Fort Bend County Commissioners passed an order prohibiting the sale and use of restricted fireworks June 14 in court. The order was necessary given the extreme dry conditions across the County. Though some citizens may feel this is unfair restriction that will reduce their enjoyment of the July 4th holiday, I think it is very important to realize why a restriction was placed on the sale and use of aerial-type fireworks.
The order prohibits certain fireworks from being sold and/or used in the unincorporated areas of Fort Bend County and was initiated from the drought conditions that are being experienced across the region. The order specifically prohibits the sale or use of “sky rockets with sticks” and “missiles with fins” from being sold or used. It has been determined that the restrictions are needed for these types of fireworks due to the lack of rainfall over an extended period of time and as a method for mitigating the threat of dangerous fires.
How dry is Fort Bend County? Before you answer that question, it is necessary to understand how “dryness” is measured. A standard measure used is the Keetch-Byram Drought Index. This Index, commonly referred to as “KBDI,” was created by John L. Keetch and George Byram as a way of measuring specifically for fire potential. It is a number representing the net effect of evapotranspiration and precipitation in producing cumulative moisture deficiency in upper soil layer. It is a continuous Index relating the the flammability of organic material in the ground.
The KBDI attempts to measure the amount of precipitation necessary to return the soil to full field capacity. It is a closed system ranging from 0 to 800 units and represents a moisture regime from 0 to 8 inches of water through the soil layer. At 8 inches of water, the KBDI assumes saturation. Zero is the point of no moisture deficiency and 800 is the maximum drought that is possible. At any point along the scale, the index number indicates the amount of net rainfall that is required to reduce the index to zero, or saturation.
KBDI levels and its relationship to expected fire potential are reflected in the following table:
• KBDI = 0 – 200: Soil moisture and large class fuel moistures are high and do not contribute much to fire intensity. Typical of spring dormant seasonfollowing winter precipitation.
• KBDI = 200 – 400: Typical of late spring, early growing season. Lower litter and duff layers are drying and beginning to contribute to fire intensity
• KBDI = 400 – 600: Typical of late summer, early fall. Lower litter and duff layers contribute to fire intensity and will burn actively.
• KBDI = 600 – 800: Often associated with more severe drought with increased wildfire occurrence. Intense, deep-burning fires with significant downwind spotting can be expected. Live fuels can also be expected to burn actively at these levels.
So, now that you understand KBDI—- Fort Bend County’s level on the KBDI is currently 703. This number is rising; and with little or no chance of significant rain in near future, the number will likely continue to rise. Just for comparison, here is the KBDI level for some of our neighboring counties: Austin–712; Brazoria–742; Harris–728; Waller–701; and Wharton–671. Perhaps you now understand why local government officials in our area are taking steps to limit use of fireworks during the upcoming holiday season.