Management for sustainable river valleys requires balancing their natural values against the need for agricultural and recreational development on surrounding lands. The Southern Całowanie Peatland near the city of Warsaw sits on a sandy terrace and has well preserved Carex and Molinia stands existing in part of the area, especially where water tables are less than 1.5 m below the surface. The existing drainage network in this southern part has been poorly maintained and could be reestablished to help raise water levels for restoration of the peatland. Modflow was used to look at influence of drainage channel water levels on the overall water table height in the area. By raising water levels in the drainage system by 0.5 m it was found that 29% of the area would become suitable for increasing Carex and Molinia communities.
Gradient-based implicit similarity functions are derived theoretically from a few variants of the Mellor-Yamada algebraic turbulence-closure model under assumptions of local equilibrium conditions in a stably stratified shear flow. The solutions are compared with empirical functions presented by Sorbjan. Good agreement is found in the range of gradient Richardson number Ri extending up to around 0.2. The gradient-based scaling framework offers better accuracy and reliability than the traditional Monin-Obukhov framework, as it circumvents the problems of small values of fluxes and cross-correlations. It is also possible to separate the specification of the master length-scale from the calculation of similarity functions describing second moments and dissipation rate. The related discussion of model performance at higher Ri is included. It is unclear whether the current countermeasures against spurious flow decoupling reflect the observed features of turbulence in the very stable regime, due to the apparent breakdown of the Richardson-Kolmogorov energy cascade, as found by Grachev et al.
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