The document discusses the creation of a digital terrain model of the Nishava River Basin between Bulgaria and Serbia. A methodology was used to create a raster grid terrain model based on horizontal coordinate points and altitude data. As a result, two types of digital terrain models were generated: one with a 30m cell size covering the entire study area, and one with a 5m cell size focusing on key risk areas. The models will help assess flood risk and support sustainable development in the upper Nishava catchment region.

1. IPA CBC Programme Bulgaria - Serbia
Creation of digital terrain model of Nishava River Basin
The creation of digital terrain model of certain parts of the Nisava River Basin is the
third major task of the flood hazard and risk mapping.
Specifically for this project the following methodology was used:
The DTM is created based on established horizontal points and altitude. It is created
in raster (grid) format and is obtained by topogrid function of ArcGIS workstation. The
grid-based models are the simplest and most convenient for practical application of
digital terrain models, as developed on the basis of uniformly distributed starting point
of altitude data. With this type of models, the field with coordinates X, Y is a
rectangular grid formed by intersecting each vertical (at x1, x2, ..., xn) and horizontal
(with y1, y2, ..., ym) lines. Function of the altitude is created for each square cell [xi,
xi +1] × [yj, yj +1] set in the corners of the cell values of the sea level altitude zi, j, zi
+1, j, zi, j +1 , zi +1, j +1
The result is a statistical surface in raster grid format and has the following form:
Digital Grid Terrain Model
Most often, GIS visualization of the relief is achieved by overlapping two layers, one
of which is a raster pattern with values for the altitude, and the second - surface,
reflecting the shade of the topographic surface.
EUROPEAN UNION
Bulgaria – Serbia IPA Cross-border Programme
“Assessment of flood risk – a base for sustainable development in upper part of Nishava
catchment”
Page 1

2. IPA CBC Programme Bulgaria - Serbia
A raster terrain model is laid on the surface containing the shade of relief, which turns
the gradient scale (usually from green to brown).
Achieved results
As a result of the work, the following types of digital terrain models are generated:
EUROPEAN UNION
Bulgaria – Serbia IPA Cross-border Programme
“Assessment of flood risk – a base for sustainable development in upper part of Nishava
catchment”
Page 2

3. IPA CBC Programme Bulgaria - Serbia
• Digital terrain model throughout the study, cell size 30 m
 Digital Terrain Model of the key risk areas, cell size 5 m
EUROPEAN UNION
Bulgaria – Serbia IPA Cross-border Programme
“Assessment of flood risk – a base for sustainable development in upper part of Nishava
catchment”
Page 3

4. IPA CBC Programme Bulgaria - Serbia
This publication was elaboraed with the assistance of the European Union, through IPA
Cross-border co-operation programme
CCI No 2007CB16IPO006.
The contents of this publication is a responsibility of the SRD-SU „St. Kliment Ohridski” and
should in no way be accepted as a statement of the European Union or the Managaing
Authority of the programme.
EUROPEAN UNION
Bulgaria – Serbia IPA Cross-border Programme
“Assessment of flood risk – a base for sustainable development in upper part of Nishava
catchment”
Page 4