Flood Modelling and Visualisation

Continuing to explore the possibilities of using PixelActive's CityScape for modelling flooding I've gone back to some old data documenting particularly impressive floods on the River Trent, in Leicestershire, in December 1954.

This wonderful RAF air-photograph, taken at about 11am on 15th December shows the Trent in full flood, with substantial overbank flooding affecting both the north and south of the river and the area to the south (Lockington Marshes) almost completely inundated.  A south-bound express train can be seen, most visibly by its train of steam, about to cross the Trent.  But how deep was the flooding.  Some while ago we calculated the extent of the floods by comparing the photographic evidence with recent lidar terrain data.

Lidar Terrain Model.

"Flooded" lidar (in blue) superimposed on air-photograph.

Together, these two allow us to duplicate the photographically documented flooding by selective colouring of the lidar data. By our estimates the river level at Lockington was up to 1.2m above its usual winter level.  So what about visualisation?  Using Cityscape and the lidar DTM (exported as a binary grid from ArcGIS, which overcomes the GeoTiff issues) it is possible to flood the terrain to roughly duplicate the level of inundation of December 1954.

Floods of 1955 simulated in CityScape

Moving from the 2D map view CityScape allows some nice 3D visualisation of the extent and character of these floods.

Looking north-east from an earthwork platform which  

probably served as a livestock refuge.

Overlooking Sawley Cliff Farm, isolated by floodwaters.

Sawley Cliff Farm was abandoned not long after the 1954 floods and the whole area remains prone to periodic flooding.  The Lockington marshes have formed the study area for intensive research into river channel formation processes and the relationship between archaeology and dynamic river systems. Does visualisation such as this contribute to such studies? I'm not sure at present, although it may  at least open up the area to other, more visually oriented audiences.  Of course these visualisations are simply the here and now (well almost), perhaps more interesting would be to recreate the river-scape of 2000 years ago, channel movement, vegetation, environment and settlement, and then explore the impact of the dynamic River Trent on that.

Climate Change, Archaeology and City Modelling

I've been continuing to explore Pixel Active's excellent CityScape, particularly as its focus on urban modelling takes me into new realms of visualisation.  The ability to import OpenStreetMap mapping and SketchUp models makes rapid visualisation of many cities easy.  Below, is a quick (really quick, about 10 minutes work) model of a corner of my old home, York.  Interesting, if a little quirky and certainly in need of more work.

On adding the River Ouse to my rough landscape, it struck me that CityScape's global water level functions would allow me to flood the landscape. Memories of York's dramatic winter 2000/2002 floods prompted the following crude visualisations of somewhat more water around Clifford's Tower than I remember.

Although this crude visualisation lacks an underlying terrain model, and so any pretence of credibility, it strikes me that this function might be adapted to look at one impact of future climate change in river valleys; flooding. Climate change and cultural heritage has concerned me and other colleagues elsewhere and with other hats on, but perhaps visualisation might bring home the potential real impact of climate change on cultural heritage more than words alone.  

Painting the Landscape

A request to provide images of Stonehenge with the Cursus barrow group in the background had me pondering the limitations of my Ordnance Survey based terrain model, which of course includes no such details.  In the absence of lidar terrain data for the study area (unless of course English Heritage would like to hand some over)  I've come up with an inexact compromise.

Using the Ordnance Survey mapping, which shows barrow locations, I've created a binary mask in ArcGIS in which the earthworks of barrows are shown in solid black.

Imported into CryEngine as a texture mask, and with a suitably garish texture, this serves as a visual guide for manually tweaking the terrain with Sandbox's terrain modification tools, in effect painting the barrows on to the landscape.  With sensible textures restored things begin to look reasonable.

The results are not so bad, with correctly located barrows that, with care, can be sculpted into approximately the right size and profile.  Better of course to begin with accurate survey data, but for now at least this meets the requested need.

Vegetation and Views: Leskernick Revisited Pt. 3

Leskernick in CityScape

Back to the theme of investigating the landscape of Leskernick on Bodmin Moor.  The rapid landscape modelling facilities of PixelActive's CityScape, coupled with its rather wonderful cloud modelling facilities tempted me to explore using it to model part of Bodmin Moor.  So, here is a rough first attempt at visualising my 16 x 16km study area.  I've found that CityScape's import of GIS terrain data in Geotiff format is a little uneven, perhaps an issue with ArcGIS's implementation of Geotiff  as I've experienced similar problems with other Arc derived Tiffs in the past.  To get around this I've used a greyscale heightmap, "baked" onto a terrain set up with a frame of correct dimension and projection derived from a shapefile.  This seems to work well.  So, below, in homage to the original photograph, a rapid visualisation of the view through "Bender's door".  Interesting to note how changing atmospherics alter the viewing distance as the near horizon recedes into cloud.

I'll be experimenting more with CityScape for this project as I feel sure that it has much to offer and although lacking the first-person avatar-based facilities of CryEngine, its rapid landscape modelling and realistic clouds are perhaps more suited to this endeavour.