Temporal analysis: Palaeo
Paleao approaches to the temporal characterisation of hydromorphology
Palaeo approaches examine the geological and archaeological record to establish past hydromophological forms and processes. These techniques are based on sedimentology, stratigraphy and geoarchaeology, and use different techniques (e.g. C-14, OSL, geo- and dendro-chronology) for dating and estimating rates of change. For an overview of the use of palaeo data in fluvial geomorphology, see Jacobson et al. (2003).
Palaeo approaches can be used at all spatial scales and to gain insight into most hydromorphological characteristics. They are the only approach capable of investigating changes in hydromorphological characteristics that have occurred over very long timescales (i.e. millennia). However, this does not imply that they are not relevant to management timescales. Traditionally their temporal resolution was quite poor, but improvements in dating techniques, particularly OSL and dendrochronology, mean that properly constrained stratigraphic layers can now be dated to a decadal or even annual resolution. Consequently, sedimentology and stratigraphy can be used to investigate significant changes in hydromorphological characteristics that occurred thousands of years ago, but they can also be used to document recent changes. Stratigraphic and sedimentological evidence is commonly paired with geomorphological surveys (Section 6.1.1) to shed light on the underlying mechanisms and rates of change.
The accuracy of palaeo approaches is dependent on the techniques used, the skill and experience of the scientist to identify forms and interpret processes, and the level to which sediment strata can be constrained and dated. Specialist texts should be referred to for estimates of accuracy if palaeo approaches are used.