FutureThames research highlights 2012

The distribution of drift-filled hollows in London and the Lower Lea Valley empirical model

The distribution of drift-filled hollows in London and the Lower Lea Valley

Engineering works carried out in central London have unearthed a number of features that exhibit curious characteristics.

Drift-filled hollows extend deep into the bedrock geology and are infilled with disturbed superficial deposits and highly weathered bedrock. They can be up to 500 m wide and more than 60 m in depth.

Part of this ongoing work is to produce a new hazard susceptibility map for drift-filled hollows. The map will provide planners with a broader awareness of the potential location of difficult ground conditions associated with these features thereby reducing the potential for unforeseen ground conditions through effective site investigation design.

Pollution in sediments in the Thames basin

The coastal team at BGS are examining a range of legacy pollutants preserved in Thames sediments

The coastal team at BGS are examining a range of legacy pollutants preserved in Thames sediments.

The human impact on sediment quality since the onset of the industrial revolution is investigated by dating sediment cores, measuring contaminant concentrations and assessing the toxicity using microbial toxicity tests.

When combined, this information provides a first step towards an impact assessment of pollutants; knowledge of the timing of pollution events is particularly relevant should the sediments be remobilised during storm events/sea level rise or changing practice.

Integrated groundwater and surface water modelling in the Thames basin

Integrated groundwater and surface water modelling in the Thames basin

The effects of climate change and the human exploitation of our environment pose a serious threat to the sustainability of our water resources, both for ecosystem services and human consumption.

This is particularly true for the heavily populated catchment of the River Thames which consumes 6 million m3 per day of water for public water supply alone.

The catchment has abstraction, nutrient and land use management issues, suffers from both surface water and groundwater flooding, and has experienced severe drought events in the recent past.

We are developing an integrated groundwater and surface water model which covers a number of important groundwater aquifers including the Chalk, Jurassic limestone and Lower Greensand formations, and several of the minor aquifers within the Thames basin.

These systems are unconnected other than through the River Thames and its tributaries. To manage these water resources sustainably and to make robust projections into the future, surface and subsurface hydrological processes must be considered in combination.

This necessitates the simulation of the feedbacks and complex interactions between different parts of the water cycle, and the development of integrated environmental models.

The model integrates a distributed basin-wide runoff-recharge model, river routing model, distributed groundwater model of the Chalk and a semi-distributed model of the Jurassic limestone. All have been integrated using the OpenMI (Open Modelling Interface) standard.

Geological mapping of the Late Cretaceous Chalk Group of southern England: a specialised application of landform interpretation

Expression of chalk formations in farmland

The Chalk forms ranges of hills that are traversed by numerous transportation routes and it lies within the zone of human interaction beneath some densely populated parts of the south-east of England, including the megacity of London.

It is the most important British aquifer in terms of yield and size of dependent population. An understanding of the engineering and hydrological properties of the Chalk and of their spatial variation is essential for infrastructural development and maintenance, and for water resource management.

This new scheme has enabled BGS to convey more detailed information about the composition and structure of the Chalk on their geological maps (and, more recently, in their digital three dimensional geological models), which are therefore expected to be of more practical value, particularly for engineering geologists and hydrogeologists.

Geological field survey and supporting work over almost two decades has demonstrated that nine formations of the Chalk Group can be consistently and systematically mapped throughout most of their outcrop in southern and eastern England.