Temporal analysis: Introduction
An analysis of temporal change supports integrated catchment management and river restoration by providing the following information:
- Previous condition of the catchment, floodplain and channel. For example, information on the channel planform in the past and whether it has changed over time.
- Rates of change in channel and floodplain characteristics. For example, information on how dynamic the system is; whether the channel migrates laterally across the floodplain; and if so, how quickly it migrates, and whether this rate has changed over time.
- Identification of human pressures and how they have changed over time. For example, whether land cover or use has changed; and if so, when these changes occured, and whether they have intensified, diminished or changed in spatial extent.
- Channel response to past natural disturbances and human pressure. This type of information helps to appraise the current condition of the river and floodplain, the responsiveness of the river to external forcing, and where it sits in relation to thresholds for change in river patterns.
- Evolutionary trajectories. By analysing the previous channel conditions, how the river has changed over time, and its links to external pressures, it is possible to have a better understanding of its past evolutionary trajectory and to start to predict likely future river channel and floodplain changes under a range of management scenarios.
The purpose of chapter 6 of REFORM Deliverable 2.1 is to summarise the techniques used to investigate change in hydromorphology over time. Recommendations are provided on the approaches to use for each characteristic, the range of data that can be collected using those approaches, suitable analytical techniques, and a general discussion of the impacts of data reliability on the interpretation of temporal change.
For example applications of temporal characterisation refer to REFORM Deliverable 2.1 (Part 3) describing catchment case study applications. The River Frome case study, in particular, provides full details of how every stage was undertaken, including some guidance on which ArcGIS functions to use.