scholarly journals Vulnerability to watershed erosion and coastal deposition in the tropics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Trevor N. Browning ◽  
Derek E. Sawyer

AbstractOver half of the global population is projected to live in the tropics by 2050. Sustainable land development will be challenged by enhanced sediment erosion and deposition, which can negatively impact water quality and ecosystem services in inland and coastal waterways. Existing erosion assessments treat watersheds and coastal zones separately, but we connect them in a two-part vulnerability index to watershed erosion and coastal deposition at 0.0004° (~ 45 m) resolution throughout the tropics. We use open-source datasets and a simple, GIS-based method geared toward tropical, novice end-users. Part 1 of the index reveals a majority of the tropics is vulnerable to erosion. Vulnerability is highest where there are co-occurrences of earthquakes, steep slopes, and high precipitation such as the Caribbean and Southeast Asia. In Part 2, we assess erosion vulnerability at 4 watersheds and include their coastal systems, which can enhance or diminish vulnerability of the entire system to coastal deposition.

Author(s):  
Satoshi Kiso ◽  
Tomohiro Yasuda ◽  
Nobuhito Mori ◽  
Andrew Kennedy

Boulders made of coral limestone transported shoreward have been observed many times in the tropics and subtropical coastal zones, and are called storm boulders or tsunami boulders. They can become lasting evidence of historical mega-tsunami or super typhoon occurrence during the past hundreds to thousands of years, even if no literature record remains. In recent years, a large number of surveys have been conducted worldwide, and the existence of large boulders has been found in several areas such as the Pacific Ocean, the Caribbean Sea, the Atlantic Ocean, and other regions. Since there is limited observational record of their detailed motion, movement limit, and spatial distribution of transport by gigantic tsunami or storm waves, detailed movement mechanisms are still poorly known. This increases the difficulty of developing a model of boulder transport, and interpreting field observations. These hydrodynamic conditions are also directly related to structural loads of interest to engineers and planners. This study aims to measure transport characteristics of coastal boulders through a series of experiments in a tsunami-wave laboratory flume.


2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Akshaya Beluru Jana ◽  
Arkal Vittal Hegde

The coastal zones are highly resourceful and dynamic. In recent times, increased events of tropical cyclones and the devastating impact of the December 2004 tsunami have brought forth the importance of assessing the vulnerability of the coast to hazard-induced flooding and inundation in coastal areas. This study intends to develop coastal vulnerability index (CVI) for the administrative units, known astalukasof the Karnataka state. Seven physical and geologic risk variables characterizing the vulnerability of the coast, including rate of relative sea level change, historical shoreline change, coastal slope, coastal regional elevation, mean tidal range, and significant wave height derived using conventional and remotely sensed data, along with one socioeconomic parameter “population,” were used in the study. A total of 298 km of shoreline are ranked in the study. It was observed that about 68.65 km of the shoreline is under very high vulnerable category and 79.26 km of shoreline is under high vulnerable category. Of the remaining shoreline, 59.14 km and 91.04 km are of moderate and low vulnerable categories, respectively.


Author(s):  
Michael H. Carr

River channels and valleys have been observed on several planetary bodies in addition to the Earth. Long sinuous valleys on Venus, our Moon and Jupiter's moon Io are clearly formed by lava, and branching valleys on Saturn's moon Titan may be forming today by rivers of methane. But by far the most dissected body in our Solar System apart from the Earth is Mars. Branching valleys that in plan resemble terrestrial river valleys are common throughout the most ancient landscapes preserved on the planet. Accompanying the valleys are the remains of other indicators of erosion and deposition, such as deltas, alluvial fans and lake beds. There is little reason to doubt that water was the erosive agent and that early in Mars' history, climatic conditions were very different from the present cold conditions and such that, at least episodically, water could flow across the surface. In addition to the branching valley networks, there are large flood features, termed outflow channels. These are similar to, but dwarf, the largest terrestrial flood channels. The consensus is that these channels were also cut by water although there are other possibilities. The outflow channels mostly postdate the valley networks, although most are still very ancient. They appear to have formed at a time when surface conditions were similar to those that prevail today. There is evidence that glacial activity has modified some of the water-worn valleys, particularly in the 30–50° latitude belts, and ice may also be implicated in the formation of geologically recent, seemingly water-worn gullies on steep slopes. Mars also has had a long volcanic history, and long, sinuous lava channels similar to those on the Moon and Venus are common on and around the large volcanoes. These will not, however, be discussed further; the emphasis here is on the effects of running water on the evolution of the surface.


Author(s):  
Alejandra Bronfman

Picking up in the early 1920s, this chapter tracks the shift of radio technology from military to commercial uses. It follows linkages among the changing material conditions for Caribbean workers, the radio industry’s search for materials like mica and bakelite, and the generation of new markets. Having placed broadcasting in its ecological and political contexts, the chapter uses the trajectories of two amateur radio operators, John Grinan, a New Yorker/Jamaican son of a plantation owner and a member of the team which produced the first transatlantic wireless signals, and Frank Jones, an American plantation manager in Cuba, famous for his self-promoting shortwave transmissions to recover the world of the tinkerers’ romance with an ether jammed with distant sounds. It traces the creation of audiences and publics for the emerging technology, arguing that radio appealed to listeners not because it shrank distances, but because it underscored them, demarcating the Caribbean as exotic and remote. Ironically, it was the deeper technological connections that would propel the mapping of these imagined boundaries between the “tropics” and “the world.”


Author(s):  
Tempest Anderson ◽  
John Smith Flett

The islands of the Caribbean chain have been occupied by European colonists for several hundred years, yet they cannot even at the present day be said to be thoroughly known or sufficiently explored. Though small, they are for the most part moun­tainous, and present usually a ridge or backbone of high land forming the main axis of each island, with sharp spurs on each side running down to the sea. Cul­tivation is practically confined to the lower grounds, where alone there are goodroads, and the interior is covered with dense tropical forest, the aspect of which varies greatly with the altitude, and through which there are only rough bush paths. The valleys are usually very deep and narrow, and the steep slopes are covered with plantations of arrowroot, limes, cocoa, coffee, banana or plantain, while most of the level alluvial ground in the valley bottoms is given up to the growth of sugar cane. In all the British islands, at any rate, the principal peaks and ridges have been ascended, and the main features of the country are delineated on the Admiralty charts, which are the best, and in fact the only available maps. As regards the coast-lines and the lower grounds generally, they are very accurate; but in theinterior only the more important points, the principal mountain summits and the like, have had their position sufficiently determined. The rest of the country has apparently been sketched in more or less carefully—but many of the details as, for example, the courses of the smaller streams, and the number of their branches, cannot be relied on. The want of a good map on a fairly large scale is a great drawback in geological work, and prevents the structure of the country being laid down with anyapproach to minuteness.


1983 ◽  
Vol 7 ◽  
pp. 116-129 ◽  
Author(s):  
Willard D. Hartman

Sclerosponges secrete a basal crystalline and aspicular skeleton of calcium carbonate, either aragonite or calcite, above which lies a thin layer of living tissue which also secretes siliceous spicules and collagenous fibers. The tripartite skeleton of sclerosponges distinguishes them from all other sponges and also from all other multicellular animals, no one of which has an abundant quantity of two disparate minerals helping to make up its skeleton. The cell types and their organization as well as what little is known about their development indicate that the sclerosponges are related to the demosponges. Sclerosponges are inhabitants of shaded crevices, caves and tunnels on coral reefs in both the Caribbean and Indo-Pacific regions. The range of only one species, Merlia normani Kirkpatrick, extends from the tropics into the warm temperate waters of the Mediterranean Sea.


1978 ◽  
Vol 5 (3) ◽  
pp. 183-190 ◽  
Author(s):  
Anne LaBastille ◽  
Douglas J. Pool

Tropical New World cloud-forest may best be described as the area of persistent cloud contact with tropical mountain vegetation. Cloud-forest exists in at least five life-zones, being characterized, generally speaking, by having high precipitation and humidity, dripping moisture, continuous cloud or mist cover, absence of frost, and trees laden with mosses and epiphytes.


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