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A detailed review and chronological survey is presented of the various techniques which have been used for the measurement of river bank erosion and channel change. The techniques are classified according to the time scales involved (long, intermediate and short) and each is discussed with respect to accuracy and repeatability. The methods covered include sedimentological evidence, botanical evidence, historical sources, planimetric resurvey, repeated crossprofiling, erosion pins and terrestrial photogrammetry. Prospects for future developments are also discussed.

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This paper evaluates the relationships between atmospheric circulation, climate and streamflow in the northern North Atlantic region over the last century and especially the last 50 years. Improved understanding of climatic influences on streamflow is vital given the great importance of fluvial processes to natural systems and water resources, especially in the light of recent and predicted climate change. The main focus lies with climatic and hydrologic implications of the major circulation patterns in the northern North Atlantic, namely the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). The studies reviewed here reveal key relationships between circulation, climate and streamflow across the northern North Atlantic, allowing the construction of a simple conceptual model for this system. Generally positive NAO/AO-streamflow relationships are found in northwest Europe and northeast USA, with both positive and negative NAO/AO-streamflow linkages apparent for parts of eastern Canada. To help promote a better understanding of the system, several research gaps are identified and critically examined, including: the spatial scope and coverage of investigations; data quality and homogeneity; appropriateness of analytical techniques; and the need for greater knowledge and technique sharing between hydrology and climatology, particularly regarding the rigorous characterization of atmospheric circulation patterns. Among these, the development of seasonally varying, or mobile, NAO indices, to capture variations in subseasonal, seasonal and annual movements in the centres of action, and the need to develop analyses of more hydrologically meaningful climate variables beyond conventional time averaged statistics, are deemed particularly important.

Original citation: Dieppois, B. , Pohl, B. , Rouault, M. , New, M. , Lawler, D. and Keenlyside, N. (2016) Interannual to Interdecadal variability of winter and summer southern African rainfall, and their teleconnections. Abstract This study examines for the first time the changing characteristics of summer and winter southern African rainfall and their teleconnections with large-scale climate through the dominant time scales of variability. As determined by wavelet analysis, the austral summer and winter rainfall indices exhibit three significant time scales of variability over the twentieth century: interdecadal (15-28 years), quasi-decadal (8-13 years), and interannual (2-8 years). Teleconnections with global sea surface temperature and atmospheric circulation anomalies are established here but are different for each time scale. Tropical/subtropical teleconnections emerge as the main driver of austral summer rainfall variability. Thus, shifts in the Walker circulation are linked to the El Niño-Southern Oscillation (ENSO) and, at decadal time scales, to decadal ENSO-like patterns related to the Pacific Decadal Oscillation and the Interdecadal Pacific Oscillation. These global changes in the upper zonal circulation interact with asymmetric ocean-atmospheric conditions between the South Atlantic and South Indian Oceans; together, these lead to a shift in the South Indian Convergence Zone and a modulation of the development of convective rain-bearing systems over southern Africa in summer. Such regional changes, embedded in quasi-annular geopotential patterns, consist of easterly moisture fluxes from the South Indian High, which dominate southerly moisture fluxes from the South Atlantic High. Austral winter rainfall variability is more influenced by midlatitude atmospheric variability, in particular the Southern Annular Mode. The rainfall changes in the southwestern regions of southern Africa are determined by asymmetrical changes in the midlatitude westerlies between the Atlantic and Indian Oceans.