1 Spatial Modelling of the Terrestrial Environment - Georeferencial

112 Spatial Modelling of the Terrestrial Environment
characteristics (e.g. surface, crown and ground fires). Similarly with approaches to erosion
modelling, both empirical and physically based models have been developed, with
the semi-empirical fire spread model of Rothermel (1972) attaining the most widespread
use. More recently the secondary effects of fires on the atmosphere, hydrology, ecology
and geomorphology of affected regions have started to be modelled, as has the economic
impact. Many of these models are empirical (or contain significantly empirical elements)
because our understanding of the fine detail of the way fire affects atmosphere, vegetation
and soil systems is often poorly understood. Further research is needed into both process
understanding and model development.
The development of GIS brought the first attempts to spatially predict fire growth, however,
it was soon realized that the spatial data needed to parameterize such models were not
available and would be extremely hard to collect. Developments in remote sensing have
alleviated this problem to a certain extent and methods are being developed that allow fire
detection, assessment of burnt areas, fuel load and fuel moisture content. This information
has, in some cases, been integrated with models. For example, burnt area estimates derived
from remote sensing have been used to provide important inputs into models that predict
the quantity of carbon emitted by fires and the quantity of soil eroded after these events.
Though such models provide a significant advance, it has been shown that factors such
as errors in estimated fuel load can introduce a large amount of uncertainty. Therefore,
new methods to accurately derive such parameters are needed. In the final chapter in this
Part (Chapter 9), Wooster et al. introduce a new remote sensing method that holds great
potential in directly measuring the amount of biomass combusted by the passage of a fire.
They introduce a method that models the total amount of energy emitted by the fire, and
show both empirically and theoretically that this can be related to the amount of biomass
combusted and gases emitted. The method holds great promise in overcoming some of the
current limitations to the implementation of the fire models outlined above over large areas.
References
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Fons, W.L., 1946, Analysis of fire spread in light forest fuels, Journal of Agricultural Research, 72,
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Gay, S.P., 1962, Origen distribución y movimiento de las arenas eólicas en el área de Yauca a palpa,
Boletín de la Sociedad del Peru, 27, 37–58.
Rothermel, R.C., 1972, A Mathematical Model for Predicting Fire Spread in Wildland Fuels, USDA
Forest Service Research Paper INT-115.
Wischmeier, W.H. and Smith, D.D., 1958, Rainfall energy and its relationship to soil loss, Transactions
of the American Geophysical Union, 39, 285–291.
Woodruff, N.P. and Siddoway, F.H., 1965, A wind erosion equation, Proceedings of the Soil Science
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Zingg, A.W., 1940, Degree and length of slope as it affects soil loss runoff, Agricultural Engineering,
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