Rekonstrukcija recentnih morfoloških promjena žala uz pomoć metode ponovljene fotografije – primjer žala Zogon na otoku Hvaru (Srednji Jadran)

Abstract

U radu je analiziran geomorfološki sustav koji čine jaruga i žalo Zogon na otoku Hvaru s ciljem diferenciranja prirodnih i antropogenih procesa koji utječu na promjene žala. Primjenom metoda ponovljene fotografije, orto-foto snimaka i terenskog kartiranja ustanovljeno je da se u razdoblju od 60-ih godina 20. stoljeća do danas površina žala Zogon smanjila za oko 50 %. Smanjenje žala može se povezati s recentnim antropogenim djelatnostima na širem području istraživanja, osobito višestrukim nasipavanjem korita jaruge prilikom gradnje te manjim promjenama u korištenju zemljišta i prirodnom regeneracijom vegetacije što uzrokuje smanjenje dohrane žala. S druge strane, preokret u evoluciji žala u promatranom razdoblju, koje je po definiciji akumulacijski reljefni oblik, iz akumulacijskog ili stanja ravnoteže u stanje dominantne erozije možemo povezati s recentnim klimatskim promjenama i izdizanjem relativne morske razine. KLJUČNE RIJEČI: žalo, jaruga, obalna geomorfologija, promjene zemljišnog pokrova, promjene korištenja zemljišta, klimatske promjene, vinogradarstvo, Sveta NedjeljaThe geomorphological system composed of a torrent and a beach on the Island of Hvar was analysed with the aim to define natural and anthropogenic processes which influence changes in beach morphology. Using repeat photography method, ortho-photo images and field mapping it was found that between the 60s of the last century and the present, the Zogon beach reduced in size by approximately 50%. The reduction of the beach size can be related to the recent anthropological activities in the wider study area particularly due to multiply filling of the torrent bed during construction works and minor land use changes, as well as due to natural reforestation which all cause a decrease in the supply of material to the beach. On the other hand, the reversal of the beach evolution in the observed period, which is, by definition the accumulative relief form, from the accumulative state or state of balance, to dominant erosion, can be associated with recent climate change and relative sea level rise. 166 UVODRecentne klimatske promjene veliki su problem današnjice te su stoga i česta istraživačka tema. Najbolje se uočavaju na područjima koje čovjek dobro poznaje ili na područjima za koja postoje vizualni zapisi iz prijašnjih godina kao što su fotografije, videosnimke, slike krajolika i sl. Brojne promjene vidljive su danas duž istočne obale Jadrana npr.: otapanje leda u planinskim speleološ-kim objektima (Ledenica u Štirovači) (Boi i dr., 2012.), podizanje razine mora (Faivre i dr., 2013.; Faivre, Butorac, u tisku), poplave kao posljedica oborinskih ekstrema (Abdulaj i dr., 2014.; Gaji-Čapka, Cindri, 2014.) učestala jaruženja (Faivre i dr., 2011.), česta olujna nevremena i olujni uspori (Meugorac i dr., 2015), aktiviranje klizišta (Faivre i dr., .; Mihali i dr., 2017.) i mnoge druge.Promjene se najprije i najlakše mogu primijetiti duž obale, gdje se kopneni i marinski okoliši isprepleću. Stoga su obale danas ključna geografska područja, jer lež...

Assessment of Remote Sensing Techniques Applicability for Beach Morphology Mapping: A Case Study of Hvar Island, Central Adriatic, Croatia

“…In addition, multispectral features are often used to study hazards, e.g., floods [30], or forest fires, e.g., as in Reference [31]. Furthermore, reforestation, which usually occurs after deagrarization, thus, could have an impact on reducing gullying processes influencing beach erosion [32,33].…”

“…Beach surveys and techniques can be direct or indirect [41]. Direct methods and techniques refer to in situ measurements using GNSS or topographic measurements [32,33,42] and indirect referring to remote sensing data from satellites and aerial photographs [43,44]. Prior to remote sensing capabilities, a standard technique in beach surveys related to terrain profiling and evolved through echo sounders [45].…”

“…The number of beach surveys along the Croatian Eastern Adriatic Coast has increased in the last decade. Accordingly, a research methodology is being developed from surveys being conducted by direct in situ measurements in the field, using GNSS receivers, handheld cameras, and usually in combination with other methods (e.g., repeat photography) [32,33,42,62], towards the use of photogrammetric SfM methods by means of a handheld camera that provide creation of high-resolution models [63,64]. Recent studies use UAV for data collection, whose images are also processed with photogrammetric techniques and result in very high-resolution models [61,65].…”

“…Today, they are also under increasing anthropogenic pressure. These activities reinforce natural changes, such as erosion, so that beach replenishment is very often required [33,66].…”