Paleoflood hydrology is the reconstruction of the magnitude and frequency of recent, past, or ancient floods using geological evidence. The term paleo has contributed to the general misconception that palaeoflood techniques are only used for estimating very old floods (geological scales). However, most of the palaeoflood studies involve the study of prehistoric (last 5000 years), historic (last 1000 years), modern (last 50 years), and even more recent floods in ungauged basins. It is not the time scale of flooding that defines palaeoflood hydrology, but the fact that flood evidence derives from the lasting effects of floods on natural recording indicators (i.e. palaeostage indicators or PSI’s). Common indirect evidence of flood palaeostage includes sediments, erosional landforms (stripped soils, flood scarps, highflow channels), and other high-water marks (drift wood), tree impact scarps, and damage to vegetation (botanical palaeoflood evidence). From societal perspective, paleflood hydrology provides a direct record of the type of floods (largest floods) that are most likely to cost greatest damage.
Paleofloods are closely related to, but can be distinguished from, floods that occurred historically with observed stages; these are termed “historical floods”. In general, paleofloods are indicated by the effects of their passage that remain preserved long for later interpretataion. A flood occurring in a remote area, without gauging records or human observation, can be described as a paleoflood even though it occurred very recently because the magnitude of the flood is reconstructed using geological evidence.
Within the last 30 years, paleoflood hydrology has emerged an important and highly relevant component of earth science with numerous applications to the understanding of flood occurrences and the evaluation of flood hazards.
To reduce risks associated with floods, there is a critical need to increase the length of the extreme flood record beyond that of the instrumental period. The flood record can be extended by hundreds to thousands of years by reconstructing past flood discharges using geomorphological indicators (palaeofloods) and documentary evidence. Palaeoflood hydrology has been employed in many regions of the world for compiling long-term flood records for improving flood risk estimation.
The origin of paleoflood hydrology is associated with the United States, generally from about 1800 to 1982. Palaeoflood records have been reconstructed in southwest USA, Australia, Israel, India, Japan, China, France and central Spain.
Functional Areas of Paleoflood Hydrology:
The primary function in practicing paleoflood hydrology is to extend flood chronologies over period of time, ranging from decade to millennia. Secondary functions include:
o Flood risk (and water supply) estimation using flood frequency analyses with long-term data
o Identifying climate-flood relationships (i.e. do floods cluster in time and whether these clusters are related to varying or changing climates)
o Determining upper bounds of flood magnitudes based on long records.
o Estimating long term recharge in arid land
This course is designed for practitioners to learn about the use of non-systematic data in flood risk estimation. The use of paleohydrologic techniques provides a means of evaluating the hydrologic effects of long-term hydrologic variability and climatic change because it complements existing short- term systematic and historical records, provides information at ungauged locations, and helps decrease the uncertainty in hydrologic estimation.
The objective of this course is to provide participants with an overview of paleoflood hydrology and its application in flood forecasting. For more send mail to email@example.com