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Abstract Mega-blowouts are very large-scale deflationary landforms, formed by wind erosion. They are abundant in the Gonghe basin, northeast margin of the Qinghai-Tibet Plateau (QTP) and little is known about the evolution, dynamics or controls on the mega-blowout development. Here we report on mega-blowouts' morphodynamic expansion rates based on 4 years of monitoring. Also presented is a remotely sensed longer-term (48 years) morphologic change record which is used to understand the initiation, growth and evolution of mega-blowouts in alpine grasslands. Links between the morphodynamics and blowout-controlling factors are analysed. The expansion rates of the monitored blowouts vary according to blowout area, with different parts of the blowouts expanding at different rates. Generally longitudinal (downwind) mega-blowout expansion is greatest, with upwind headwall expansion via collapse being particularly significant. The growth of depositional lobes downwind of mega-blowouts tends to be faster than growth of the deflation basins. Merging of adjacent blowouts is one of the key mechanisms for mega-blowout development and extension. Sediment characteristics, wind erosion, water erosion, and freeze-thaw processes also all play a part in mega-blowout initiation and expansion. However, the relative roles that these factors play may differ according to a blowout's evolutionary stage. Due to an almost unlimited depth of sand, very low water table, and short grass vegetation cover, evolution into parabolic dunes is limited. A large proportion of sand patches and small blowouts around the mega-blowouts are still developing in the Gonghe basin proving that land degradation is still ongoing. Future work will focus on the feedback mechanisms between the blowout morphodynamics, climate change and anthropogenic impacts. [ABSTRACT FROM AUTHOR]

Evolutionary trajectories and related control factors of the Fortore River (southern Italy) are analyzed over a 150-year period as to assess channel modifications. A multitemporal GIS analysis of topographic maps and aerial photographs together with topographic and geomorphological field surveys were performed. Attention was focused on the impact caused by human disturbance, above all the presence of the Occhito dam at only 40 km upstream of the Fortore mouth (central Adriatic coast). Results show that channel adjustments occurred in three distinct phases and were primarily driven by human disturbance that diversely affected reaches located upstream and downstream of the dam. From the last decades of the nineteenth century to the 1950s (phase 1), channel widening prevailed along upstream reaches whilst narrowing along downstream reaches. Major channel adjustments occurred from the 1950s until the end of the 1990s (phase 2), especially channel narrowing of up to 81% in upstream reaches and 98% in downstream reaches. Narrowing was accompanied by channel-bed lowering of 1 to 5 m and by pattern changes in prevalence from multithread to largely prevailing single-thread channel configurations. In-channel mining, channel works, and hydraulic interventions are considered key driving factors of observed channel adjustments. The closure of the Occhito dam in 1966 had significant and permanent effects on downstream reaches through overall discharge regulation and permanent sediment trapping as also proved by the progressive retreat of the Fortore river mouth area. From 2000 to 2015 (phase 3), a substantial trend inversion was observed with overall channel widening and partial aggradation of upstream reaches and total stabilization of downstream reaches. As highlighted by an integrated multitemporal analysis of recent channel changes and flood events, the latter have played an important role in channel recovery of upstream reaches. Comparison between the Fortore River and other rivers in southern Italy has allowed us to ascertain that the reconstructed evolutionary trajectories are quite similar and that control factors are essentially the same. In particular, it confirms the role of major hydraulic structures as to the amount of channel adjustments of downstream reaches and the ensuing scarce to nil potential to channel recovery of regulated reaches. [ABSTRACT FROM AUTHOR]

Since the last decades of nineteenth century, Italian rivers experienced remarkable morphological changes. Most of the previously investigated river channels were affected by intense human disturbances, which were frequently indicated as the main control factor. In contrast, the Tammaro River (southern Italy) underwent less complex human interventions than other Italian rivers, at least since the recent closure of the Campolattaro Dam in the median zone of the catchment. Thus, it represents a good example to analyze the effects of changes in climate and land use on short-term channel adjustments. In this paper, the channel adjustments experienced by the Tammaro River over a period of ~140 yr (1870–2011) were investigated. The study integrated results from GIS-based geomorphological and land-use analysis, field surveys, and analysis of hydrological data (rainfall, flow discharges, extreme floods). From the last decades of nineteenth century to the mid 1930s, the river experienced widening and a slight increase in transitional channel morphologies (Phase-1). From the 1930s to the late 1990s, the river underwent a marked narrowing and limited to moderate incision (Phase-2). The geomorphological effects of the 1949 extreme flood were superimposed on the Phase-2 response. Finally, from 1990s onwards (Phase-3), the river experienced substantial stability with respect to the changes during the previous phases and different behaviors at the reach scale. During Phase-3, changes in channel morphology were observed a few years after the closure of the Campolattaro Dam. The morpho-evolutionary phases observed for the Tammaro River were very similar, even if slightly diachronous, to those reported in the literature for more anthropized rivers of southern Italy. • The Tammaro R. (Southern Italy) underwent negligible in-channel human disturbances, at least since 2006. • In 141 years, it experienced three phases of remarkable channel changes. • These changes were fully comparable with those of more anthropized rivers. • Main control factors were extreme floods, decadal rainfall changes, land-use changes. [ABSTRACT FROM AUTHOR]