Thanks very much Dirk, and apologies, as I didn't have time to include the base construction as part of the 'tutorial' element of the build.
The base is done quite simply, although it could have been better if I had time to obtain some additional ground-cover materials.
It's a piece of MDF cut to the required size, in this case approximately 18 x 18 inches (MDF, or alternatively, chipboard, is easy to work, and more stable then plywood or other materials), which was then edge-trimmed in inexpensive pine moulding, which was stained after fitting.
The 'concrete' dispersal pan and track were made by drawing the shape onto card, in this case, the box the model came in! This was stuck down using PVA adhesive (white glue), and left to dry with a heavy weight on top, to keep the card flat. (the weight was a couple of large pans filled with water, left overnight!).
Once fully set, the card was marked out with a pencil, each 'panel' being to a known scale size, or approximation to scale. The lines were then scored with a 'Stanley' knife ( a strong-bladed scalpel will suffice) to represent the joints in the 'poured concrete slabs', and then airbrushed, using a thinned mix of Dark Earth enamel.
The paint, being thinned around 60 to 65% thinner to paint, is easily and quickly absorbed by the grey-coloured card, giving the tone of concrete, and the variations in the tones were simply achieved by spraying heavier, repeated patterns where required. The heavier, more obvious 'flaws' in the 'concrete' were created by deliberately smearing thin patches of PVA onto the card before painting, whilst 'soaked in' oil stains and dirt were done with a grease pencil, in this case a ladies eye brow pencil (no funny comments please!)l, then smudged and rubbed in with a finger tip.
Cracks and chips in the 'concrete' were made by either lightly scratching the surface, or drawing with a HB pencil.
The 'bare earth/sparse grass' on the immediate environs of the dispersal is cut from a '00' scale 'ground cover' paper roll, and the 'longer' grass is from a similar roll of static grass matt. Weeds, bushes and hedges were made from a combination of model railway lichen and various foliage materials, and bare patches on the base were treated to a thin coat of PVA and a sprinkling of mixed sand-coloured and green 'scatter' materials (basically dyed sawdust), obtainable from most model, or model railway outlets. These materials are acceptable and passable in 1/72nd scale, although larger scales really require the 'static' grass and 'tufts' available from the same sources.
The actual construction of the 'terrain' is fairly straightforward, the important consideration is blending-in all the elements, so that they appear as natural as possible, without objects seeming to be 'sitting' on top of the ground, rather than being part of the ground. The hut, for example, was glued in place with 'Superglue', after first clearing a shallow 'notch' around the base, so that the walls would 'sink' into the surroundings.
Hope this helps, and, as far as I remember, this part of diorama and scenic work is covered in more detail in the first part of a 'Diorama Guide' I wrote and posted, some time ago, somewhere here in the Modelling section. If I can find it, I might request that it be made a 'Sticky', as it should be a useful starting point for anyone who hasn't attempted this sort of work before.