Table 4 presents the results of repetitive calculations of burned area and final 

 perimeter for several fire shapes and various ratios of the rate of suppression to the 

 forward rate of spread. Also shown in table 4 are the best values of a/r (o) for 

 achieving the minimum burned area or the minimum containment time. The value of 

 a/r (o) which minimizes the burned area does not necessarily simultaneously minimize 

 the°final perimeter length. 



The striking feature of the entries in table 4 is the low values of burned area 

 and perimeter length achievable using this tactic. A comparison of tlie entries in 

 table 2 and 3 with those in table 4 for the same conditions shows that this "indirect 

 attack" tactic does not increase the burned area or extend the time of containment 

 significantly when A/Vp <2, compared to the aggressive tactic of direct attack at tlie 

 liead of the fire. And for such low values of X/V^, this tactic is highly perferable to 

 the tactic of approaching the fire from the back. 



Figures 5 and 6 exhibit the sensitivity of burned area and final perimeter to the 

 choice of first barrier location. The location of the first barrier to minimize 

 burned area will result in a containment time not very different from the minimum value. 

 Conversely, if the barrier is located to minimize containment time, very little area 

 beyond the minimum will be burned. Figures 7 and 8 show graphically the sensitivity 

 of the optimum barrier location to the rate of suppression and fire shaj^e. The 

 similarity of tlie curves in figures 5 and 7 and in figures 6 and 8 again illustrates 

 that the criterion for optimization of the barrier location is not significant if the 

 fire shape, suppression rate, and forward fire spread rate arc known. 



Figure 5. — Sensitivity of 

 burned area to the ahoioe 

 of first barrier location. 



en 



< 



ZD 



SUPPRESSION RATE 

 6 r FORWARD RATE OF SPREAD 



0.9 



0.2 0.4 0.6 0.8 1.0 

 LOCATION OF FIRST BARRIER, a/fo (o) 



15 



