We propose the novel integrated modelling procedure 3H-EMC for the determination of the environmental flow in rivers and streams; 3H-EMC combines Hydrological, Hydrodynamic and Habitat modelling with the use of the Environmental Management Classes (EMCs) that are defined by the Global Environmental Flow Calculator. We apply 3H-EMC in the Sperchios River in Central Greece, in which water abstractions for irrigation cause significant environmental impacts. Calculations of the hydrodynamic-habitat model, in which the large and the small chub are the main fish species, suggest discharge values that range from 1.0 m/s to 4.0 m/s. However, hydrological modelling indicates that it is practically difficult to achieve discharges that are higher than approximately 1.0-1.5 m/s. Furthermore, legislation suggests significantly lower values (0.4-0.5 m/s) that are unacceptable from the ecological point of view. This behaviour shows that a non-integrated approach, which is based only on hydrodynamic-habitat modelling does not necessarily result in realistic environmental flows, and thus an integrated approach is required. We propose the value of 1.0 m/s as the "optimum" environmental flow for Sperchios River, because (a) it satisfies the habitat requirements, as expressed by the values of weighted useable area that are equal to 2180 and 1964 m for the large and small chub, respectively, and correspond to 82 and 95% of their respective maximum values, (b) it is consistent with the requirements of Environmental Classes A and B, whose percentiles are higher than 75% for discharge (77.2%) and for habitat availability (>83.5% for the large chub and >85.0% for the small chub), (c) it is practically achievable from the hydrological point of view, and (d) it is higher than the value proposed by the Greek legislation. The proposed modelling approach can be applied to any river or stream using the same or similar modelling tools, which should be linked via suitable coupling algorithms.

Vegetation in river floodplains has significant influence on the flood hydraulics and fate of suspended sediments, nutrients and contaminants. In the present, work preliminary 3-D calculations were performed to examine the effect of vegetation on the mean flow in open channels using the CFD model CFX-12.1, employing the RANS k-epsilon turbulence model. Calculated flow velocity distributions were compared against an experiment of free surface uniform flow in a vegetated experimental channel, filled with cylindrical submerged elements representing vegetation; these elements were rigid and arranged in a staggered pattern.Four unstructured numerical grids were employed, ranging from approximately 9.5 to 27.5 millions of tetrahedral elements. The main characteristics of the flow were (a) the formation of small recirculation regions in the wakes of the cylinders and (b) the relative uniform flow conditions throughout the length of the channel. Low flow velocities were observed in the vegetated region, implying the resistance due to vegetation, and higher velocities close to the free surface. The best agreement with experimental data was achieved for the finest grid that also included grid refinement at the top of the cylinders. Grid independence behaviour using relatively very fine grids was rather surprising and requires further detailed investigation. KEYWORDS:Vegetation; eco-hydraulics; hydrodynamic models; turbulence models; fluvial hydraulics; river floodplains. INTRODUCTIONVegetation is one of the major factors that affect the mean and turbulent flow in open channels and the transport processes of suspended sediments and contaminants, thus determining the functioning of wetlands, such as river floodplains. In vegetated surface water bodies the resistance to flow is increasing and the mean flow velocities are reducing, relative to non-vegetated regions, due to the presence of aquatic plants. The interaction between the type of vegetation and the characteristics of flow field is of great interest for the design of flood defense systems and can be examined with the use of mathematical models.