Long-Term Management Policies of Reservoirs: Possible Re-Use of Dredged Sediments for Coastal Nourishment (original) (raw)
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Sustainability
Sedimentation has significant impacts on the useful capacity of an artificial reservoir, a resource to preserve. Interventions of dredging are therefore often unavoidable, even because decommissioning of dams is often impossible in many contexts and entails high costs. Dredging generates an undesired accumulation of materials that represent an environmental cost, but that could be used as intermediate products in other processes, such as beach nourishment. The study develops a method for the evaluation of the feasibility of an investment aimed at coastal nourishment with sediments dredged from artificial reservoirs. The method considers the set of technical conditions that make such use possible. The presence of economies of scope, with environmental diseconomies utilized as joint product, modifies the evaluation approach. The results of the approach show a possible environmental and economic sustainability of the proposed investment even in the presence of highly unfavorable scenar...
An Integrated Coastal Sediment Management Plan: The Example of the Tuscany Region (Italy)
Journal of Marine Science and Engineering
This paper presents the results of a study carried out to support the Region of Tuscany Coastal Sediment Management Plan, with the main aim of establishing the sediment budget considering the time span from 1981–1985 to 2005 for the 56 coastal sectors into which the 215 km-long continental sandy coast of Tuscany (Italy) was divided. The sand stability (according to a stability index) and colour compatibility (according to the CIEL*a*b* colour space with an acceptability range conforming to national guidelines) were determined in order to assess the possibility of using the available sediment in accreting sectors to nourish the beach in eroding areas. Only in two cases—i.e., the updrift of a harbour (at Viareggio) and in a convergence zone (at Marina di Pietrasanta)—are the volumes of sufficient magnitude to support a large nourishment project; however, the mean sand size is too small to guarantee efficient nourishment, even with medium-term stability. In contrast, the colour differe...
Some stretches of Latium coast subject to frequent erosion need repeated control actions to overcome the problem. Since 1999 " Regione Lazio " executed a beach nourishment program using " relict " marine sand located off Capo d'Anzio (Italy). ICRAM carried out a research to assess environmental impact of these activities by using different investigations before, during and after dredging. Side Scan Sonar and Multibeam investigations of sea bottom, sedimentological and biological studies and analyses on the water column were carried out during oceanographic surveys. One year later results showed changes in depth of the excavated area; grain size analyses indicate a textural variation but also a progressive recovery of the original characteristics. Changes in benthic community are clearly proportional to distance. There is no evidence of recovery even after one year. The whole study gave a methodological and scientific outline for future research on excavation ...
Land
This study, using different direct and indirect methodologies, evaluated the sedimentation rate in an artificial reservoir in central Italy. This reservoir is regionally representative and was built in the 1960s for hydroelectric purposes; it has experienced a strong decrease in trap efficiency and a loss of over 70% of the stored water volume. Direct measurements of the lake bottom bathymetry, carried out in 2006 and 2015, and 3D reconstructions performed in a GIS environment, made it possible to calculate the volume of filling material and to verify an increasing trend in the sedimentation rate since 2006. The sample reservoir denudation rate was compared with that obtained using the Revised Universal Soil Loss Equation method to calibrate the fundamental and critical factors of the method itself, and verify the contribution of a hydrological “direct” (through new channels or gullies) or “diffuse” (overland flow) connectivity. Furthermore, the comparison with the results obtained ...
2021
Sicily is a Mediterranean island-region, whose economy is based especially on tourism and also connected with beaches. Unfortunately, in the last fifty years about 2.5 km 2 of beach were lost due to erosion, causing damages worth approximately 5 billion Euros. At the moment about 300 km of the 1600 km of coast present erosion problems, 1/3 of which is threatening the economic and important historical assets as well as Sicilian cultural heritage. The Sicilian region decided to solve the issue, avoiding passive protection systems only used for urgent action, but instead adopting a Coastal Management Plan (CMP) aimed essentially at the use of soft protection systems, e.g. beach replenishment. In order to put into practice this type of intervention, thanks to a synergic collaboration with the CMP, a Borrow Deposits Plan (BDP) was drawn up, identifying three possible sources of materials: fluvial material, harbour dredging and submerged deposits. The detected deposits can be estimated in about 5 million m 3 of fluvial deposits useful for the pebbly beaches of the northeastern sectors, while the ones coming from harbour dredging, about 3 million m 3 , can be used only for local intervention. Submerged deposits located along the northwestern coast of the island have a strategic importance. They are situated at a depth of 100 m and are about 120 million m 3 , with excellent granulometric (fine and medium sands) and compositional features (quartz > 50%). It is clear that in order to better exploit the resources and above all reduce costs, it will be necessary to correctly manage the intervention, that will have to be carried out with the appropriate timing.
Sustainable management of sedimentary resources: a case study of the egadi project
Environmental Engineering and Management Journal, 2019
Multiple activities carried out on coastal areas expose marine sediments to contamination and their management has a great socioeconomic importance with a high impact on economic development of coastal areas. However, there is an increasing shift towards the use of more sustainable approaches for managing contaminated sediments. Using a case study of the Favignana Habour in Italy, this paper evaluates three approaches for the management of these sediments. The results of simulations carried out by SiteWiseTM software show that the use of contaminated sediment as filling material for Confined Disposal Facilities has lower environmental footprint than treatment and reuse of sedimentary resources on shore. The implications for these results for the development of effective policies and practices by all key stakeholders are discussed.
<Sediment management is becoming a critical issue around the world, particularly where the development of harbor facilities, the conservation of coastal environments and needs of tourism compete for sustainable use of sediment resources. <Determination of sedimentary budget along coast is essential, but not straightforward. Different sediment management option can determine input or output of material within the sediment sharing system. They often lay hidden by the different data source, due to the fact that national and local administration have different database related to their specific institutional responsibilities. Information and data need to be merged to have policy initiative, based on scientific principles and model for other jurisdictions, developing their own sediment quantitative estimation within an ICZM approach and a sustainable development of sedimentary resource's management, are needed particularly in coastal areas suffering erosion. The present paper represent a case study as it consider many restrictions due to contamination and compatibility issues related to beneficial reuse of sediments.
State of the art of reservoir sedimentation management in Spain
2000
Part of the total reservoir storage capacity in Spain (56 km3) is lost due to sedimentation processes taking place. Surveys carried out in 121 reservoirs indicate that 6% of them have undergone a capacity reduction of over 50%. However, most of them (81%) are characterised by a reservoir capacity loss below 20%. The most frequent methods used to control reservoir sedimentation in Spain fall into one of the following groups: reduction of sediment yield through basin management and removal of the sediment deposits that have built up. Reduction of sediment yields includes soil and water conservation programmes, upstream sediment trapping debris dams, and bypassing of sediment. In Spain, soil and water conservation programmes, mainly those involving afforestation practices and engineering measures, have been carried out since 1877. Flushing and excavation practices are being used to remove part of the sediment build-up from some reservoirs. With regard to this, the empty flushing of the...