiments conducted in a rotating annular flume and in a settling column device. Although the stream intensity and a bottom macroform generated and disturbed the 3D turbulence components in the cross section, the flow patterns followed the logarithmic law and the Nezu and Nakagawa models. The Rouse model can be applied to predict suspended sediment flux; however, flocculation led to diffusivity ratios less than 0.63 and effective settling velocities close to $1\mathrm{mm}/\mathrm{s}$ that were consistent with the mass conservation equation. When comparing the suspended load patterns of several lowland rivers, flocculation stages are related to shear rate; furthermore, in contrast to saline environments, the representative aggregate size in freshwater systems is presumably higher than the Kolmogorov microscale.

Particle aggregation modifies sediment dynamics, which is a determining factor for morphodynamic and ecological processes in deltaic plains. Here, we investigated the link between intra-annual hydrodynamics variability and flocculation in the Grijalva-Usumacinta system. Monthly (2016–2017) and seasonal (2021–2022) river data was processed using analytical methods and the simplified sonar equation. Flocs were reformed and characterized in the laboratory, validating the in situ settling velocities (0.5–3.8 mm/s) and the existence of large low-density macro-flocs (>300 μm). We verified that flocculation prevailed, exhibiting seasonal patterns; (1) the highest aggregation rates matched the increase in total suspended solids at rising-flow (>100 mg/L), (2) periods of high-flow showed stable aggregation rates, and (3) an influence of marine conditions occurred at low-flow. Particulate phosphorous and organic fraction showed seasonal patterns linked to flocculation. Due to damming, the shear rates varied slightly (7–11 L/s) in the Grijalva, leading to high flocculation intensities affecting the diffusivity ratio. In the Usumacinta, aggregation was limited by shear rates that normally exceed 15 1/s. We found seasonal Rouse parameters representative of sediment dynamics.