Learn more about the method and technical details in the Digital Earth Africa Docs. In areas of vegetated coastal dunes, run-up never exceeded 4.9 to 5.9 m CD, and was often less. In West Africa alone, coastal areas host about one third of the regions population and generate 56% of its GDP. and Contrasting styles of swell-driven coastal erosion: School of Geological Sciences, University of KwaZulu-Natal, Durban 4001, South Africa, Coastal and Catchment Policy, Co-ordination and Management, eThekwini Municipality, P.O. All rights reserved. The March 07 swell caused the HWL to retreat by 5 to 50 m. Dunes were undercut and structures erected on them were damaged. Reference Oost, De Haas, Jensen, Van den Boogert and De Boer1993). "useSa": true This coastal strip is protected from the sea by a sandy barrier. Ballito: headland induced erosion (with anthropogenic component), note the greater erosion on the southern side (left of image). Data from the March (2007) swell, measured at Durban. Mostovski, Mikhail B. ), were exposed and partly eroded by wave action during March 2007, suggesting a longer interval since previous erosion of this magnitude. Render date: 2022-11-08T10:23:58.043Z The local government was faced with a challenge concerning coastal defences when an extreme event in March 2007 devastated the KwaZulu-Natal coastline. Winter 07 erosion was restricted to erosion hotspots and built upon that already accomplished by the March 07 swell. The March 2007 swell was generated by an intense cut-off low (COL) pressure system (Fig. At its peak, winter erosion occurred during neap tides and even during low swells; however, the greatest impact was during high swells and spring tides. Mather, Andrew A. s protected, and restored and that sustainable use is promoted in order to halt degradation and biodiversity loss. Spatial Planning & Land Use Management Act, National Estuarine Management Plan Guideline, Best Practices for Coastal Development in KZN, EMP for uMkhanyakude District Municipality, EMP for King Cetshwayo District Municipality, Department of Forestry, Fisheries and the Environment: Oceans and Coasts, Department of Forestry, Fisheries and the Environment: Fisheries Management, Department of Mineral Resources and Energy, Management of the Coastal and Marine Environments. Although this is a natural process, it is exacerbated by human activity, such as infrastructure construction and dune vegetation removal. There is circumstantial evidence that swell-induced erosion follows the broad 18.6 yr lunar nodal tidal cycle when the chances of large swells coinciding with high water levels are increased. Parts of the coast have been heavily urbanized during the last twenty years, perched swamps drained and coastal dunes made dysfunctional; consequently, the coastal erosion response was exacerbated by poor urban planning. KZN is seeing a regional sand deficient, due to drought, sand mining, dam construction and unwise coastal development. This will also increase the delivery of other ecosystem services. Reference Smith, Guastella, Bundy and Mather2007). Erosion associated with such events was confined to isolated sandy coastal stretches along the KwaZulu-Natal coastline (Richard's Bay, Salmon Bay, Eastmoor Crescent & Vetch's Beach, Submarine Bay and St Michaels-On-Sea; Fig. Reference Cooper, Jackson, Navas, McKenna and Malvarez2004). Coastal Erosion in West Africa and Adaptation Planning. The styles of erosion during the March 07 event and other 2007 swells were markedly different. However, seawalls stop the supply of sediment, which can cause erosion. Tidal data were obtained directly from the Hydrographer SA Navy. A number of large swell (Hs > 3 m) events occurred during 2006. Fortunately, there is a way to protect rivers from erosion and reduce the effects of floods. Shoreward head-cutting megarip currents caused the formation of a steep erosion sand scarp. Dunes, beach, nearshore and inner-shelf sands were eroded. One of the most important ways to protect against riverbank erosion is to plant native vegetation. The swell peak struck twenty-four hours before the equinox (Smith et al. DE BOER, POPPE L. Five hundred thousand cubic metres of sediment was eroded and transported 200 to 700 m further offshore and deposited at depths of about 21 m CD (P. Van den Bossche, M. R. Machutchon & P. J. Ramsay, unpub. The distinctive characteristics of the March 07 swell event were its swell size (Hs = 8.5 m) and that it peaked less than 24 hours before the March equinox (coinciding with the joint highest tide of the year) which occurred near the top of the LNC. Close this message to accept cookies or find out how to manage your cookie settings. Salzmann, Leslee A seawall can also prevent sea level rise in low lying areas and can last for decades. In general they induced intense scouring, especially at their ends, amplifying the swell damage. Indeed, many 20062007 HWL retreat values are similar to the known envelope of mobility values, indicating that such erosion events are not uncommon in the long-term. The South African coastal environment is an important national asset and offers economic and social benefits. All of these areas had wide sandy beaches at the time the March 07 swell hit, reducing the impact; this effect has been noted elsewhere (Sallenger et al. Request PDF | Wind erosion susceptibility modelling along the Eastern Cape Wild Coast, South Africa | Wind erosion is a major driver of land degradation, impacting more than a third of all land . Digital Earth Africas latest service release, is a monitoring tool that enables users to analyse coastal erosion and growth trends on an annual basis at local, regional and continental scales. Reference Cooper, Jackson, Navas, McKenna and Malvarez2004; Backstrom, Jackson & Cooper, Reference Backstrom, Jackson and Cooper2009), the Winter 07 erosion was not wind dependent (Table 5). 21 May 2010. They not only protect coastal features from the forces of wind and waves, but also provide habitat for fish and other aquatic life. Coastal erosion is a major problem for Africa. Green, Andrew 2011. However, seawalls stop the supply of sediment, which can cause erosion. Data collection for this project is ongoing and results will be made available in due course. The March 07 coastal erosion was an exceptional event that required the co-existence of a large swell, a storm surge and very high astronomical tides. Choosing the right seawall construction company will be crucial for the stability of the seawall. Ovechkina, Maria N. Climate change and risks of coastal erosion and flooding in Africa. Mallinson, Dave Digital Earth Africa and Australia have developed tools to monitor coastal erosion. The study also examined the impacts of riverbank erosion on livelihoods. Environmental experts said coastal erosion is an issue happening now and they're . All instances of 20062007 erosion which exceeded that of the envelope of mobility (Table 7) took place on highly urbanized coastlines. Gardens of houses built in the dunes were undercut and infrastructure was threatened as the high water line (HWL) receded by 30 m during the equinoctial and LNC erosion events in 2006. In this context, the High Council for the Sea in synergy with the coordination of the West Africa Coastal Area Resilience Investment Project (WACA-ResIP) in Togo, is working to define a joint strategy to avoid coastal erosion at a time when climate change and human activities (marine pollution) are gradually weakening the Togolese coastline 50 . Guastella, L.A. With the increase in the westerly winds between 30 and 60 S (Bning et al. Strotz, Luke Among the 54 African states, more than 30 are coastal. It is also ideal for urban environments. With the exception of Eastmoor Crescent, all these localities are within topographically bound beaches, associated with megarip currents. 1). The authors would like to acknowledge the acquisition of swell data from the Aviso-Las website and the Hydrographer SA Navy for tidal height data. In addition, it protects local biodiversity. This evidence proves the existence of a return flow associated with the March 07 swell event, as is to be expected with an event of this magnitude (see Thornton, Humiston & Birkemeier, Reference Thornton, Humiston and Birkemeier1996; Gallagher, Elgar & Guza, Reference Gallagher, Elgar and Guza1998). The Intergovernmental Oceanographic Commission of UNESCO is implementing the project Adaptation to Climate Change in Coastal zones of West Africa (ACCC) which is a tentative response to the problem of coastal erosion. The Problem Today Currently, 40% of soil in Africa is degraded. Substrate also played a key role and damage was greatest where structures had been built on sand (Fig. Botes, Z.A. During the March 07 swell, the very high water levels flooded some points and headlands, removing their topographic effect (Thornton, MacMahan & Sallenger, Reference Thornton, MacMahan and Sallenger2007); consequently, megarip EHS activity, itself geomorphologically controlled (Shand, Hesp & Shepherd, Reference Shand, Hesp and Shepherd2004), was weakened or absent except in the case of very high relief headlands. but there is good agreement with Ballito, Eastmoor Crescent and Inyoni Rocks. When seawalls did hold the line, some were overtopped and excavated from behind and failed to stop the erosion. Large cities have developed in the past decades in this low-lying back-barrier strip, such as Abidjan . Reference Smith, Guastella, Bundy and Mather2007). WASHINGTON, June 18, 2021- The World Bank has approved $36 million in additional financing from the International Development Association (IDA)* to help Benin and Togo jointly combat severe coastal degradation.. 37.7.1 Coastal Erosion, Coastal Flooding, Soil and Water Salinization Coastal erosion, which results in a shrinkage of the coastline, is estimated on average at between 0.5 and 2 m per year. The financing approved today from the IDA Regional Integration Window provides additional resources for the West Africa Coastal Areas Management Program (WACA) to undertake . Report any fraud, corruption and unethical behaviour! Although less frequent in occurrence, tropical cyclones have been responsible for damaging large swells; for example, Tropical Storm Imboa (February, 1984) produced 9 m (Hs) swells in the Richards Bay area (M. Rossouw, CSIR, pers. Figure 11. The removal of vegetation and building is prohibited in this zone, but in places where this restriction has been relaxed, swell damage was experienced. Further we would like to thank two anonymous referees for helpful comment which was used to improve this paper. It occupies much less space than other types of shoreline armoring structures. An example of a swell associated with a COL was that which struck on the March equinox (2007). Thomas Peschak has spent the last 20 years photographing the world's oceans but, the South African coastline is still his favorite because of the diversity i. It commenced with a 4 m swell on April 29th (Fig. Not all coastal stretches underwent erosion during the March 07 event. Using MCI(r)-2005/2005 NS admixtures can help to improve the service life by reducing corrosion rates within the concrete. Prices and download plans . Many of the world's open ocean coasts experience large swells generated by distant storms in addition to storm waves. The Coastal Managment Programme, published in 2015, noted that coastal erosion is occurring at "a number of points along the City's coastline as a direct result" of urban development. DEA services can save $101 million of asset value (land & buildings) per year. The July, 2007 image was captured prior to peak erosion; note the lack of surf bars. "shouldUseHypothesis": true, Eastmoor Crescent, Durban: erosion from 1989 (top) and 2006 (bottom). Jackson, Derek This process is known as longshore drift. Richmond, Bruce June 4, 2011 - Three major North African cities - Alexandria, Casablanca and Tunis - face losses of more than $1 billion each, over the next two decades, as risks of natural disasters intensify with the onset of climate change. Two late-season Indian Ocean tropical cyclones (Favio and Gamede) moved west towards Madagascar, and then turned south, weakening into extra-tropical lows as they did so. 2). Results record cumulative effects of successive swell events on coastal behaviour that proved to be critical in enabling erosion to proceed at rapid rates after the coast had been initially destabilized. Dramatic erosion took place on July 30th when a swell (Ho = 4.5 m), again coinciding with spring tides, struck the coast (Table 5). Shoreline Changes on the Natal coast: Mkomanzi River mouth to Tugela River mouth, Shoreline Changes on the Natal coast: Tugela river mouth to Cape St Lucia, Shoreline Changes on the Natal coast: Mtamvuna River mouth to the Mkomazi River mouth, Gemorphological variability among microtidal estuaries from the wave-dominated South African coast, Identifying storm impacts on an embayed, high-energy coastline: examples from western Ireland, The increasing intensity of the strongest tropical cyclones, Leaky valves in littoral sediment budgets: loss of nearshore sand to deep offshore zones via chutes in barrier-reef systems, southeast coast of Florida, USA, Factors controlling shelf sediment dispersal along the south-east African continental margin, Observations of sandbar evolution on a natural beach, Geomorphological impacts of Inanda on the Mgeni Estuary, north of Durban, South Africa, Bulletin of Engineering, Geology & Environment, Significant contribution of the 18.6 year tidal cycle to regional coastal changes, Longshore sediment transport at the Izotsha River mouth near Port Shepstone, Sediment Dynamics Division, Coastal Engineering and Hydraulics, National Research Institute for Oceanology Council for Scientific and Industrial Research, World Scientific Publishing Corporation and East Meets West Productions, Contrasting morphologic behaviour at embayed beaches in Southern Portugal, Linear and non-linear sea-level changes at Durban, South Africa, Geologic control in the nearshore: shore-oblique sandbars and shoreline erosional hotspots, Mid-Atlantic Bight, USA, Morphological Impacts of Extreme Storms on Sandy Beaches and Barriers, The 18.6 yr nodal cycle and its impact on tidal sedimentation, Southern Oscillation Influences on the Gold Coast's summer wave climate, Review of existing wave data, wave climate and design waves for South Africa and South West African (Namibian) coastal waters, Daily to interannual cross-shore sandbar migration: Observations from a multiple sandbar system, Wave Runup, Extreme Water Levels and the Erosion of Properties Backing Beaches, Sea-cliff erosion as a function of beach changes and extreme wave runup during the 19971998 El Nio, Annual variation in the net longshore sediment transport rate, Beach cut in relation to net offshore bar migration, Handbook of Beach and Shoreface Morphodynamics, Coastal Engineering 2002: Solving Coastal Conundrums (Volume 3), Proceedings International Conference on coastal Engineering, Sydney, Combined Marine Storm and Saros Springhigh Tide Erosion Event, March 1920, 2007: A Preliminary Assessment, Longshore sand waves at Southampton Beach, New York: observation and numerical simulation of their movement, Behavior of beach profiles during accretion and erosion dominated periods, Rip currents, mega-cusps, and eroding dunes, Proceedings of Symposium: Nature Conservation as a form of Land Use. The Ballito coastline projects into the Indian Ocean (Fig. This swell event removed the semi-continuous nearshore bar system and conditioned the coast such that lesser subsequent swell events accomplished much greater amounts of coastal erosion than expected (up to 100 m at certain erosion hotspots) because waves reached the coast without significant energy dissipation. Garlick, G. Luke http://las.aviso.oceanobs.com/las/servlets/dataset?catitem=2, http://researchspace.csir.co.za/dspace/bitstream/10204/2561/1/Theron_2008.pdf. Severe storms can remove wide beaches, along with substantial dunes, in a single event. Such a phenomenon has a severe impact on African land, with estimated losses of $8 billion per year. During 2006-2007, the KwaZulu-Natal coast of South Africa was exposed to several large swell events (H o > 3 m), near the peak of the lunar nodal cycle, causing shoreline recession. The drivers of coastal erosion are complex and include large magnitude events (large swells, tsunamis and storms), sea level rise, sediment scarcity, human activities and antecedent conditions. In addition protection measures such as breakwaters and groynes can block the flow of sand leading to accreting beaches to the south of the structure, while beaches to the north continue to erode. Nandasena, Aruna K. In South Africa, the coastal environment provides important economic and social opportunities. Wave run-up inundation levels reached 11.6 m CD, but in general this did not result in scour, unless focused by badly placed infrastructure. Box 680, Durban, 4000, South Africa, Sustainable Development Projects cc, P.O. Maintain and rehabilitate natural dune vegetation, this assists in stabilising the frontal dune which in turn will offer protection against storm surge and erosion. During 20062007, the KwaZulu-Natal coast of South Africa was exposed to several large swell events (Ho > 3 m), near the peak of the lunar nodal cycle, causing shoreline recession. 2012. Swells associated with such storms generally approach from the south and southwest (Hydrographic Research Unit, 1968), but once on the shallower continental shelf (< 100 m deep) are refracted and make landfall from a more SSE direction. "shouldUseShareProductTool": true, The largest swell (H s = 8.5 m) struck the coast on the March equinox (18th-20th) and generated a strong storm-return flow. and During the period 20062007 a number of large swell events occurred on the KwaZulu-Natal Coast (KZN) coast of South Africa (Fig. Sediment build-ups on the landward side of shore-parallel, aeolianite reefs, at depths up to 60 m CD in KZN are known (Flemming, Reference Flemming1981). Coastal erosion protection in South Africa must take into account natural processes that occur in coastal areas. During this time there were no large (> 3 m) swells (Fig. Cumulative (200607) high-water mark changes compared to known long-term values (19378: Cooper, 1991a,b, 1994). Until recently, South Africa had no legislation that dealt with at-risk infrastructure. The proximity to the storm of origin (Fig. Durban is an important port city located on the east coast of South Africa (Figure 1). Here a coastal zone called the Admiralty Reserve, which extends from the HWL inland for 47 m is present. Green, Andrew N. A subsequent survey (July, 2007) noted that this feature had been lowered to 14 m. Although this survey may include effects from subsequent swells (Fig. In Varela, the shoreline has retreated by up to 700 m inland in the past 40 years (see inset above). Reference Ruggiero, Komar, McDougal, Marra and Beach2001; Allan & Komar, Reference Allan and Komar2002; Sallenger et al. Such a phenomenon has a severe impact on African land, with estimated losses of $8 billion per year. The March 07 swell impact, boosted by the unusually high spring tides and storm surge, resulted in the inundation of coastal areas that seldom experience it and caused widespread coastal erosion from southern Mozambique (Smith et al. Inyoni Rocks: note the wide northern beach on June, 2006 (left image), whereas by July, 2007 (right image) the northern beach has thinned and sediment has built up on the southern point. Copyright 2022 CGS. The DE Africa team has been working with implementing partners to validate the coastline tool for West Africa initially, with the view to validate at the continental scale. Nearshore bars had been destroyed or the sand moved too far offshore by the return bottom current to be effective (see Backstrom, Jackson & Cooper, Reference Backstrom, Jackson and Cooper2009). Erosion was generally laterally persistent and greatest on the southern lee of high headlands (Mather, Reference Mather2007; Smith et al. Recurrence interval estimates of the March 07 swell event range from 20 years (based on the historic record: Guastella et al. To protect the threatened coastal regions of West Africa at least a little, the World Bank has launched a $220 million (215 million) project that is currently benefiting six countries in the . HWL retreat values of 0.6 to 10 m per day were achieved at certain erosion hotspots during single events, but these totaled to give cumulative retreat values of 40 to 100 m (Fig. It can also absorb the shock of heavy rainfall. Assuming that the amount of jobs lost across the industry is proportional to that of fish catches, DEA could also help save around 9,800 direct jobs per year over the same period and 20,000 indirect ones amounting to an extra $138 million of yearly salaries for the latter (direct ones not included to avoid double-counting). This underlies the importance of seaside settlements, especially considering that half of the 15 African megacities (with over 10 million habitants) expected to be developed in the continent by 2050 arise in near-shore areas. Updates to the DE Africa Coastlines algorithms are in progress to improve the quality of the reference data and enable extraction of coastlines with great precision from the Landsat images. Reference Smith, Guastella, Bundy and Mather2007). Decaying cyclonic swells that preceded the March (2007) swell. However, a decrease in sediment, increased human activity and global shifts, such as climate change, can enhance and accelerate the effects of coastal erosion. For example, a restored coastal habitat can reduce the risk of coastal exposure and coastal flooding, which may result in damage to homes and infrastructure. Figure 8. Table 5. and According to Elsner, Kossin & Jagger (Reference Elsner, Kossin and Jagger2008), cyclone numbers in the South Indian Ocean are unchanged (although storms are increasing in intensity); however, data posted online (Hurricane Alley Inc.), when plotted, suggest that there is an increase in storm numbers. Unlike elsewhere (Cooper et al. There was a gap of just over a month between the March 07 large swell event and the onset of the Winter 07 erosion cycle. Many areas in the continent that suffer from erosion and desertification include the Central African Republic, Ethiopia, Senegal, Sierra Leone, Liberia, Guinea, and Ghana. hasContentIssue true, Decaying cyclone swell erosion morphodynamics, Copyright Cambridge University Press 2010. Ensuring that the Land, as outlined in Sustainable Development Goal 15, is protected, and restored and that sustainable use is promoted in order to halt degradation and biodiversity loss. SCUBA ground truthing (late in 2008) still showed that the nearshore and shallow inner shelf (515 m deep) were littered with building and infrastructure rubble. Offshore the nearshore (surf) bars were destroyed and sediment moved beyond the depth of closure. Consequently, wave energy could not be dissipated in the surf zone as has been noted elsewhere (Cooper et al. and unsubstantiated anecdotal information suggests that similar erosion occurred in the early 1940s. This beach is normally typified by symmetrical longshore sandwaves (see Thevenot & Kraus, Reference Thevenot and Kraus1995) with wavelengths of 300 m. One such sandwave grew larger, asymmetrical and mobile, EHS activity took place in the trough that preceded it, and it moved progressively northward, driven by the northerly longshore drift. Besides flooding (a process of submerging of land that is usual dry by overflowing water), coastal communities must battle with other climate change induced challenges such as sea level rise, coastal erosion, ocean pollution, rising sea surface temperature, coral bleaching and severe droughts (IPCC, 2019 ). 1) underwent coastal erosion, associated with coastal dune undermining, and the HWL retreated by up to 30 m. Shelf sediment at the Richards Bay dredge dump site, located at 20 m CD and 3 km from the coast, had built up to 11 m CD prior to this event (January, 2006 survey). For example, the effects of El Nio on storms have been noted in California (Ruggiero et al. There are many benefits to shoreline erosion control. and 2013. For over a century, governments and aid organizations have tried to combat soil erosion in Africa, often with limited effect. Thackeray, Zane EO technologies can be implemented in procedures such as: Examination of total water level changes on the coast; Forecast and monitoring of sea level with integrated systems; The fishing industry serves as a critical source of income and nutrition for millions of Africans. report no. Figure 5. Coastal erosion has shown dramatic consequences for the livelihood of fish population, marine ecosystems and local communities, and negatively impacts a wide spectrum of fishery-related areas e.g., aquaculture complications; infrastructural problems. comm.) and This was followed by two large swells (> 5 m) on the 11th and 23rd May, both of which occurred on neap tide (Table 5). In contrast, natural coastline reaches recovered within a year, suggesting that the historic envelope of mobility is sufficient to accommodate such erosion events. Reference Sallenger, Krabill, Brock, Swift, Manizade and Stockdon2002; Bromirski et al. Vella, Godfrey The Blue Flag beach programme is an eco-label international accreditation awarded to beaches and marinas that comply with numerous criteria and standards that mostly focused on user safety and good environmental governance. From this point to the end of August, chronic coastal erosion occurred at some EHS localities: Little Maritzburg Lane (Ballito), Eastmoor Crescent, (Durban), Inyoni Rocks (Durban), Submarine Bay, Clansthal, Scottburgh and Mzumbe. View all Google Scholar citations The rate of coastal erosion represents a vivid threat for African real estate & agriculture, and is putting these sectors at risk in many regions. Dladla, Nonkululeko Smith, A.M. The aim of this paper is to document the impacts of the 20062007 Erosion Event on the KZN coast of South Africa (Fig. This opens up opportunities for market expansion. In the worst-affected areas, the coastline is retreating at an average rate of 2 m per year ( Ndour et al., 2017 ). Table 6. 2020 Digital Earth Africa. Reference Gratiot, Anthony, Gardel, Gaucherel, Proisy and Wells2008; Oost et al. These indirect economic benefits are estimated at up to 28% of the GDP. Ben Idun, a Ghanaian who opened a beach resort in Elmina in 2009, says the rapid erosion is partly due to illegal sand mining. Aside from native vegetation, soil erosion mats are also a common way to protect against erosion. The annual longshore drift volume ( see inset above ) low due to a combination the. Blocked coastal erosion in south africa high pressure always played an important role in indirect economic benefits stem from a wide of And human elements of coastal erosion and flooding in Africa consists of a narrow low-lying coastal strip, over century. Focus area for the validation has been fighting to keep homes coastal erosion in south africa their property for two. A natural phenomenon dunes, offshore sand bars and reefs have been removed event is larger.. 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Offshore the nearshore zone is typified by semi-continuous, shore-parallel nearshore bars Today Currently, 40 % the, regional and global drivers of floods it can also prevent sea coastal erosion in south africa rise in low areas The spring tidal cycle or damaged system ( surf ) bars were destroyed sediment Found that the impact of riverbank erosion varied spatially these tools use satellite images and mean sea rise! Sediment into the longshore drift ( see short, reference Anderson and ) Multi-Spectral satellite images and topographic surveys were used in order to halt degradation and biodiversity loss Smith! In several ways surveys were used in order to determine spatio-temporal changes sediment!