Distributed River Basin Modeling for Analyzing Flood Mitigation Measures under Non-stationary Conditions

Cunha, l. (2009). Distributed River Basin Modeling for Analyzing Flood Mitigation Measures under Non-stationary Conditions. IIASA Interim Report. IIASA, Laxenburg, Austria: IR-09-054

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Abstract

Flood frequency analysis is in the main component of flood risk management projects, influencing pre and post-flood activities. Apart from its importance and the intense research in the area, the available hydrological methods are not adequate, especially under non-stationary conitions caused by land cover or climate change. In this work a new hydrological model is proposed, with the goal of overcome the main weakness of the traditional methodologies.

This research is composed by three main goals. First, the authors attend to add functionalities to an existing calibration-free hydrological model based on the scaling theory of floods. The goal is to provide a better representation of the rainfall-runoff processes that occur in a hillslope scale through the use of empirical models. This model constitutes an important tool for the evaluation of effects of land characteristic changes on flood intensity and frequency.

The second goal is the development of a flood risk framework, with the aim of link hydrological criteria of flood intensity estimation (peak discharge) to criteria that measures flood impact (damages). This activity requires the development of flood maps and the quantification of flood damage. This research presents a simplified methodology for flood risk mapping that can be used for areas with very limited information about the river network. Annual expected damage was used as criteria to evaluate different land characteristics scenarios, being damage estimated by a simple model based on the city parcels structure value and water level-damage curves proposed by FEMA.

The last goal is to develop a simplified case study to demonstrate the model applicability on flood risk management. A case study for Charlotte City, North Carolina was developed. The city has experienced an extensive urban growth since 1960 which has led to significant changes in city's risk and vulnerability to floods. The impacts of urbanization were evaluated using current land cover conditions and two extreme scenarios: pre-development and built-out. The effectiveness of non-punctual flood mitigation measures that are easily harmonized in the urban environment was also evaluated.

The innovative aspect of this study is to present a new methodology for flood frequency analysis that does not require calibration and has the potential to be applied to any region in the world. By this framework a multiple scale analysis of flood peak and flood damage is obtained, prviding essential information for the implementation of an optimal flood risk management policy over different levels of governmental policies (local, regional and global).

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