River Morphology, Channelization, and Habitat Restoration

Abstract

Authorities and planners involved in river restoration projects often tend to focus on the hydromorphological state of a short river reach or certain aquatic habitats where the pending deficits are most evident. Nevertheless, for long-term and sustainable restoration, one should also consider flood dynamics and other interlinked processes at larger spatiotemporal scales, ideally at the catchment scale. Moreover, restoring river morphology also calls for the consideration of the dynamic processes of the whole fluvial system, including the adjacent floodplains, with its diverse interactions between the physical environment (morphology, flow, sediment, etc.) and the riverine coenoses (compare EU Water Framework Directive 2000). Various concepts in river morphology and ecology address fluvial systems as hierarchical arrangements that integrate typical geomorphic and ecological features over a range of spatial scales. Such well-established schemes are, e.g., the Hierarchical Framework of Stream Habitats (Frissell et al. 1986), the Hydrosystem Approach (Petts and Amoros 1996), the Hierarchical Patch Dynamics Model (Wu and Loucks 1995), the River-Scaling Concept (Habersack 2000), or the Riverine Ecosystem Synthesis (Thorp et al. 2006). They have in common that riverine structures at the local scale are viewed as habitats nested in larger systems at reach scale or catchment scale.

Environmental filtering governs the spatial distribution of alien fishes in a large, human‐impacted Mediterranean river

“…Interestingly, while Batalla, Gómez, and Kondolf () and Radinger, Alcaraz‐Hernández, et al () revealed that hydrologic alteration in the Ebro basin is most pronounced in downstream proximity to dams, our results revealed highest numbers of alien species in 25–60 km distance downstream of dams. The ultimate reason for this downstream shifted effect remains unclear, but might be related to the so‐called “rhithralization” effect (Hohensinner, Hauer, & Muhar, ). By that, reaches immediately downstream of dams may show relatively elevated flow velocities and larger grain sizes of the substrate, which might benefit the native rheophylic, lithophylic species (e.g., Ebro barbel) rather than the limnophilic alien species (e.g., largemouth black bass [ Micropterus salmoides ]).…”

Symbiosis between river and dry lands: phycobiont dynamics on river gravel bars

“…River gravel bars are dynamic and heterogeneous habitats ranging from glacial floodplains and alpine wide river valleys to piedmont (Montgomery and Buffington 1998; Malard et al 2006; Tockner et al 2006; Hohensinner et al 2018). Periodical floods together with variation of speed and intensity of the water current, model richly braided channels with a mosaic of channels, pools, bars and islands (Junk et al 1989; Tockner et al 2000; Ward et al 2002).…”

Evaluation of the Methodology to Assess the Influence of Hydraulic Characteristics on Habitat Quality

“…Further research [15] compared the differences in geomorphology between natural and regulated streams and their impact on biota, since natural channels differ from prismatic ones by their rich variability of the cross-section (XS) and longitudinal channel profiles. Typical consequences of geometrical river regulations for the biota are the reduction of original instream habitat complexities and habitat availabilities in increasingly uniform riverbeds [21]. It is the morphology of such regulated rivers that is the main reason for the loss of biota and the degradation of the value of the river.…”