OR/15/038 Scope of project

Gareth Farr (with contributions from Luz Ramos Cabrera). 2015. Nedern Brook Wetland SSSI Phase 1 hydrological monitoring. British Geological Survey Internal Report, OR/15/038.

This project aims to provide hydrological and hydrogeological monitoring data to address some key recommendations from Haskoning UK Ltd (2013). In black are the proposed actions and in red the work undertaken.

• Set up two monitoring locations on the Nedern Brook for collection of stream stage (level) and flow data; one in the vicinity of the Tyne Cottage observation borehole and another downstream of Caldicot Castle, potentially within the country park. This would enable surface water flows through the study area to be recorded, providing a key data input for the scheme design. Positioning of the gauges in proximity to existing groundwater observation boreholes will enable interactions between groundwater and surface water to be quantified.

New water level data has been collected from three stilling wells in the Nedern Brook. Groundwater level data collected from one piezometer and collated from NRW boreholes and the Great Spring. Gauging has been undertaken in the Nedern Brook to allow stage-discharge calculations to be calculated in the future.

• Undertake site visits to survey water levels and undertake groundwater and surface water monitoring.

Monthly monitoring visits between November 2014 and May 2015 were used to observe the flooding regime, check monitoring equipment, undertake repeat photography of key areas, field water chemistry readings and survey of water levels to maOD (or manual reading of groundwater levels using a ‘dip’ tape). A sketch map of the extent of flooding was made during each field visit.

• Flow within the Nedern Brook to be visually checked from the Castrogi Brook at the Cwm (north of Caerwent ST 45875 92739) to the mouth of the Nedern (ST 48985 87258).

Flow within the Nedern Brook was observed during each site visit.

• Undertake a site walkover along the reach of the Nedern Brook that was lined with concrete, noting the condition of the concrete and areas where cracks are visible or the concrete is missing.

Details are provided from a recent survey undertaken in 2012 for Environment Agency Wales.

• Creation of a 3D Visualization of the Nedern Brook to be used as a tool to engage landowners and members of the public with the monitoring work and flood pattern of the Nedern SSSI. Create 2D flood depth maps to illustrate the maximum and mean flood conditions.
• Provision of scanned field notes and Survey data in Appendix.
• Provision of all hydrological data in excel format.
• Provision of all digital photographs and videos.

Provided in the CD appendix.