| Abstract | This research effort develops an approach to assess intangible flood damage. The proposed "Anxiety-Productivity and Income Inter-relationship Approach (API)" is developed to quantify intangible damages in monetary terms. The tangible damage is a damage that can be directly evaluated in monetary unit while intangible damage cannot. In the past, only tangible damage was considered in the economic feasibility analysis for decision making before project implementation. Therefore, the neglected damage part can be fulfilled if intangible damage is quantified and included. More accurate comprehensive damage assessment can be performed. In general, cost and benefit are concerned as parameters for economic feasibility analysis. In principle, benefit is the output of the investment, but for the case of flood protection project, no output or profit is directly obtained from the investment. On the other hand, damage reduction is calculated and considered as the project benefit. Damage reduction is the difference between the damages before and after project implementation. The general method of economic feasibility analysis for damage analysis is the expected annual damage approach. This existing conventional standard approach is performed by using four relationships: probability-discharge, discharge-flood stage, flood stage-total flood damage and probability-total flood damage relationships. Firstly, the probability-discharge relationship is calculated by using different flood frequency analysis techniques, such as N01mal, Log-No1mal, Gumbel and Log-Pearson Type III distributions. Secondly, the discharge-flood stage relationship generally known as rating curve, is calculated by using water levels in the river and their corresponding discharges. Thirdly, the total flood damage and their corresponding water levels in the river, are needed in order to develop the flood stage-total flood damage relationship. However, only tangible damage paii, which consists of direct and indirect flood damages, is assessed through the conventional assessment method while a proposed API approach is applied to quantify and include intangible damage in monetary unit. The available direct damage-inundation depthflood duration relationships of four land-use types called damage curves, are used to assess direct flood damage. The available damage curves done by Sahasakmontri (1989) were utilized for direct flood damage assessment as well as available method developed by Kates (1965) for indirect flood damage assessment, was applied. Then, flood stage-total flood damage relationship was further developed in this dissertation. Finally, the probability-total flood damage relationship was achieved through the combination of the above three mentioned relationships. This relationship was utilized for expected annual flood damage calculation. This research effort develops and proposes a systematic approach to quantify intangible flood damages in monetary terms. Intangible flood damage can be calculated through four relationships: depth-anxiety, anxiety-productivity, productivity-income and anxiety-time relationships. These relationships are developed by using a multidisciplinary approach based on engineering, social science and economic analyses. In addition, two factors, i.e. Consumer Price Index (CPI) and Hi-tech Innovative and New Inventory Items (HINI), are introduced to help intangible damage evaluation process as accurately as possible. The detailed calculation procedures are precisely performed for easy understanding and to ensure that this API approach is applicable to the real situation under available data in Thailand. Bangkok, the capital of Thailand, was selected as the study area because it had several severe flood events during the last two decades such as flood in 1980, 1983 and the latest flood in 1995. Some major flood protection measures studied by AIT (2000) entitled "Feasibility Study on New Dredging Canal Connecting Khlong Tawee Wattana and Khlong K.hoon Ratpinidjai", are used to be the case studies in order to evaluate total flood damage and to ensure the applicability of API approach. AIT (2000) studied the tangible flood damage for "without" and "with" flood protection measures. The available data of AIT (2000), such as time series data of water level in the study area, topographical map, land-use map and socio-economic data, were utilized in this dissertation. The tangible flood damage of 1983 flood event was assessed and was ensured by comparing with the previous tangible flood damage study done by the National Statistical Office (NSO). In addition, the conventional method for tangible flood damage assessment as well as the API approach for intangible flood damage quantification, were applied for 1995 total flood damage assessment. The 1995 total flood damage assessment was can-ied out under different flood magnitudes equivalent to the flood circumstances in 1980, 1983 and 1995. The expected annual total flood damage for both "without" and "with" flood protection measures, were subsequently evaluated. The reduction of expected annual total flood damage between "without" and "with" flood protection measures known as the expected annual project benefit, was performed in this dissertation. In addition, the expected annual project benefit assessed by "including" the API approach was estimated at 26% increase over the "excluding" situation. The results indicate that not only can conventional flood damage assessment be improved by using the API approach but the total expected annual benefit can also be more accurately estimated. This helps to avoid the underestimation of project benefits, which may result in unfeasible flood mitigation projects and the possibility of inappropriate decision making. |