CHAPTER 3:  FIRE ENVIRONMENT




3.1 INTRODUCTION

This chapter presents an overview of previous fire activity on Long Island that is extremely useful in understanding current fire trends and suppression requirements. It includes a discussion on how forest fuels (vegetation) and weather conditions influence fire behavior.

3.2 FIRE HISTORY

The importance of fire prior to European settlement is indicated by the presence of fossil pitch pine pollen and abundant charcoal in the sediments of Deep Pond, in the Boy Scout camp at the northern edge of the Central Pine Barrens. It is difficult to determine the exact number of fires, but distinct layers of charcoal in the sediment core indicate that there were at least eight major fires in the past 2200 years. There may have been more numerous lighter or smaller fires that cannot be distinguished individually (Backman 1984). These fires could have been set by lightning and by Native Americans (Central Pine Barrens Joint Planning and Policy Commission, 1995). Reports of fire are common from the time of the very earliest explorers (Morton 1632, Wood 1634).

Large fires became more common after European settlement. Severe and extensive wildfires burned through the Central Pine Barrens repeatedly during the 1800's, with especially large fires in 1839, 1845, 1848, and 1862, 1930's, 1960's, and 1995 (see Appendix B of this document). Many of the early fires may have been caused by sparks from the wood burning engines of the Long Island Railroad; however, arson was a frequent source of the fires (Central Pine Barrens Joint Planning and Policy Commission, 1995).

Fire occurrences since 1930 have been investigated by Windisch (1994), using historic aerial photography, fire department records, newspaper articles, and verbal accounts. Over 130 fires within or near the Long Island Central Pine Barrens (Core Preservation Area and Compatible Growth Areas) were documented and approximately located. About 145 or more additional fires were documented from fire records or other sources, but could not be mapped without better written documentation, or additional aerial photography (Windisch 1994). With the advent of aggressive fire suppression, fires, although still frequent, tend to be smaller than in the past because they are quickly controlled. Several of the largest fires since 1930 are included in the table provided in Appendix B.1.

Two unusually large, severe wildfires, known as the Rocky Point and Sunrise Fires, burned a total of 6,850 acres of the Central Pine Barrens in late August and early September in 1995. Burned areas included a portion of the globally rare dwarf pine plains. The wildfires were unusually severe and large because of extreme drought combined with high fuel loads accumulated in the 65 years since the last major fire. A more detailed analysis and history of wildfires should be developed by the Wildfire Task Force and kept current.

3.3 FOREST FUELS

Fire behavior is governed to large extent by the vegetation involved in the fire. The species composition, structure and amount of fuel determine the fire behavior, the intensity of the fire, its rate of spread and the flame lengths. In the context of fire behavior, the vegetation can be described in terms of fuel models, mathematical models that estimate fire behavior based on vegetation type. Fuels have been classified into 13 different fuel models. The following references to fuel models refer to Rothermel's fuel models developed in 1972 and published in "Aids to Determining Fuel Models for Estimating Fire Behavior" (Hal E. Anderson, 1982). Of the thirteen fuel models, the models described in the following subsection are those applicable to the Long Island Pine Barrens. An excerpt from "Aids to Determining Fuel Models for Estimating Fire Behavior" that explains how fuel models are developed is provided in Appendix B.2 along with a further description of the fuel models applicable to the Central Pine Barrens.

3.3.1 Grasslands

Grassland communities comprise approximately 6 percent of the Core Preservation Area and 5 percent of the Compatible Growth Area. Fuel models 1, 2, and 3 represent these grasslands (depending on height of grass and amount of trees and shrubs). Scattered shrubs may be present. Fire ignition and spread are governed by the fine herbaceous grasses that have cured or nearly cured. These fires are surface fires that move rapidly.

Typical types of vegetation represented by these fuel models include old fields dominated by little bluestem, sometimes with scattered shrubs and trees, and dry coastal plain ponds with herbaceous cover.

3.3.2 Hardwood Forest

Hardwood forests comprise less than one percent in both the Core Preservation Area, and the Compatible Growth Area. Fuel models 8 and 9 represent this forest depending on the amount of dead fuel. These stands consist of mixed hardwoods with scattered pines with little understory of shrubs. The primary surface fuel is loose leaf litter and occasional twigs. The fires are generally slow burning surface fires with low flame lengths, although the fire may encounter a heavy fuel concentration causing a flare-up. High winds can increase the rate of spread of a fire from blowing burning leaves, especially oak leaves.

The dense shrub layer present in the pine-oak forest is absent. Typical examples are closed canopy oak-hickory forest, beech forest and black locust stands found on moister, richer soils. Scattered pitch pines may be present.

3.3.3 Pine-Oak Forest

The majority of the vegetation of the Central Pine Barrens (70 percent of the Core Preservation Area) consists of pine oak forest with a dense understory of flammable scrub oak, blueberry, and huckleberry. These forests are represented by fuel model 6, although this model tends to underestimate fire behavior. Areas in the Central Pine Barrens with an open canopy and an understory of scrub oak are classified as fuel model 4. Within the forests, the dense and continuous shrub layer provides an abundance of fuel throughout the year.

Leaf litter provides a flash fuel and the dead twigs and branches present in the shrub layer ignite easily. Except during spring, leaves of most shrub species will readily burn. The leaves and stems of the shrubs sustain fire and carry heat and flames upward to the canopy. In most stands the dense shrub layer provides a continuous horizontal and vertical source of available fuel. Flame lengths three times the height of the shrub layer are common under wildfire conditions. Crowning and spotting is a danger when pitch pines are present.

Volatile resins in the leaves generate intense fires during the growing season. High accumulations of standing dead shrubs aggravate this situation. Rate of spread, flame length and fireline intensity, under wildfire conditions, often approach or exceed the levels at which hand crews can safely and effectively work.

3.3.4 Dwarf Pine-Scrub Oak Shrubland

Shrubland vegetation dominated by scrub oak and/or dwarf pitch pine comprises approximately 10 percent of the Core Preservation Area, and less than one percent of the Compatible Growth Area. Fuel model 4 represents the shrublands with very little canopy cover. The intertwined scrub oak, dwarf pines, huckleberry, blueberry and bearberry form dense continuous fuel cover that is about six to fifteen feet in depth. Foliage, live and dead twigs and branches carry the fire. Fires are of high intensity and spread rapidly with high potential of spotting. Volatile resins in the needles and leaves generate intense fires during the growing season. High accumulation of standing dead shrubs contributes to intensifying the fire.

The dwarf pine plains in Westhampton is the only example of the combination of scrub oak and pitch pine. Associated with the dwarf pine plains and elsewhere in the Central Pine Barrens are large areas dominated by scrub oak with scattered tall pitch pine.

3.4 ANNUAL FIRE WEATHER

3.4.1 Weather Influence

Wildfire behavior is greatly influenced by local weather conditions. Weather conditions include: relative humidity which affects moisture content of the air and fuels; wind which affects the direction and speed of fire spread; and air temperature which affects the ambient temperature of the fire fuels.

Fire conditions worsen as temperature increases and relative humidity decreases. Wind speeds in excess of 10 mph also begin to increase fire intensity, the rate of fire spread and growth by adverse fire behavior and spotting. Fires become most difficult to control when relative humidity falls below 30 percent.

Data on fire weather is an important tool for both the prevention and suppression tactics of wildfires. This data is available to the local fire departments through Suffolk County Fire Rescue Communications. It is currently calculated by the US Fish and Wildlife Service at the Wertheim Preserve located in the Brookhaven Fire District.

This data consists of a continuous record of pertinent weather conditions and the calculation of the fuel moisture content of 1 hour fuels, 10 hour fuels and 100 hour fuels. The daily readings are analyzed by a special computer program that includes the daily drought index, 10 hour fuel moisture, and wind speed. The longer the area goes without rain, has low relative humidity, high temperatures and low fuel moisture, then the higher the drought index number, and subsequently, the fire weather index.

 
Table 3.1: Drought Index and Fire Intensity
(Index values range from 0 to 800)
0 to 200
Wet condition, low fire intensity
200 to 350
Dry condition, moderate fire intensity
350 to 450
Very dry condition, high fire intensity
Greater than 450 to 800
Drought condition, extreme fire intensity


 
Table 3.2: Ten Hour Fuel Moisture and Fire Intensity 
Greater than 15%
Moist fuel, low fire intensity
7% to 15%
Dry fuel, moderate fire intensity
Less than 7%
Very dry fuel, high fire intensity,
and high possibility of crown fires


 
Table 3.3: Wind Speed and Fire Characteristics
0 to 5 miles per hour
Low flame heights (< 6 feet),
slow fire spread
5 to 10 mph
Moderate flame heights (6 to 10 feet),
moderate fire spread
Greater than 10 mph
High flame heights (> 10 feet),
fast fire spread,
crowning and spotting potential

As this new tool is used, the fire service can develop the local relationship of the fire weather index number to actual fire activity (number of fires, size and severity). Once this relationship is known for Suffolk County, the fire weather index can serve as both a guide for preventive action (limiting public access to park areas, canceling burning permits, public information bulletins, etc.) and a "size-up" tool for Incident Commanders (ICs) on actual wildfires.

3.4.2 Long Island Weather Cycle

Long Island has unique wind patterns due to the large bodies of water surrounding the island (Long Island Sound to the north and the Great South Bay and Atlantic Ocean to the south). Wind breezes are typically sea breezes during the morning through midafternoon and switch to land breezes in late afternoon. This switch can bring about as much as a 180 degree change in wind direction and also a change in wind speed. The unpredictability and uncertainty of local wind directions as well as speeds makes deployment of suppression and standby resources more difficult for the IC. These wind conditions also make the use of "line firing" techniques questionable (and generally not advisable), especially if there are no highly trained and experienced personnel available.

Long Island typically experiences two distinct brush fire seasons. The spring season, late March thru April, typically sees both surface and crown fires. The fall season, late September thru mid-October, typically sees a large number of surface fires of 10 acres or less. Crown fires during the fall season occur more often due to dry or dead leaves still on the trees. The fall season may also include more ground fires making mopup and control more difficult and time consuming.

In recent years, however, unusually dry weather conditions have caused large fires outside the normal wildfire season. In August of 1995, Long Island had its two largest wildfires in recent history (the Sunrise and Rocky Point Fires) and the preceding dry winter (1994-95) also produced large wildfires (i.e., those requiring mutual aid). During the time of the Sunrise and Rocky Point Fires, the local drought index exceeded 500, indicating extremely dry conditions conducive to fire.

Based on Long Island's unique weather patterns and unpredictable fire seasons, the best tool for forecasting wildfire activity is the local fire weather data and drought index. The Wildfire Task Force hopes to continue the availability of this weather data and drought index to local fire chiefs and to develop local data to enhance the value and interpretation of this data for local needs.

3.5 WILDLAND-URBAN INTERFACE

Population increases and the migration of citizens from urban centers to wildlands have complicated the fire protection mission of the local volunteer fire departments in Suffolk County. Years of settlement into the wildlands of Suffolk County and aggressive fire suppression activities have led to increasing fuel levels, increasing the amount of dead fuel per acre. This increases fuel ladders that allow fires to reach conflagration sizes quicker and more frequently. Suffolk County firefighting forces have experienced a change in the type and size of these wildland fires over the past few years. Although wildland fires are not necessarily getting larger, they are burning at a higher level of intensity due to the increasing fuel levels, creating a greater risk to structures, public buildings and natural resources in the interface zone.

A review of other wildland-urban interface fires in the United States indicates there are many common denominators that contribute to major losses of homes and property, loss of lives, injuries, destruction of natural resources, and adverse effects on wildlife habitats and water resources.

The common denominators of these fires include:

Although the above listing is from critiques nationwide, Suffolk County does have some of the conditions listed that could increase the likelihood of a large wildfire conflagration, such as the Rocky Point and Sunrise Fires, to reoccur. This plan, in later sections, includes information on how to address the items listed above. This information will assist in decreasing the intensity of future wildfires and the risk to structures and the public within the wildland-urban interface zone.

3.R RECOMMENDATIONS