Shoreline sensitivity to oil spills, the Mediterranean coast of Israel: Assessment and analysis
Abstract This study, which was carried out during 1999–2002, deals with the identification of the environmental sensitivity of the Mediterranean coastline of Israel to marine oil spills. It includes GIS sensitivity mapping and an analysis of the environmental vulnerability of Israel's shoreline resources. The study analyses the main sources of risk for maritime accidents in the southeastern Mediterranean and develops scenarios for possible oil spills incidents, including an analysis of the priorities for protection of the various coastal ecosystems, in an event of a large spill. It describes the morphology of the coastline of Israel, as well as the main hydrographic and meteorological patterns that dominate and control the dynamics of the shorelines, and of potential major oil spills. The study also discusses the different ways in which oil spills may affect natural ecosystems and socio-economic resources along the coastline of Israel. The basic research question of the study was how different geomorphic and land-use types of the Mediterranean shoreline would be affected by large quantities of spilled oil washing ashore from the sea. The study aims at determining the relative sensitivity of different types of shoreline and ‘prioritizing’ the different types of shoreline and coastal resources to be protected following a large oil spill. The study also aims at presenting the data collected and analyzed to both the scientific and environmental communities, and to the operational national authorities responsible for oil spill preparedness and response, in a clear and useful way. One of the main conclusions of the study is that generally, the sensitivity of the Israeli Mediterranean coastline to oil spills could be considered moderate, compared with other fragile ecosystems. This is mainly because of the morphology of the sandy beaches and the high exposure of most types of beaches to energetic natural cleanup processes. Still, along the southeastern Mediterranean coastline there are ecosystems, habitats, shoreline types and coastal resources that are sensitive to oil spills.
Sediment transport model of the southeastern Mediterranean coast
Abstract The relationship between: (a) the gradual change of the shoreline orientation in the southeastern Mediterranean from east—west to north—south, (b) the longest fetch direction of the Mediterranean (east—west), and (c) the dominant source of sediments being the Nile Delta to the west, provides a unique opportunity for construction of a model of the longshore sediment transport patterns. The input for this model consisted of: (a) two depth grids totaling 33,795 depths, and (b) nine selected wave conditions. The nine selected wave conditions were based on an analysis of the existing wave observer data, fetch considerations and storm records. The input conditions were waves from the northwest and west with wave periods of 5, 9 and 11 sec, southwest waves of limited fetch with wave periods of 5 and 9 sec, and 13-sec waves from 282.5° azimuth, potentially the largest fetch (2,400 km) direction. The 13-sec waves are both the longest waves theoretically possible and also the longest waves observed. The results show that the rate of longshore transport is larger for short-period (5 sec) than for long-period (9, 11 sec) waves, for all wave approach directions, given the same input wave heights. This is because of the larger shoreline angles of the short-period waves, due to lesser wave refraction. The results of these computations also illustrate the presence of four distinct zones of longshore sediment transport (from southwest to northeast): 1. (1) Western Zone (El Arish to Rafah), where all wave approach directions cause transport to the northeast, and therefore net transport equals gross transport. 2. (2) Central Zone (Rafah to Haifa), which is characterized by converging longshore transport nodal points that shift along the coast in response to changes in wave direction and to a lesser extent, wave period (i.e., north of the nodal point longshore transport is directed to the south, and south of the nodal point transport is directed to the north). For waves from 282.5°, the nodal point is at Netanya and for 315° at Rafah, the southern border of the central zone. 3. (3) Haifa Bay, a 20-km shoreline segment having significantly lower wave energy than the other coastal zones for all wave conditions except 5-sec waves from the northwest which cause southern transport. Even for southwest 9-sec waves, the sediment transport in this area is essentially zero due to wave refraction, and this area may be considered a sediment sink. 4. (4) Northern Zone (Akko to Rosh Haniqra) which is subject to intense wave refraction over the nearshore Akhziv Canyon, resulting in great variably of local longshore transport for most wave conditions. This model of longshore sediment transport of the southeastern Mediterranean coast explains many observed shoreline phenomena. For example, the lack of quartz sediment north of Akko, derived from the Nile River and Kurkar cliffs to the south, appears to be due to Haifa Bay which acts as a sediment sink for northward moving sand. The large differences in sediment transport between the Bardawil Lagoon (Western Zone) and Gaza (Central Zone), as evidenced by the differing sand accumulations on the southern sides of coastal constructions in these two zones, is attributed to the increasing importance of waves from the northwest in causing southwestern transport along the coast northeast of Rafah. The lack of strong indicators of transport direction (such as sediment accumulations differentially on one side of the structures) along the coast of Tel-Aviv and to the north is due to the continuously changing directions of longshore transport with changing wave conditions in the Central Zone, and to intense refraction in the Northern Zone.
An Internet-based Real-time Heavy Rainfall Display System
A new storm warning system, which can be accessed through the Internet and by cellular phones is described. At the time of a heavy rainfall for disaster prevention, it is important that every resident understand how heavy is that rainfall. A real-time heavy rainfall display system designed for all of Japan provides such information (http://www.disaster-i.net/rain/). In that system values for 1-hour precipitation, 24-hour accumulated precipitation, etc. are displayed at every observatory. Advantages are that not only the latest observations but differences from the historical highest records can be seen. Almost all information is displayed by characters so that users have easy access to the system even when the communication network is crowded. Access date for the six months after the system opened shows that the average daily number of accesses of the top page was 306, and the largest number 3078. The maximum number for daily access to all the pages was about 21,500. This is about 2% of the number obtained on the same day for a similar system operated by the Ministry of Land, Infrastructure and Transport (http://www.river.go.jp/).