Manual for describing land degradation indicators

Table of Contents

1. Editor
2. Introduction
3. Classification of indicators
4. Land degradation indicators
5. Evaluation and short-list of indicators
6. Explanations for filling the information sheets
   1. General information
   2. Climate indicators
   3. Water indicators
   4. Soil indicators
   5. Vegetation indicators
   6. Water runoff indicators
   7. Forest fires indicators
   8. Agricultural indicators
   9. Cultivation indicators
   10. Husbandry indicators
   11. Land management indicators
   12. Land use indicators
   13. Water use indicators
   14. Tourism indicators
   15. Social indicators
   16. Institutional indicators
7. Farm survey research
8. Focus group approach
9. References

Water runoff indicators

Drainage density: It is defined as the total length of the streams in a drainage basin divided by the area of the basin. Climate affects drainage density both directly and indirectly. The amount and the type of precipitation influence directly the quantity and character of runoff. In areas where precipitation comes largely as thundershowers a large percentage of the rainfall will run off immediately and more surface drainage lines will be formed. Furthermore, climate affects indirectly drainage density by the amount and kind of vegetation growing affecting surface water runoff. Drainage density is greatly affected by the infiltration capacity of the mantle rock or bedrock. It is commonly observed that drainage lines are more numerous over impermeable materials than over permeable ones. Drainage density is also affected by the initial relief or the vertical distance from the initial upland flats to the levels of adjacent graded valleys. In practice the necessary material to carry out this measurement is often not available, and only quantitative estimates can be made. This can be done with the aid of the most detailed material available (maps, aerial photos and satellite images). The following classes of drainage density are used: coarse (<5 km length per km² area), medium (5-10 km km^-2), fine (10-20 km km^-2)and very fine (>20 km km^-2).

Flooding frequency: The flood frequency is the probability of occurrence of damaging floods in a piece of land during the year. A damaging flood is one that destroys or cause severe damage to the crops, land or infrastructure. The following scale can be applied quantitatively where data is available, but will usually form the basis for subjective estimation. Very rare or never: less than once every 10 years or never known to occur, rare: once every 6-10 years, infrequent: once every 3-5 years, frequent: every 1-2 years.

Impervious surface area: Impervious surface area or soil sealing occurs when agricultural or other rural land is taken into built environment. Soil sealing is the result of the development of housing, industry, transport and other physical infrastructure, including utilities (e.g. waste disposal) and military installations. It is defined as the surface area sealed in hectares per 10 km² of territorial surface per 10 years. The following classes can be distinguished: low (<10 ha area sealed in a territorial of 10 km² per 10 years), moderate (10-25 ha), high (25-50 ha), and very high (>50 ha).