La necesidad y viabilidad de la reglamentación de las reservas forestales

The following vessel and barge combination was chosen as a reference case for risk modeling and as baseline for risk analysis from which generalizations may be made to other segments of the fleet:

Barge for oil: L 180ft (55m), W 52ft (15m), D 14.5ft (4.4m); 2,400 DWT LT, 1100 GRT with 12,000 bbl. capacity trading between Anchorage, Kotzebue and Kaktovik, Alaska. Push tug with engines rated at 1,350 HP total.

Vessels of this type provide home heating and diesel oil supplies to rural Alaska communities along the western and northern coasts in the spring and autumn each year (NSREP 2015). Supplies are transferred to shallow draft literage barges for local delivery.

Although the area nearby the city of Anchorage is well surveyed and charted, the areas to the north along the west coast and further around and to the east along the northern slope of Alaska are poorly surveyed, if at all, and navigation charts are poor. Proceeding north to Kotzebue only the five mile channel from clear water to the harbor is surveyed with adjacent waters shown in blue without soundings in figure 5.6. Aids to navigation are not charted at all, and are subject to being moved based upon constantly changing bottom conditions. A portion of the route between Kotzebue and Kaktovik is shown in figure 5.6a where spot and track line soundings predominate except directly

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along the shoreline. Such navigation chart coverage is common along the entire route. The immediate area around Kaktovik and the harbor shown in figure 5.6b is well charted, however most soundings disappear after leaving the shoreline.

(a) Channel to Kotzebue Harbor, AK (NOAA Chart 16161)

(b) Kaktovik, AK (NOAA Chart 16043)

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Risk assessment using existing technology – A process for risk assessment using

present technology is shown in table 4. Assessment of hydrography is made based upon the recency of survey and the coverage of the survey along the route. Where hydrographic surveys have recently been performed and absent significant storm activity, is it likely that the surveyed bottom configuration still accurately represents the present bottom configuration. As the time since the last survey becomes greater the probability of changes in the bottom increases. However, when surveys are more than 30 years old another factor comes into play in terms of the lower resolution of older sensors and technologies used to perform the survey. Multibeam sonars that provide full bottom coverage at high resolution have only come into use since the 1990’s (NOS, HHS). Prior to that single-beam echo sounders were used from the 1940’s to the 1980’s. Earlier technologies included the wire drag survey introduced in 1904 and the leaded line survey before then.

Coverage of survey refers to comprehensiveness in the area along the route of transit. Full bottom coverage with soundings, depth contours and other topography and hydrography features are given a lower risk factor than areas where only partial full bottom exists in some areas and is absent in others. Likewise, track and spot soundings and lack of depth contours and other features warrant a higher risk factor. A navigation chart exhibiting a complete lack of soundings is given a high risk score. It is entirely possible for a navigation chart to be of the most recent version and current to the latest Notice to Mariners, yet still be entirely devoid of hydrographic information since no survey may have ever been performed in the area covered by the chart.

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The assessment of environmental sensors is made on the basis of whether they are operational or not operational. As these sensors are required carriage on SOLAS vessels the only consideration given is to the increase of risk to conduct a voyage without them.

Assessment of AtoN is made on the basis of their presence along the route of transit to guide the vessel. Although physical AtoN are generally plentiful in well surveyed and well traveled areas, the Arctic has neither of these characteristics. Few physical AtoN and fewer AIS AtoN exist in and around the Arctic except possibly in the immediate vicinity of harbors during the warmer months.

Risk is evaluated by assessing each of the individual capabilities according to the criteria listed and assigning a score corresponding to these capabilities. A total score within the boundaries of low risk indicate that hydrography, navigational charts and sensor capabilities are at or near their optimal state and a voyage under these circumstances may be appropriate if all other criteria for getting underway are met. A total score in the medium risk range indicates deficiencies exist in the recency of hydrographic survey or the presence of AIS AtoN along the route. Neither of these factors may indicate that a problem exists. However, caution should be exercised during transit. A total score greater than 9 indicates a high risk voyage is possible and additional planning and preparation is needed before attempting the voyage.

Risk assessment using emerging technologies – A process for risk assessment using

new technology to supplement existing technology is shown in table 5. Specific reference is made to 3D-FLS to enhance situational awareness into the environment below the waterline by providing a live rendering of the sea bottom and potential hazards to navigation that exist either afloat or within the water column. This system can provide an additional margin of safety when risk associated with a lack of current and comprehensive hydrographic survey is high, and can also provide similar data and functionality as an echo sounder, if necessary.

Further reference is made to the use of Virtual AtoN to replicate physical AtoN and AIS AtoN functions on ECDIS and provide new capabilities for displaying hazards to navigation detected by 3D-FLS that are afloat or in the water column. Capability is provided to lessen the impact of GNSS and AIS service interruptions, spoofing and

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denial of service attacks, and AIS aliasing resulting in misleading position information. This is accomplished through georeferencing to known bottom features and characteristics as depicted in ENC created in accordance with the IHO S-102 standard. Table 5. Alternative risk factors with inclusion of 3D-FLS and virtual aids to navigation.

Risk is evaluated in the same way by assessing each of the individual capabilities according to the criteria listed and assigning a score corresponding to these capabilities. However, there is a difference in the determination of a total score by which risk assessment is made, especially as pertains to hydrography since a live rendition of the bottom configuration can now be viewed in real-time.

The modeled results indicate risk reduction as a consequence of including 3D-FLS to gain insight into the underwater environment and to overcome the limitations of hydrographic survey in areas where no or partial survey was performed, and also using obsolete technologies that provide lower resolution and coverage than modern survey methods. Redundancy in sonar equipment through the use of both an echo sounder and 3D-FLS can also serve to cross-check the performance of each individual system, providing a means to detect sub-nominal performance in either and eliminating a single point of failure that could otherwise go undetected. Further potential risk reduction is possible when an echo sounder is used for navigation through georeferencing to known bottom features and characteristics in conjunction with upgraded ENC developed in accordance with the IHO S-102 standard that supports high resolution environmental models.

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