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The present Guidelines are one of the outputs of a co-operative effort of PAP/MAP/UNEP, Ministry of Environment/ DGCONA (Madrid), and FAO/AGL, as well as of professional institutions and authorities of Spain, Tunisia and Turkey, relative to the mapping and measurement of rainfall-induced soil erosion process in the region.
The document is intended for:
• experts, professionals and institutions involved in erosion control in the region, for practical application;
• professionals in land use, soil management, water resources management, agriculture and other relevant sectors, for information and general knowledge (additional training would be needed for implementation);
• decision makers in related fields, for information and understanding of their role and responsibilities (in particular: Executive Summary, Part I: Chapters 1, 2.1 and 4, Part II: Chapters 1, 5 and 6, and Annex D; and
• experts, institutions and decision makers involved in Integrated Coastal Area Management (ICAM) in the region (in particular: Executive Summary, Part l: Chapters 1, 2.1, Part II: Chapter 1, and Annex I) for a better understanding of the impacts of erosion on the economy, social conditions and environment, and of the role of erosion mapping and measurement within ICAM.
Soil erosion processes in the Mediterranean coastal areas have serious consequences for rational use of resources and the coastal environment. The fragility of Mediterranean ecosystems, the permanently increasing coastal population, the importance of Mediterranean agriculture and need for higher productivity, and the increased pollution require a comprehensive assessment and evaluation of the erosion phenomena. Mapping and measurement of erosion in affected areas provides the basis for the design and implementation of erosion control and soil management programmes which should be integrated within the ICAM scheme as a broader framework.
With regard to the above, the Mediterranean coastal states, in their role of Contracting Parties to the Barcelona Convention and participants in the Mediterranean Action Plan (MAP), entrusted the Priority Actions Programme (PAP) of MAP with the implementation of a priority action dedicated to "Soil Protection as an Essential Component of the Protection of the Mediterranean Environment". After several years of implementation (1984-1988), that action was focused on rainfall-induced erosion processes. The fact finding phase indicated that, unfortunately, the erosion control activities within countries were based on a number of different mapping and measurement methodologies, most of which incomparable with the others. Therefore, a co-operative PAP-FAO-DGCONA project was formulated and implemented with the participation of Spain, Tunisia and Turkey. The mapping component was implemented in the 1991-1992 period, with some additional mapping performed in 1995-96, with 3 national pilot mappings and the Part I of the Guidelines as principal outputs. The measurement component was implemented in the 1993-1995 period with 3 experimental erosion measurements in selected areas in Spain, Tunis and Turkey, and the Part II of the Guidelines, as principal outputs.
In the introductory part of the Guidelines, the common types of rainfall-induced erosion phenomena with particular reference to Mediterranean conditions are presented, as well as links between mapping and measurement and the process of integrated coastal management.
In the Part I, a common consolidated methodology for mapping of rainfall-induced soil erosion processes in the Mediterranean coastal areas is presented. This methodology has an innovative character. Namely, it allows the presentation of both erosion status and dynamics in a single integrated map. Compared to traditional mapping systems, such an output shows great advantages for erosion control processes and ICAM. According to the common consolidated mapping methodology, the mapping process consists of three phases:
a) Predictive mapping by identifying, assessing and integrating all basic parameters, such as physiography (slopes), lithology and/or soils, land, and vegetation cover, in view of determining preliminary assumptions on erosion risks (erodibility-potential erosion);
b) Descriptive mapping when describing and qualitatively assessing current on-site and active erosion processes. This systematic mapping of qualitative and dynamic erosion features identifies two broad categories of geographic environments: geographically stable, non-erosion affected areas on the one hand, and unbalanced, erosion-affected areas on the other.
c) The consolidation and integration phase, which provides the final cartographic product identifying and assessing both the erosion potential (erosion status) and current erosion process, intensities and trends.
The mapping process is described in detail, and maps relevant to each step are included.
In the Part II, general methods of erosion measurement are presented and commented as a basis for the design of specific measurement activities that should be necessarily adapted to the conditions and particular objectives of each country or sub-region.
A specific, recommended measurement programme and data processing framework is presented in full detail to serve as guide for the implementation of measurement projects in the Mediterranean coastal areas.
The adopted scheme recommends the inclusion into the measurement programme of a group of at least three adjacent catchments of different sizes, up to 20 km2. Some of the smaller catchements should be contained within the larger ones to understand the rules of scale change in sediment transport processes, what is of critical importance for the assessing of erosion impacts in coastal areas. Precise instructions are given about the selection of the catchments and the selection of the measuring points.
Catchment instrumentation is composed of the following elements:
• Runoff control structure. Flume or weir according the circumstances of bed-load transport of the flow.
• Data logger. Two counting channels.
• Water level sensor. An electronic device to convert water level in an electronic impulse. Directly readable by the data logger. Capacitive sensor device is recommended for semi-arid conditions.
• Suspended sediment sampling instrument. Two simultaneous systems recommended:
a) a programmable pumping water instrument triggered by the data logger or other water level threshold triggering mechanism;
b) A syphon sampling device, consisting on a series of bottles at different heights, which takes water samples at various water levels as the hydrograph rises
• Rainfall recording stations. A minimum of one rain recorder per hydrometric station. Tipping bucket mechanism pluviometers connected to data logger recommended.
Field visits programme and laboratory determinations are also thoroughly described.
Data processing and implementation is of critical importance for the success of the measurement programme. The potential sources of error, the procedures for interpolation and extrapolation and the event analysis and temporal integration, receive preferential attention.
Data processing steps, as well as the procedures for numerical and graphical presentation of data, are described using the more common, standard, hardware resources and software tools available, as data base management programmes, spreadsheets and integrated graphic packages.
Finally, in the Part III (Conclusions) it is recommended that the results be presented in three levels: professional/scientific presentation; decision-making level; and information for the general public. The main outputs of an integrated/combined mapping and measurement programme are: maps and their interpretation; measurement results and their interpretation; conclusions on the basis of mapping and measurement results; and recommendations for the follow-up and management/protection measures.
The document also contains 2 annexes: Annex I on the role of erosion mapping within the process of Integrated Coastal Area Management (ICAM); and Annex II - glossary of terms.
The presented erosion mapping and measurement framework has been applied and tested successfully under different sub-regional and national conditions. The prerequisites for its application can be met without special efforts in almost all the Mediterranean countries. However, in any particular case, need may arise for consultation and/or initial training, in which cases FAO/AGL, Ministry of Environment of Spain/DGCONA, or PAP/RAC may be contacted.
It is recommended that the two parts of the Guidelines be used together when formulating and implementing rainfall-induced erosion control programmes or projects.
Finally, there is a good probability that the basic concept of, and approach to the presented mapping and measurement methodology might be applied in other erosion prone regions, after a comparative analysis and adapting of the recommended procedures, as appropriate.