Hydrodynamic Engine – Soil infiltration parameters

In this section we list the soil infiltration parameters used by various parts of the SCALGO Live system.  For instance, some, or all, of these are used in the Flash Flood Map with infiltration and drainage and in the hydrodynamic integration. We refer to the documentation of those analyses for more information about how and why the soil parameters are used.

Horton parameters

We use the Horton infiltration equation for modeling infiltration, and the table below lists the Horton parameters for the generalized soil types used in SCALGO Live.

To see how the soil types in your country have been mapped to these generalized soil types, please consult the Flash Flood Map white paper linked to in the country specific part of this manual. Note that not all countries have this available at this time. Please contact us if you have questions about availability for your country.

We have split the Horton parameters into "High compaction" and "Low compaction" groups, these groups are based on the land cover map and are defined later in this section. This allows us to select a different set of infiltration parameters for a particular soil type depending on whether it's e.g. in a shallow or dense vegetation area.

Soil type

High compaction

Low compaction

fc

f0

k

fc

f0

k

Rocks and boulders

500

1000

5

2000

5000

5

Gravel

500

1000

5

2000

5000

5

Coarse sand

30

120

5

1000

4000

5

Fine sand

25

100

5

500

2000

5

Coarse sand with clay

21

85

5

85

150

5

Fine sand with clay

20

80

5

50

130

5

Coarse clay with sand

12

50

5

30

120

5

Fine clay with sand

9

47

6

25

100

4

Clay

5

20

5

20

50

5

Fine clay

0,5

2

5

2

20

5

Very fine clay

0,01

0,1

5

0

1

5

Silt

20

80

5

50

130

5

Gyttja/peat

21

85

5

85

150

5

Bedrock

0

0

5

0

0

5

Table: Horton parameters for the generalized soil types used in SCALGO Live

Grouping into high/low compaction

The land cover type of a given location decides whether we use the high or low compaction Horton parameters for that location, the table below details how we map each land cover type to a compaction degree.

Land cover type

Compaction degree

Note

Bare land

High

Shallow vegetation

High

Dense vegetation

Low

Fields

High

Unpaved roads

High

If the native soil type has higher infiltration rates than coarse clay with sand, the cell is applied parameters for coarse clay with sand (assuming this better represents the infiltration through the paving material)

Bare rock

N/A

All rainfall is turned to runoff, zero infiltration

Snow/ice

N/A

All rainfall is turned to runoff, zero infiltration

Table: Soil compaction degrees assigned to different land cover types.