2.3 – Geomorphology

The Federal District is situated on a regional summit of the Central Plain, which is the remains of levelings resulting from the South American erosion cycles that developed between the Lower Tertiary and the Middle and Upper Tertiary. The relief of the Federal District is characterized by the standard plain to softly undulated, inclined reliefs that extend from the base of the plateaus and the residual hills in direction of the valleys, and dissected reliefs along the Paranoá, São Bartolomeu, Preto, Maranhão and Descoberto rivers. Five large geomorphological compartments can be identified in the Federal District:

• High Plan: plain and softly undulated relief, with altitudes above 1,100 meters and a declivity of less than 10%. These are regions covered with latosols and have low drainage density.
• Intermediate Plan: softly undulated relief, differing from the previous in that it presents a declivity of less than 12% and an altitude of between 950 and 1,050 meters. In this area, cambisols are predominant and there is an elevated drainage density.
• Dissected Valley: undulated and heavily undulated relief, with declivities superior to 20% and an altitude of less than 800 meters. Cambisols predominate and there is a high drainage density.
• Border: Undulated relief with declivities of between 10 and 20% and an altitude of between 950 and 1,100 meters. There is moderate drainage density and the predominance of cambisols.
• Steep Ramps: heavily undulated to sloped relief with declivities above 25% and an altitude of between 800 and 1,100 meters. There is an ample predominance of cambisols and high drainage density.

Altimetry

The altitude of the Federal District varies, approximately, between 750 and 1,350 meters. The altitudes below 900 meters are located in the areas along the São Bartolomeu, Preto and Maranhão river basins. The altitudes between 900 and 1,000 meters occupy, mainly, the central-east and eastern part of the Federal District. Altitudes between 1,000 and 1,200 are predominant, characterized by extensive areas with soft declines. The more elevated portions, above 1,200 meters, are located to the west, occupying a small, continuous stretch.

Declivity

In the Federal District, plane declivities predominate (0 to 3%) and soft undulations (3 to 8%), which occur associated with the higher altitudes. Areas of greater declivity are located in the river valleys, in the São Bartolomeu, Descoberto and Preto river basins (8 to 45%). The greatest declivities occur between the geomorphological compartments, where steep slopes form (>45%).