The Representation of Tidal Creek Connectivity for a Complex Floodplain Topography

Industrial and domestic wastes are frequently released into intertidal zones, either as point or diffuse source inputs. The initial transport of these pollutants in a tidal creek-marsh system cannot be modelled accurately without detailed representation of the tidal creek geometry and the vegetation drag etc. Based on processed DEMs for the integration with the bathymetric data for an intertidal creek, the modelling domain was extended to intertidal floodplains for a case study area, namely the Loughor Estuary, UK. The tidal creek networks extracted from the DEMs were explicitly placed within the mesh-nodes, with densities being referenced to the mesh resolution functions. The elevation dataset was interpolated from the mesh-nodes of the tidal creek vertices, anthropogenic features and floodplains. The bottom roughness of study domain was parameterised based on the characteristics of the principal terrain features. The refined model domain was implemented for the case study modelling of Faecal Indicator Organisms (FIOs) transported from a large area of historically grazed salt marshes. The results showed that the extended domain improved the tidal circulation process and flood inundation details within the intertidal floodplains. The representation of the tidal creek connectivity was included for the FIOs distributions was highly concentrated near the tidal creeks and the adjacent marshes. A two-dimensional unstructured mesh with the sub-mesh-scale details of the tidal creek networks was included, based on the hydraulic characteristics of the floodplains. The results showed improvements in the modelling of flow connectivity for very-shallow water flows with a complex topography.

Keywords: Digital Elevation Models (DEMs), intertidal floodplains, tidal creek networks, sub-mesh scale, connectivity