A methodology to evaluate the effects of river sediment withdrawal: The case study of the Amendolea River in southern Italy

Abstract

Sediment deposition is an issue affecting many rivers. To oppose it, sediment withdrawals are often used. However, this practice can trigger further problems in river and coastal sections but, on the other hand, periodic removal of deposited sediments can reduce flooding risk. Also, these sediments can be used for beach nourishment. Therefore, before carrying out a sediment withdrawal, it is necessary to analyze the whole basin to evaluate the consequences for the sediment balance. This paper describes a methodology to evaluate the effects of river sediment withdrawals through a case study on the Amendolea River, a torrential river in southern Italy. In particular, the methodology is divided into three main phases. The first phase was developed with GIS software in order to perimeter and to morphometrically characterize the river basin and its hydraulically and sedimentologically homogeneous sub-basins. The second phase was developed using the HEC-HMS software in order to evaluate the hydrological balance of the basin and its sub-basins. The last phase was developed using the HEC-RAS software (through the SIAM model) in order to identify the areas in erosion, in deposition and in equilibrium. Moreover, through this model is possible to identify the sections where sediments can be withdrawn, and to estimate the possible morphological river changes due to withdrawals. In this case study, the sediments will be taken from the sections where the bottom has elevations near or above those of adjacent lands, such as to increase the flooding risk. Sediment withdrawals will be taken without eroding the bottom and at a distance from the river banks that does not unstabilize them. Finally, the methodology described in this paper is based on the joint use of various open source software and can be used in any other river with hydrological regime similar to the Amendolea River.

The Effects of Anthropogenic Pressure on Rivers: A Case Study in the Metropolitan City of Reggio Calabria

“…However, the levees are often not continuous and missing parts that should be filled with a high priority. Furthermore, almost all the levees were built in the years between the 1950s and 1970s so their functionality should be verified considering possible morphological changes of the riverbed, for example, over-flooding that is frequent in Calabrian rivers [78], and climate change [108][109][110][111]. The interventions of cleaning and reshaping the riverbed should be carried out at least annually, due to the high solid transport during flood events that is frequent in Calabrian rivers and due to the frequent presence of dense vegetation, as visible in the Calopinace River, especially where there are obstructible culverts, as occurred in the Gaziano River.…”

“…This combination of hydrological and granulometric characteristics often causes high solid transport and erosion capacity, with consequences on the valley parts and on the mouths. In the valley parts, aggradation is often observed due to the sedimentation of the solid material caused by the reduction of the slope [78]. Therefore, the solid material that reaches the mouth contributes significantly to the shoreline evolution [79][80][81].…”

Beach and Dune Erosion: Causes and Interventions, Case Study: Kaulon Archaeological Site

“…Longterm variations are correlated to alterations in coastal, wind, and river sedimentary balance [13][14][15][16]. Often these alterations are caused by anthropogenic factors such as the construction of buildings, infrastructures, ports and coastal defense works in coastal areas [17], and the construction of hydraulic structures interfere with fluvial dynamics such as levees, dams, and inert drains from riverbeds [18,19]. On the other hand, the short-term variations are mainly related to natural factors such as single sea storm [20], cluster of sea storms [21,22], extreme flood events [23], or concurrent events [24][25][26] which cause coastal flooding [27].…”