Field measurement of bedload in a sand-bed river supplying a sediment starving beach

Billi, Paolo; Salemi, Enzo; Preciso, Emanuele; Ciavola, Paolo; Armaroli, Clara

doi:10.1127/zfg/2017/0466

Cited by 11 publications

(8 citation statements)

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“…the most effective for bedload transport. Though yearly variable, Q 10d , is in fact close to the threshold conditions for bed material entrainment in sandbed rivers of the northern Adriatic coast 11 ; moreover, that is the lowest duration flow data available in the official data records for the rivers of the region. On the base of yearly data, as the discharge exceeded 10 days a year ( Q 10d ) is close to the maximum discharge ( Q max ), and the higher is Q max the larger amount of sediment is likely to be delivered at the mouth.…”

Section: Methodsmentioning

confidence: 79%

The Po Delta is restarting progradation: geomorphological evolution based on a 47-years Earth Observation dataset

Ninfo

Ciavola

Billi

2018

Sci Rep

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From the 1950s, the Po delta, one of the largest anthropogenic world deltas, has been subjected to a fast degradation and shoreline retreat due a marked reduction of sediment supply, mainly controlled by human impacts/factors, including subsidence. Through the interpretation of satellite images, coupled with the analysis of the flow discharge, and of the annual frequency of marine storms, we show that recently (>2010) the Po River has resumed delta progradation, especially in its northern portion. This happens after decades of erosion, followed by alternating regrowth and degradation phases, indicating conditions of substantial stability (1970–2000). Today the delta shows aggradation of new mouth-bars at the main distributary mouth, a clear evidence of active constructive processes. The ongoing trend marks a countertendency compared to many deltas worldwide.

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Section: Methodsmentioning

confidence: 79%

The Po Delta is restarting progradation: geomorphological evolution based on a 47-years Earth Observation dataset

Ninfo

Ciavola

Billi

2018

Sci Rep

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“…The maximum channel width is about 60 m in the Fiumi Uniti and 30 m in the Savio case. The stream bed gradient is 0.00029 m/m in the Fiumi Uniti river [16] and 0.0003 m/m in the Savio. Bed material is principally sandy: D 50 is around 0.55 mm in the Fiumi Uniti and around 0.50 mm in the Savio (i.e.…”

Section: Fig 1 Study Area With Location Of the Main Artificial Strumentioning

confidence: 94%

“…Unfortunately, information about the sediment transport of Emilia-Romagna rivers is limited and restricted to a small number of them [13,14,15,16]. In order to enlarge the existing sediment supply dataset, bedload measurement campaigns in representative rivers have been carried out by the authors.…”

Section: Introductionmentioning

confidence: 99%

Field data and regional modeling of sediment supply to Emilia-Romagna’s river mouths

et al. 2018

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The Fiumi Uniti and Savio rivers are two small sandy-bed river systems which sediment yield contributes feeds part of the Emilia-Romagna beaches (Italy). Since the twentieth century the northern Adriatic coast has been affected by well-known beach retreat phenomena. As the sediment supply of these local rivers is not well known, an analysis of bed-load transport rates for the last 10 kilometres of the river has been done. Multiple analysis, supported by direct field measurements of the 2005-06 and 2017 years (still ongoing) have been realized. Complementary hydraulic investigation and modelling have been performed. Repeated bed-material samplings have been carried out during different flood conditions, obtaining a significant number of observations. Aiming at defining the behaviour of sediment-transport in these two rivers, this paper focuses on the analysis of threshold sediment transport condition. Several formulae available in literature were used to test the field measurements. All these criteria seem inappropriate to predict the threshold conditions for bed particle entrainment in terms of the value of bed shear stress. The inaccurate estimation given by these formulae is due to the fact that they do not consider natural grain-shape factors or are mainly suitable for gravel-bed rivers.

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“…However, these datasets generally refer only to suspended sediment loads; bedload information is actually missing for river sections in alluvial plains close to the mouths. Notable exceptions are the Reno (Preciso et al, 2012) and Fiumi Uniti rivers (Billi et al, 2017), in the study region where the Savio is located. The current paper has the following aims: (i) to evaluate bedload sediment transport through direct measurements during river floods; (ii) to identify bedload sediment input at the river mouth, identifying moments of effective sediment transport; (iii) to quantify the sediment budget of the river mouth; (iv) to propose a short to medium term sustainable management strategy, considering the local demand of sediment for beach replenishments.…”

Section: Introductionmentioning

confidence: 96%

Sedimentation at River Mouths bounded by Coastal Structures: A Case Study along the Emilia-Romagna Coastline, Italy

Grottoli

Cilli

Ciavola

et al. 2020

Journal of Coastal Research

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Beach retreat in the Emilia-Romagna coast, facing the north Adriatic Sea, is well-known since decades and several factors are behind this phenomenon: a scarcity of natural sediment supply by rivers, natural and anthropogenic subsidence, and a strong urbanization of the coastal zone. Several bedload measurement campaigns in one representative river of the Ravenna province (Savio River) have been carried out since 2017. At the same time, seasonal surveys of bathymetry were undertaken at the river outlet to correlate changes in sedimentation with river input. The river mouth is constrained by artificial embankments that possibly funnel out sediment offshore during river floods. However, monitoring of bedload transport correlated with bathymetric changes between July 2017 and November 2018 still found a positive budget of almost 5000 cubic meters. Local authorities in Ravenna are planning to dredge 20000 cubic metres from the river mouth to supply small nourishments outside the studied coastal cell. According to the measurements of bathymetric changes, the Savio mouth will need almost six years to recover, assuming the occurrence of a particularly efficient rate of sediment transport, like the one observed in the monitored period. Notably, the analysed period included a very large river flood that could overshadow the modal sediment transport operated by the river. Furthermore, with deepening of the mouth, the two villages adjacent to the outlet are likely to become more exposed to sea flooding, due to the propagation of surges inside the river mouth. The paper concludes that dredging activities should be reconsidered in view of the precarious equilibrium of the system.

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Field measurement of bedload in a sand-bed river supplying a sediment starving beach

Cited by 11 publications

References 0 publications

The Po Delta is restarting progradation: geomorphological evolution based on a 47-years Earth Observation dataset

The Po Delta is restarting progradation: geomorphological evolution based on a 47-years Earth Observation dataset

Field data and regional modeling of sediment supply to Emilia-Romagna’s river mouths

Sedimentation at River Mouths bounded by Coastal Structures: A Case Study along the Emilia-Romagna Coastline, Italy

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