Historical flood observation Flashcards
What are the three sources of data that could be used for statistical frequency analysis of extreme floods?
flood marks on historic buildings,
contemporary accounts of notable floods,
photographs and engravings and records of changes in factors such as catchment land drainage or river channel crosssection shape.
Historical records (books, newspapers, picture/artefact), pictoral evidences, flood mark,
Describe the importance of historical data quality check.
▪ It is common that some conflicting statements could be found in the relevant documents.
▪ Cross-checking between different materials should always be carried out if possible.
▪ Since the runoff process in a given catchment is strongly influenced by its soil, landscape, land-use and vegetation changes, it should be expected that the flood characteristics might also change with time.
How could you derive historical floods?
palaeo observations - Sources of palaeo flood data are geological indicators such as flood deposits, silt lines and/or erosion lines found along a river’s channel, valley walls and/or terraces etc
What are the likely sources for palaeo flood records?
Sources of paleo observations - Dendrochronology – study of the tree rings, Geological records
How can you convert historical levels to flood flow?
Manning’s equation
What does “historical” mean in the context of “historical flood data”?
“historical” refers to information not contained within the gauged records, but to a mixture of quantitative and qualitative data such as flood marks on historic buildings, contemporary accounts of notable floods, photographs and engravings and records of changes in factors such as catchment land drainage or river channel crosssection shape.
Examples of historical data fuck ups
confusion between locations
wrong flood marker
different magnitudes of the same flood by different observers.
flood characteristics might also change with time
human influence on the environment
What is the assumption made of instrumental records?
That it is reflective of the past, historical records often suggest that this is a poor assumption
