Journal of Marine Science and Engineering Article Beach Nourishment Alternatives for Mitigating Erosion of Ancient Coastal Sites on the Mediterranean Coast of Israel Menashe Bitan 1, Ehud Galili 1,2, Ehud Spanier 1,3 and Dov Zviely 4,* 1 Department of Maritime Civilizations, The Leon H. Charney School for Marine Sciences, University of Haifa, 199 Aba-Khoushi Avenue, Mount Carmel, Haifa 3498838, Israel; [email protected] (M.B.); [email protected] (E.G.); [email protected] (E.S.) 2 Zinman Institute of Archaeology, University of Haifa, 199 Aba-Khoushi Avenue, Mount Carmel, Haifa 3498838, Israel 3 The Leon Recanati Institute for Maritime Studies, The Leon H. Charney School for Marine Sciences, University of Haifa, 199 Aba-Khoushi Avenue, Mount Carmel, Haifa 3498838, Israel 4 Faculty of Marine Sciences, Ruppin Academic Center, Emek-Hefer 40250, Israel * Correspondence: [email protected]; Tel.: +972-9-830-4149 Received: 26 June 2020; Accepted: 10 July 2020; Published: 12 July 2020 Abstract: Since 2011, beach nourishment has become the preferred solution for mitigating coastal erosion along the Mediterranean coast of Israel, as it is considered “soft” and environmentally friendly. However, using fine sand for nourishment in Israel without supporting measures is problematic due to the high wave energy and strong longshore currents in the littoral zone that tend to drift the sand away. This would require ongoing, multiyear, costly, and never-ending maintenance. In the present study, we analyzed sand and pebble alternatives for nourishment of the eroded beach in front of Tel Ashkelon, an important coastal archaeological site in southern Israel that suffers from severe erosion. Based on Pranzini et al. (2018), we analyzed the alternatives, evaluated their cost and efficiency, and assessed their potential environmental impacts. The study concluded that for protecting the southern part of Tel Ashkelon beach, pebble nourishment is the optimal solution, mainly regarding durability and cost. Using this material for nourishment will better absorb the storm wave impact and protect the foot of the archaeological Tel from erosion, and require lower maintenance cost than using finer sand nourishment. Keywords: coastal processes; dredging; nourishment durability; unit sand volume; pebbles; Levant; Tel Ashkelon 1. Introduction The Mediterranean Sea is rich in unique cultural assets and is considered to be the cradle of many civilizations, religions, and cultures [1,2]. Ancient empires and cultures have left a wealth of remains, including coastal settlements, harbors, and anchorages. Some of the most important ancient sites, which represent the mutual relation between man and the sea, are located on the Mediterranean coast of Israel [3–5]. During the 20th century, Israeli ancient coastal sites such as (from south to north) Tel Ashkelon, Yavneh-Yam, Apollonia, Caesarea, Dor, Atlit, and Akko (Acre) (Figure1: top inset), have been severely eroded, mainly due to modern marine construction, as well as sea level rise, and storm waves [1,4,6,7]. If these processes continue, a significant portion of the marine heritage of humanity will disappear, and archaeological and touristic assets of great cultural, scientific and economic value will be lost [1,4]. This coastal erosion may also affect the unique intertidal ecosystems at these sites [8]. J. Mar. Sci. Eng. 2020, 8, 509; doi:10.3390/jmse8070509 www.mdpi.com/journal/jmse J. Mar. Sci. Eng. 2020, 8, x FOR PEER REVIEW 2 of 15 touristicJ. Mar. Sci. assets Eng. 2020 of, 8great, 509 cultural, scientific and economic value will be lost [1,4]. This coastal erosion2 of 15 may also affect the unique intertidal ecosystems at these sites [8]. Figure 1. AshkelonAshkelon coast, coast, the main mari marinene constructions and Tel AshkelonAshkelon site (Photo: Google Earth image,image, 2828 JanuaryJanuary 2016) 2016) (EAPC—Eilat-Ashkelon (EAPC—Eilat-Ashkelon Pipeline Pipeline Company); Company); The The Mediterranean Mediterranean coast coast of Israel of Israeland its and main its ancientmain ancient coastal coastal sites (top sites left (top inset); left The inset); Nile The littoral Nile cell littoral longshore cell longshore sand transport sand transport direction direction(black arrows), (black fromarrows), the Nilefrom Delta the Nile to Haifa Delta Bay to Haifa (bottom Bay right (bottom inset). right inset). One of the most important archaeological sites sites on the Israeli coast is Tel Ashkelon (ancient Ashkelon) [9–11], [9–11], situated within the Ashkelon Nati Nationalonal Park, adjacent to to the southern part of the modern city of Ashkelon (Figures 11 andand2 2).). TheThe mostmost prominentprominent ruins ruins seen seen today today in in Tel Tel Ashkelon Ashkelon are are the Crusader fortificationsfortifications (638-1187 (638-1187 CE) CE) [12 [12–14].–14]. These These remains remains include include several several sections sections of the of oldthe cityold citywall wall and and a short a short part part (40 m(40 long) m long) of its of seaside its seaside wall wall (i.e., (i.e., the Columnsthe Columns wall) wall) (Figure (Figure3). The 3). latterThe latter was wasreinforced reinforced by the by Crusaders, the Crusaders, who reused who granite reused columns granite taken columns from taken Roman from/Hellenistic Roman/Hellenistic monumental monumentalstructures [15 structures]. [15]. J. Mar. Sci. Eng. 2020, 8, 509 3 of 15 J.J. Mar.Mar. Sci.Sci. Eng.Eng. 2020,, 8,, xx FORFOR PEERPEER REVIEWREVIEW 33 ofof 1515 Figure 2.2. TelTel Ashkelon Ashkelon and and its its coast, coast, showing showing the erodedthe eroded beach beach (0–15 (0–15 m wide) m wide) (between (between the red the arrows) red arrows)at the vicinity at the ofvicinity the Columns of the Co wall,lumnslumns and wall,wall, the and widerand thethe (30–50 widerwider m) (30–50(30–50 sandy m)m) beach sandysandy (between beachbeach (between(between the yellow thethearrows) yellowyellow arrows)at the vicinity at the ofvicinity the bathing of the beachbathing (Photo: beach A(Pho rotatedto: A Googlerotated EarthGoogle image, Earth 28 image, January 28 January 2016). 2016). Figure 3. View to northeast of the eroded beach in southern Tel Ashkelon, at the vicinity of the Figure 3.3. ViewView to to northeast northeast of of the the eroded eroded beach beach in southern in southern Tel Ashkelon, Tel Ashkelon, at the vicinity at the ofvicinity the Columns of the wallColumns (photographed wall (photographed by Dov Zviely, by Dov 19 Zviely, December 19 December 2019). 2019). Because ofof thethe importanceimportance of of the the archaeological archaeological remains remains along along the the coast coast of Telof Tel Ashkelon, Ashkelon, it is it our is ourduty duty to preserve to preserve them them for the for sake the ofsake future of future generations. generations. Several Several plans haveplans been have proposed been proposed in the last in 15the years last by15 governmentalyears by governmental agencies; however,agencies; only however, one project only aimedone project at protecting aimed theat protecting Columns wall the Columnshas been completedwall has been so far. completed The Columns so far.far.wall TheThe wasColumnsColumns protected wallwall bywaswas building protectedprotected a ‘sacrificial’ byby buildingbuilding layer aa ‘sacrificial’‘sacrificial’ of stones (3layer m highof stones and (3 1 m m thick)high and on its1 m seaward thick) on side. its se Theaward project side. was The carried project outwas by carried the Israel out by Antiquities the Israel AuthorityAntiquities in Authority 2005. in 2005. Beach nourishmentnourishment isis one one of of the the commonest commonest ‘soft ‘soft solutions’ solutions’ for for coastal coastal erosion erosion [16– [16–21],21], and and it was it wasfound found more more appropriate appropriate from from environmental environmental and economicaland economical perspectives, perspectives, than than ‘hard ‘hard solutions’, solutions’, such suchas seawalls, as seawalls, revetments, revetments, detached detached breakwaters, breakwaters, and groinsand groins [22]. Studies[22]. Studies have have revealed revealed that athat clear a cleardefinition definition of the aimsof the of aims beach of nourishment beach nourishment and a well-based and a well-based knowledge knowledge of the local of physical the local conditions physical (e.g.,conditions coastal (e.g., morphology, coastal morphology, native sediment native grain sedi size,ment wave grain regime) size, are wave crucial regime) for a successfulare crucial coastal for a protectionsuccessful projectcoastal[ 21protection]. Furthermore, project to [21]. achieve Furthermore, a successful to nourishment,achieve a successful a cost-e ffnourishment,ectiveness approach a cost- effectivenessis needed, together approach with is an needed, analysis oftogether alternative with solutions, an analysis effective of alternative planning andsolutions, monitoring, effective and planningusing compatible and monitoring, sediment and for using nourishment compatib [21le,23 sediment,24]. for nourishment [21,23,24]. The presentpresent studystudy analyzesanalyzes sandsand and and pebble pebble alternatives alternatives for for nourishment nourishment of of the the eroded eroded beach beach in inthe the vicinity vicinity of theof the Columns Columns wall wall in Tel in Ashkelon.Tel Ashkel Theon. The study study evaluates evaluates the costthe andcost eandfficiency efficiency of each of each alternative, examines their potential environmental impacts, and suggests