Indicators in the study sites

Table of Contents

1. Compilers and contributors
2. Introduction
3. Climate indicators
4. Water indicators
5. Soil indicators
6. Vegetation indicators
7. Water runoff indicators
   1. Drainage density
   2. Flooding frequency
   3. Impervious surface area
8. Forest fires indicators
9. Agriculture indicators
10. Cultivation indicators
11. Animal husbandry indicators
12. Land management indicators
13. Land use indicators
14. Water use indicators
15. Tourism indicators
16. Human characteristics indicators
17. Institutional indicators
18. Conclusions
19. References

Flooding frequency

Flood frequency is the probability of occurrence of damaging floods in a piece of land during the year. Floods are a function of climate variability (especially rainfall patterns), basin hydrology (including river bed shape), and the intensity of drainage and depth of flow, as well as soil characteristics, particularly water holding capacity of soils. Flooding can be the impact of extensive deforestation, widespread forest fires, overgrazing, collapse of terraces and soil conservation structures, accelerating surface water runoff and flooding intensity on the lowlands. A damaging flood is one that destroys or cause severe damage to the crops, land or infrastructures (Fig. 42a).

Flooding frequency data have been collected from the local administrations, local farmers or by personal estimation. The following classes of flooding frequency have been used for the purpose of this project: (a) never flooding, (b) very rare: once every 10 years, (c) rare: once every 6-10 years, (d) infrequent: once every 3-5 years, and (e) frequent: every 1-2 years.

Fig. 42a. Areas with rare (left) and frequent (right) flooding causing damage to the growing crops and to the land

As Table 5 shows, data on flooding frequency were collected relatively in few study field sites (258 field sites), corresponding to 5 study sites. The number is limited since this indicator was mainly filled in field sites in which soil salinization was the main process of land degradation and desertification. Since most of the questionnaire filled was located in hilly areas, therefore, the dominant class of flooding frequency was very rare or never known, covering 45.0% of the study field sites, corresponding to all sites of Novij Saratov-Russia, and Djanybek-Russia, and in few cases in Boteti Area-Botswana, and Crete-Greece study sites (Fig. 42b). The next important class was frequent (flooding once every 1-2 years), covering 21.7% of the study field sites. Such fields were mainly found in the study sites of Crete-Greece. Very rare flooding frequency (once every 10 years) has been recorded in 15.1% of the study field sites, corresponding mainly to Crete study site. The frequent (once every 1-2 years) flooding frequency was found in 11.2% of the study field sites, corresponding mainly to Crete-Greece study site. Finally, rare frequency of flooding (once every 6-10 years) has been mainly recorded in the Nestos Basin Maggana-Greece study site, covering 6.6% of the total field sites.

Fig. 42b. Distribution of flooding frequency recorded in the study field sites