Topography as a soil forming factor is related to the soil's position on the landscape. Topography refers to the shape or contour of the land surface. Some soils are going to occur on the summit of a slope, some on the side slopes and some on the footslope. The position of the slope will have a great deal to do with the soils characteristics.
A typical slope profile
would look like this: 
In general soils at the summit and backslope develop horizons the fastest. Soils on the shoulder develop slower because
-
rainfall will run off
this slope position faster,
there will be more soil
erosion ,
and there will be less
leaching.
At the footslope position the soils will collect sediment from upslope that can bury the horizons and slow down their development. If sediment is minimal, than the increased water accumulating on the footslope will increase the leaching and the depth of horizon development.
Another complicating factor is the depth of the water table in relation to the slope position. This concept of soils being different because of the depth to the natural water table is called the"Catena Concept" or soils have different properties due to their depth to the water table.
This diagram indicates this
relationship. Soils that are greater than 4 feet to the water table are
considered 
Well Drained (WD) and do not have any characteristics that indicate
poor drainage. These features are called redoximorphic features and are
reflected in the soil as splotches of red or gray color and are called
mottles. Well drained soils have mottles greater than 4 feet.
Soils that are Moderately
Well Drained (MWD) have gray and red mottles between 3 and 4 feet
These mottles indicate that the water table will be at this level during
some periods of the year. For the Somewhat Poorly Drained (SPD)
soils the mottles will occur from 2 to 3 feet. For the Poorly Drained
(PD) soils the entire soil below the dark surface will be gray in color.
Indicating that most of the iron has been reduced due to the low O2 levels.
A typical profile of a poorly drained soil would look like this.
Note the gray colors immediately below the dark surface. Poorly drained
soils occur in depressions and low areas. Many areas of Minnesota prior to
settlement consisted of these kind of soils that today are known as
wetlands. An area to look for wetlands is north of the Twin Cities on the
Anoka Sand Plain. Here wetlands consisting of the Isanti Soil are
interspersed with the well drained Zimmerman Soils
.
The last component of
topography is the aspect of the slope or the direction the slope faces.
This
is important where the slopes are steep enough to allow the southern
aspect to become hotter from the direct rays of the sun. As this occurs
more water is evaporated and less leaching occurs, thus less soil
development takes place on southern exposures. In southeastern Minnesota
these southern exposures
In summary, topography affects soil development by the location of the soil on the slope profile, the direction the steep slope faces, and the depth to the water table.
Information provided by: http://www.soils.agri.umn.edu