Natural Barrier - an overview (2024)

Designing Security and Layout of Site

Designing security into a new or renovated complex can begin with the exterior or interior. Since we are discussing protective barriers in this chapter, let us assume we started the layout discussion on the outside.

Your main lines of defense are your perimeter barriers or the outer edge to your property line. The second line of defense is the exterior of the building, which includes the roof and roof access and walls, doors, and windows. Remember to eliminate all but essential doors and windows. If this is not done in early stages, they will have to be alarmed and set up as emerging exits. Also included should be adequate lighting (cost-effective) that meets standard and supports exterior closed-circuit TV (CCTV). The third line of defense is the interior. It is important to reduce access points by using access control and have specific areas zoned for access control and added security.

Perimeter Protection

Perimeter protection is effectively the first line of defense in a physical security plan for a facility. However, an examination of the threat assessment of the facility together with the risk management strategy will determine the role of the perimeter in the security management plan. Perimeter security can vary from such items as a white line painted on the ground, to sophisticated high-level perimeter configurations involving multiple barriers with numerous detection systems, permanent surveillance, and continuous patrols. Physical barriers will discourage an undetermined intruder, but will only delay a determined person. Thus, physical barriers must be combined with other security controls for an integrated security solution.

However, fences are not flawless as physical barriers as they will not usually stop vehicle penetration. They are also susceptible to cutting, the nature of their construction assists scaling, and they can be tunneled under unless additional barriers such as plinths can be provided. Fences require a high level of maintenance and usually have a finite life depending on the environment.

Barbed wire can be installed over a chain-link fence by holding it on extension arms installed over the fence. Single-barbed wire can be installed outwards of the perimeter being protected, whereas double-barbed wire is installed on V-shaped extension arms. Barbed wire is installed to provide added difficulty for anyone attempting to scale a fence. For the same reason as barbed wire, concertina or spiral sharp edge wire is also installed on fence extension arms.

Evaluation of penetration times of chain-link fencing have been conducted by the U.S. Army Mobility Equipment Research and Development Command. Chain-link fences with extension poles installed have been subjected to climbing attacks by fit young men to estimate the effectiveness of fences as barriers against penetration. The 2.8ft (2.6m) fence with pole has been penetrated by a man with another man assisting without the use of aids in 4 seconds and the 2.8ft (2.6m) fence with 2.5ft (2.3m) pole was climbed by a man with three men assisting in 2.5 seconds; using carpet as an aid the fastest time was 7 seconds.

Again, a 2.2ft (2m) fence was climbed unassisted and without the use of aids in a time of 3 seconds, and with one man assisting without the use of aids was 1.5 seconds. Finally, a 2.5ft (2.3m) fence was penetrated by a man with one man assisting without the use of aids in 2 seconds. The fastest penetration time with one man assisting using canvas as an aid was 6 seconds (Knoke, 2004).

Chain-link fences with outriggers and barbed wire to increase the level of difficulty for scaling was penetrated with one man assisting without the use of aids in 4 seconds for a 2.5ft (2.3m) fence with barbed wire outrigger, and 5 seconds with one assistant. Also 2.5ft (2.3m) chain-link fences with a collapsible and a double outrigger with one man assisting were 4 seconds (Knoke, 2004).

A chain-link fence is neither crash rated nor intended to stop forcible entry, for example, entry by vehicle or physical cutting. In most cases, a chain-link fence can be easily penetrated by a normal passenger vehicle. As a consequence, target hardening must be installed for facilities where forcible vehicular entry is an issue. A chain-link fence may be enhanced with the aid of crash-rated tension wires threaded through the fence, or with concrete crash structures, or simply by digging a trench around the perimeter of the fence to stop vehicles from reaching the fence.

Perimeter Barrier Access

The defense-in-depth principle ensures that concentric layers of barriers protect the assets of an organization, and that only authorized people have access to the assets. However, access can only be gained to the assets by crossing the barriers in the DiD strategy. Access ways in the barriers are necessary for authorized people to cross these barriers and access the assets. Therefore, the inclusion of gates and doors in barriers are necessary for access to the assets.

There is a wide range of barriers that could be installed as gates allowing vehicle entry ranging from access control barriers in the form of a simple drop arm to a hydraulic crash-rated barrier. The drop arm will only control traffic flow for legitimate users. Therefore, high-security facilities at risk of forcible vehicle entry will need to install crash-rated barriers.

The U.S. Department of State (DOS) standard SD-STD-02.01, Revision A, from March 2003, provides physical testing criteria to certify anti-ram vehicle barriers. This is a performance standard and testing procedure for both active entrance barriers and passive perimeter barriers designated as vehicle impact–rated barriers or anti-ram barriers. The test standard rates the anti-ram barriers within three categories: K12, K8, and K4. The rating of the barrier is determined when a 15,000lb. (6,810kg) gross-weight vehicle impacts a barrier from a perpendicular direction. A K12 rating is achieved when a vehicle traveling at a nominal speed of 50 mph (80 kph) is successfully arrested by the barrier from the perpendicular direction. A K8 rating is achieved for a nominal speed of 40 mph (65 kph); and, a K4 rating is achieved for a nominal speed of 30 mph (50 kph). To be DOS certified at any rating, the penetration of the cargo bed must not exceed 1m beyond the pre-impact inside edge of the barrier (U.S. Department of State, 2008).

However, walls are very expensive to build as security barriers and they take long durations to construct; that is, long-term planning is needed for the construction of walls. Unfortunately, walls present a firm visual barrier for surveillance, so that intruders cannot be observed through the wall, and so are effectively not visible.

Fences

The most commonly used form of barrier, other than the walls of a building, is a fence. Fences vary in type, size, use, and effectiveness. They are erected quickly for a reasonably low cost, as is the case with the basic chain-link fence. They are made more complicated and effective by adding barbed wire or concertina wire, alarm systems, or double fencing with alarmed clear zones between. The type of fence selected and used is determined by the specific needs. Again, balance the costs versus the risks.

If a factory perimeter does not have the advantage of a natural barrier, fencing is necessary. The fencing used can be very typical. For instance, it is 7 feet high and made with 9-gauge wire. It rests no more than 2 inches above the ground and in areas where the soil is loose. A concrete trough/border lies at the base to prevent gaps from erosion or human intrusion. At the top of the fence is a “guard” of three strands of barbed wire placed at a 45-degree overhang that faces away from the property. This actually extends the height of the fence by 1 foot and provides added difficulty for anyone attempting to scale the fence. Naturally, buildings, structures, and trees are sufficiently far away from the fence line as to not offer assistance to those who would attempt unauthorized entry. When looking at enhancing physical security at one of the factory properties, the physical security project leader advised the CSM to consider a “good neighbor” policy. This policy states that the local city planning and beautification commission must also approve any changes made that affect the beauty of the surrounding area.

Walls

Walls serve the same purpose as fences. They are human-made barriers but generally are more expensive to install than fences. Common types of walls are block, masonry, brick, and stone. Walls tend to have a greater aesthetic value, appealing to those who prefer a more gentle and subtle look. Regardless of the type of wall used, its purpose as a barrier is the same as a fence’s. To be most effective, walls ought to be 7 feet high with three strands of barbed wire on top. This will help prevent scaling. For aesthetic reasons, management may resist the use of barbed wire. Nevertheless, it should be seriously considered.

Walls also present a disadvantage in that they obstruct the view of an area. Chain-link and wire fences allow for visual access on both sides; walls do not. This obstacle is overcome by keeping clear zones for several feet on each side of the wall and by using video cameras for observation. Use of roving patrols also increases visibility. When the walls of a building serve as a perimeter barrier in lieu of fencing, the issues are different. Scaling the wall to get to the other side is not an issue, but access to the roof is. Furthermore, controlling access to other openings in the building becomes more critical when the walls to the building are the only outer barrier separating the outside world from the assets requiring protection.

Gates

Gates exist to both facilitate and control access. The most secure perimeter allows no one through. However, that is not practical or desirable; people must come and go. Employees, customers, and other visitors need to have easy access to a facility. Gates allow for this.

Gates need to be controlled to ensure that only authorized persons and vehicles pass through. A variety of controls are used, for example, guards; electronic interactive access control systems, such as card key or password access; or remote control access with video camera observation. What you select depends on your specific needs and conditions (e.g., acceptable risk levels). The number of gates to a facility should be kept to the minimum necessary, not the minimum desired. Controlling gates requires using resources. The more gates used the more resources it will take and the more potential problems are created, because any opening is always a potential vulnerability.

Gates when not in use should be locked or eliminated. Having the flexibility to open an additional gate when traffic demands are high is useful. Eliminating a potential vulnerability is more useful. If a periodic need for an additional gate does exist, when the gate is not in use it must be closed, locked, and monitored. Monitoring is done by video camera by roving patrols, or through the use of an alarm system.

Periodically, even monitored gates require physical inspection to ensure they are operable and secure.

Natural Barriers

The effectiveness of a natural barrier will depend on the barrier itself and how it is used. A body of water may be very effective in keeping pedestrian traffic away from your property but not very effective at keeping boat traffic from your property. In this case, a natural barrier needs to be augmented with a human-made barrier. In any case, natural barriers, like human-made barriers, need to be monitored. Cliff sides can be scaled, water can be crossed, and difficult terrain can be overcome.

Other Openings

Openings not designed for personnel or vehicle traffic are also a concern and must be secured. Needing control are sewage pipes, drains, utility tunnels, large conduits, and heating, ventilation, and air conditioning ducts. Where it is appropriate to lock them, they should be locked. Those that cannot be locked should be monitored. Monitoring is in the form of an alarm system or physical inspection. Any opening larger than 96 square inches should have doors, bars, or grillwork in place to prevent human access. These are installed as permanent or removable, with locking devices. For example, to prevent access through heating, ventilating, and air conditioning ducts, man bars can be installed inside the ducting. This is not practical for openings requiring access by maintenance personnel, where the use of removable grills or doors may be more practical. In any configuration, all openings must be assessed for vulnerabilities and appropriate protective measures implemented. Regular inspections or monitoring to ensure tampering has not occurred is essential.

Design

The three CPTED strategies of territorial reinforcement, natural access control, and natural surveillance are inherent in the Three-D concept. Does the space clearly belong to someone or some group? Is the intended use clearly defined? Does the physical design match the intended use? Does the design provide the means for normal users to naturally control the activities, to control access, and to provide surveillance? Once a basic self-assessment has been conducted, the three Ds may then be turned around as a simple means of guiding decisions about what to do with human space. The proper functions have to be matched with the space that can support them—with space that can effectively support territorial identity, natural access control, and surveillance—and intended behaviors have to be indisputable and be reinforced in social, cultural, legal, and administrative terms or norms. The design has to ensure that the intended activity can function well, and it has to directly support the control of behavior.

Topography

The natural deterrence offered by topography, while often of limited value, should be taken into consideration when designing or upgrading a facility to the maximum-security level. Rivers and other large bodies of water, swamps, escarpments, deserts, and so forth are all examples of natural obstacles that may be used in various ways.

Probably the most famous examples of the optimal use of natural barriers were the prisons on Alcatraz Island in California and the French penal colony on Devil’s Island located off the coast of (then) French Guiana. The physical barriers used to contain the prisoners in these facilities were usually enough to discourage escape attempts. Even if they might be defeated, however, the escapee was still left with no way off the island except by using materials at hand or (in the case of Alcatraz) attempting to swim to freedom. Although both prisons were in operation for many years, only a few escapes were ever successful.

When a facility has a river or other large body of water as a boundary, the natural obstacle may be used in conjunction with more traditional fences as a deterrent. The clear view of the approach route across these areas would discourage an adversary from attempting an approach from that direction, especially if faced with sophisticated alarms and barriers around the objective. In a remote or isolated area, a river or large body of water abutting the site could also serve as adversary approach or escape routes, turning these nominal topographic barriers into liabilities against which additional protection means or procedures must be provided.

The advantage offered by a desert environment is similar to that provided by a natural water barrier. As with water obstacles, the possibility of an unseen approach across a barren landscape is very slim. The advantages of isolation and early detection are outweighed by the fact that approach or escape might be accomplished across the very feature that seems to offer some degree of protection, from any direction.

Swamps, while not usually a consideration in a maximum-security setting, could conceivably be encountered. The principal advantage offered by marshy terrain is its impenetrability to usual forms of ground transportation. The most practical setting for a facility in a swampy area would be at the center of the swamp with only one access road. In the event of successful penetration of the facility, this access road could be blocked to contain the adversaries until outside assistance arrives at the scene.

The security offered by a deep forest should also be considered. When a facility is located in a remote area of dense forest, with very limited and controlled access routes, this remoteness discourages all but the most determined adversaries. As with the natural barriers provided by swamps, forest locations require adversaries to forego the usual methods of transportation when access routes are limited and controlled. This might mean they have to walk in, carrying all the equipment and arms they believe necessary for the successful completion of their mission. In addition, their escape plan must be structured to require, as the last resort, escape by foot. Depending on the remoteness of the objectives, the terrain to be encountered, and the climatic conditions prevailing, these difficulties, when considered above and beyond the resistance to be expected from the on-site security personnel, could force the adversaries to choose another course of action and shift their attention to a more vulnerable target.

In summary, natural barriers may be efficiently incorporated into a total security system only when effective, round-the-clock monitoring of these approach areas by a security guard or CCTV system is provided. Structural barriers physically and psychologically deter and discourage the undetermined, delay the determined, and channel the flow of traffic through proper entrances.

1.1 Mortality Changes over Time

1.2 Declines in Organ Reserve Function with Age

Data from longitudinal studies of aging show a consistent decline in the maximum function of the various organs with age, the decline being essentially linear at a rate of 1.5 percent per year after age 30. Data on maximal performance, such as world record marathon times, similarly show a nearly linear decline with age at the same rate (Fries and Crapo 1981).

Physiologic normal values, however, remain constant with increasing age. Normal pH, blood chemistry, white count, and other homeostatic values do not vary over the lifespan, representing the internal physiologic environment essential for cellular function. However, with the linear decrease in organ reserve in multiple organs, the ability to respond physiologically to a perturbation decreases exponentially. As a result, mortality rates increase exponentially, with a doubling of mortality rates each seven or eight years after age 30 (Fries and Crapo 1981).

With these realities of human aging comes a paradox: the decline in organ reserve is inevitable, yet organ reserve can be increased quite readily, at almost any age (Rowe 1999). For example, an increase in exercise levels can increase cardiopulmonary reserve very substantially, even at advanced ages (Stewart et al. 1993, Fries et al. 1996).

1.3 Enhanced Personal Autonomy and Modifiable Determinism

In philosophic writings, a classical conflict has been between the advocates of free will and those of determinism, and this conflict now exists in modern dress. Determinism is represented by molecular genetics, with the sometime notion that your health over the lifespan is ultimately determined only ‘by your genes.’ Free will is represented by the advocates of health promotion, seeking voluntary changes in behavioral risk factors, such as lack of exercise, cigarette smoking, obesity, and excessive dietary fat; changes which can enhance organ reserve, preserve function, and extend life. In this view, health requires that you ‘take care of yourself.’ The tension between these two paradigms is complex and sometimes uneasy.