Abstract:
Floodplains in the United Kingdom have evolved from natural landscapes to artificially
modified ecosystems through managing lateral and vertical floodplain connectivity
leading to synergy or trade-offs in ecosystem service delivery. Research methods have
been limited in understanding the processes by which ecosystem service values are
formed and the data required to support ecosystem service assessment. Developing a
methodology while complex and challenging is necessary in order to take the
ecosystem approach forward to support decision making for policy makers, planners
and stakeholders. The aim of this research was to develop a method to assess the
delivery of ecosystem services in response to changes in floodplain connectivity and
evaluate the performance. A case study floodplain was selected at Tempsford,
downstream of the River Ivel in Bedfordshire, United Kingdom as an example for
opportunities to deliver multiple ecosystem services. A sequential integrated modelling
system was applied utilising a linked ISIS 1D-2D hydrodynamic model and WaSim, a
1D soil water balance model to simulate changes in floodplain connectivity and
generate model data to improve estimates of ecosystem services indicators. A non-
monetary multi-criteria analysis methodology was applied to further develop indicators
for ecosystem services assessment and to assess the impacts of the model scenarios
on ecosystem services delivery. The integration of the WaSim model was unsuccessful
as the model performed poorly in the calibration and validation process and was not fit
for its intended purpose. It was deduced that potential groundwater seepage in the
regional aquifer occurs outside of the field study site, which cannot be modelled in
WaSim. To demonstrate the impact of lateral connectivity controls on the water table
position, an empirical method was developed using the mean observed water table
position to represent a ‘no drainage system’ vertical connectivity scenario. The results
showed that in low frequency/high magnitude flood events, increasing the lateral
connectivity by lowering embankments provides synergy and benefits to flood
alleviation, water supply and freshwater fish habitat and trade-offs and disbenefits to
flood damage, agricultural productivity, terrestrial habitat and recreation. In high
frequency/low magnitude flood events, decreasing the lateral connectivity by raising
embankments still provides the same synergy and trade-offs yet lower benefits and
disbenefits. Marginally decreasing the lateral connectivity creates a higher level of
benefits and a lower level of disbenefits to promote multi-functional land use in the
floodplain. Managing the control of floodplain connectivity needs to be carefully
planned to enable multifunctional land use in a floodplain.
