Protection against wind and water erosion
Description​
Protection against erosion is the avoidance of runoff from surface layers due to the effects of wind and water and, as a result, the deposition of sediments in undesirable places (built-up areas, rivers, etc.). Protection against erosion is a service mainly provided by vegetation. Plants are able to drastically reduce the amount of erosion through above-ground and underground plant parts.
Required information:
- LS factor is the influence of slope length and slope on erosion. You will find a map for this in the web tool.
- Erosion sensitivity of the soil (K-factor) is calculated based on the soil structure. You will find a map for this in the web tool.
- The erosion sensitivity of the vegetation (C factor) is calculated based on land use.
Qualitative valuation​
To assess the soil's susceptibility to erosion, a qualitative score is calculated taking into account the slope, soil texture and land cover of the area. These 3 factors also appear in the RUSLE equation (Revised Universal Soil Loss Equation), which is one of the most commonly used methods to estimate soil erosion and is also used to build the erosion map of Flanders (Notebaert et al. 2006).
The RUSLE equation is equal to
Formula
where
- A: average soil loss due to channel and interchannel erosion (ton ha-1 year-1)
- R: the rain erosivity factor (MJ mm ha-1 year-1)
- K: the soil erosion susceptibility factor (ton MJ-1 mm-1)
- LS: the topographic slope and slope length factor (dimensionless)
- C: the crop and management factor (dimensionless)
- P: the erosion control factor (dimensionless)
For the qualitative score we take an average of score 1 (score based on LS x K) and score 2 (linked to vegetation (C)).
Quantitative valuation​
To quantify the protection against erosion, we calculate the average soil loss in the current and future scenario using the RUSLE equation and subtract the two from each other.
For the calculation of the LS factor, we refer to the ECOPLAN-SE plugin manual.
Monetary valuation​
We can evaluate the avoidance of soil loss based on the avoided damage caused by mud flows in water and village centers. There are no generic figures available for this.
Numbers to use​
LS factor, R factor and K factor are derived from maps from ECOPLAN and VPO. The P factor is kept constant at 1. The C-factor is calculated using the table below.
Table: score 1 based on LS and K-factor
| SL X K (lower bound <= x) | score |
|---|---|
| 0 | 1 |
| 0.084 | 2 |
| 0.168 | 3 |
| 0.252 | 4 |
| 0.336 | 5 |
| 0.42 | 6 |
| 0.504 | 7 |
| 0.588 | 8 |
| 0.672 | 9 |
| 0.756 | 10 |
Table: score 2 and C-factor for different landuse types
| Land use | C factor | rating 2 |
|---|---|---|
| Grassland and tall herbs | 0.01 | 9 |
| Forests | 0.001 | 10 |
| Heathland and shrubs | 0.01 | 9 |
| Wetland | 0.01 | 9 |
| Flat land and marshes | 0.5 | 3 |
| Rivers and lakes | 0 | 10 |
| Flax | 0.3 | 5 |
| Potatoes | 0.4 | 4 |
| Sugar beets | 0.4 | 4 |
| Ornamental plants | 0.6 | 2 |
| Pumpkins and zucchini | 0.5 | 3 |
| Herbs | 0.5 | 3 |
| Vegetables lowN | 0.5 | 3 |
| Vegetables group 1 | 0.5 | 3 |
| Vegetables group 2 | 0.5 | 3 |
| Vegetables group 3 | 0.5 | 3 |
| Other vegetables and herbs | 0.5 | 3 |
| Rapeseed | 0.3 | 5 |
| Sunflower seed | 0.3 | 5 |
| Other oilseeds | 0.3 | 5 |
| Leguminosa | 0.5 | 3 |
| Other grains and seeds | 0.39 | 5 |
| Maize | 0.5 | 3 |
| Strawberries | 0.5 | 3 |
| Other fruits and nuts | 0.5 | 3 |
| Fodder beets | 0.35 | 5 |
| Other fodder | 0.35 | 5 |
| Silo maize | 0.6 | 5 |
| Other cropland | 0.37 | 5 |
| High density orchard | 0.05 | 8 |
| Traditional orchard | 0.01 | 9 |
| Community garden | 0.5 | 3 |
| Wasteland or agricultural road | 1 | 1 |
| Meadow | 0.01 | 9 |
| Sparsely vegetated land | 0.8 | 1 |
| Wood edge, wooded bank and other tall green conifer | 0.01 | 9 |
| Wood edge, wood bank and other tall green deciduous trees | 0.01 | 9 |
| Pools, ponds and canals | 0 | 10 |
| Verges and other elements of grasslands and brushlands | 0.01 | 9 |
| Other low green | 0.01 | 9 |
| Row of trees | 0.01 | 9 |
| Tree riding lork | 0.01 | 9 |
| Norway spruce | 0.01 | 9 |
| Tree groves | 0.01 | 9 |
| Hedges, shrubs, heathland | 0.01 | 9 |
| Buildings | 0 | 10 |
| Conservatories | 0 | 10 |
| Gardens residential | 0.05 | 8 |
| Gardens other | 0.05 | 8 |
| Roads and squares | 0 | 10 |
| Other high green | 0.01 | 9 |
| Other urbanized area | 0 | 10 |
Source: adapted from Bakker et al. 2008
Assumptions​
- We take an average annual rainfall erositivity of 1250 MJ mm/ha.year for the entire Flanders. This can of course differ locally in reality.
- We keep the erosion control factor P equal to 1. We assume that no measures have been taken to combat erosion.
Translation to an indicator​
We use the quantitative valuation as an indicator: the number of tonnes of soil that is less or more eroded.
An example​
For the example, we refer to the Dutch version of the manual.