天然災害損失之能值評估－－以汐止地區象神颱風為例

EMERGY EVALUATION OF DAMAGES AND COSTS OF XANGSANE TYPHOON IN HSIH-CHIH

當颱風的強度超出一地區所能承受時，其無序（disorder）的能量便對人文系統形成災害。過去對颱風災害所造成的損失多以直接成本估計，或以環境經濟學之主觀偏好判斷衡量環境之損害。本文以「能值」評估方法，由生物物理觀點評估2000年11月1日象神颱風水患對汐止之影響。本文首先利用能值方法分析汐止地區1988年及1998年之生態經濟特性。分析結果顯示，汐止近10年來之開發使得原本屬於汐止地區的環境資源正逐步減少中。因人口成長產生的大量用水、用電與燃料需求、以及廢棄物與棄土的產出，對汐止地區的自然環境加重負荷。此外，汐止的發展未善用河川資源。然後，本文進行象神颱風對汐止影響之能值評估。象神颱風的風能4.95 × 1018 sej，是一般風能的20倍，其帶來的洪災效應是使汐止地區陷入癱瘓的主因。在象神颱風事件中，對整體環境影響最大的能值流量是「河流與洪災」與「固態廢棄物」，各具有4.62 × 1018 sej與4.94 × 1020 sej的能量產出。在都市維生系統方面，以電力系統受創3.37 × 1018 sej較為嚴重。重建需用水泥、砂石及瀝青的能值分別為1.22 × 1020 sej、1.81 × 1016 sej及1.52 × 1015 sej，此量較1998年輸入汐止的貨物能值大。在環境損害中以污泥的量最大，佔4.51 × 1019 sej，為平日汐止年土壤流失量的13倍。象神颱風對汐止之總損害6.73 × 1020 sej接近1998年汐止全年能值使用量。依本研究之情境分析，若汐止地區之行水區未遭受密集開發，則象神颱風之損害將會減輕將近30%。妥善的土地使用規劃為人類適應自然災害之根本之道。

The disordering energy of typhoon will result in hazards to human society. Past research on the damages due to typhoon emphasized on the estimation of direct cost or the application of subjective preference approach of environmental economics. This paper applies the biophysically based emergy synthesis for the evaluation of Xangsane typhoon's effect on Hsih-Chih. First of all, the emergy synthesis of Hsih-Chih during 1988 to 1998 is analyzed to understand its ecological economic characteristics. The result of the analysis indicates that the natural environment in Hsih-Chih has been degraded due to the rapid development during the past decade. Population growth has raised the demand on water supply, electricity, and fossil fuels, and result in the consequential loading on the natural environment. And most importantly, the stream resources has not been well incorporated into the system. The emergy evaluation of Xangsane typhoon is then analyzed to study its effect on Hsih-Chih. As a result, flooding and solid wastes, with the emergy of 4.62 x 1018 sej and 4.94 x 1020 sej respectively, dominate the energy flow of Hsih-Chih during Xangsane typhoon. The emergy value (3.38 x 1018 sej) of the damage on electricity is the highest among urban life supporting infrastructure. The emergy value for the amount of cement, sand and gravel, and asphalt required for reconstruction is higher than imported emergy of Hsih-Chih in 1998. Among the items of environmental damages, the emergy value of mud, 4.51 x 1019 sej, is 13 times as much of the average soil loss in Hsih-Chih. In summary, the emergy value of total damages resulted from Xangsane typhoon, 6.73 x 1020 sej, is almost as much as that of annual emergy flows in 1998. The scenario analysis indicates that if the stream corridor is left undeveloped, the damage of Xangsane typhoon is likely to decrease 30%. It is concluded that adequate land use planning is essential to alleviate the effect of natural hazards.