1.2 Coordonnées des personnes-ressources et des institutions impliquées dans l'évaluation et la documentation de la Technologie

Nom du projet qui a facilité la documentation/ l'évaluation de la Technologie (si pertinent)

Book project: Making sense of research for sustainable land management (GLUES)

Nom du projet qui a facilité la documentation/ l'évaluation de la Technologie (si pertinent)

Sustainable Coastal Land Management (COMTESS / GLUES)

Nom du ou des institutions qui ont facilité la documentation/ l'évaluation de la Technologie (si pertinent)

University of Oldenburg (University of Oldenburg) - Allemagne

1.3 Conditions relatives à l'utilisation par WOCAT des données documentées

Le compilateur et la(les) personne(s) ressource(s) acceptent les conditions relatives à l'utilisation par WOCAT des données documentées:

Oui

1.5 Référence au(x) Questionnaires sur les Approches de GDT (documentées au moyen de WOCAT)

2.1 Courte description de la Technologie

Définition de la Technologie:

Water retaining polders to reduce flood risk due to heavy rainfall or runoff at high tide in embanked coastal lowlands. Delineation of the retention area and land use within the retention area was developed in a participatory process with local experts.

2.2 Description détaillée de la Technologie

Description:

In the 19th and 20th century land was reclaimed from the sea to make use of the exposed fertile soils for agriculture through a process known as ‘impoldering’. The reclaimed land is now characterized by intensive grazing and cropland. This is a region where agriculture is the most important form of land use. However, the land needs to be regularly drained. Given the expected increase in precipitation in winter due to climate change, the corresponding increase in freshwater discharge needs to be managed. Furthermore, the periods when natural discharge into the sea oc-curs are likely to decrease – because of rising sea levels also caused by climate change. Consequently, in winter and spring, greater quantities of freshwater will need to be pumped into the sea rather than discharged naturally at the low or ‘ebb’ tide. Specially embanked water retention polders will be required to temporarily impound water as part of a multifunctional approach to coastal zone management.

Purpose of the Technology: These retention polders could be a cost-effective alternative to expensive invest-ments in extra pumping capacities to prevent submergence of low-lying cultivated areas. The primary aim is to restrict floods to the retention polders when the drain-age network is overburdened and cannot deal with the predicted extra demands in the future. The high evapotranspiration from the open waterbody, and the reeds growing within, will also help with reducing the amount of water. During dry sum-mers, the water in the retention polder could also be put to creative use as a source of irrigation. Another potential advantage is that subsurface saltwater intrusion in the region could be prevented by the freshwater-filled polders. During extreme storm surges and in the rare case of breaches in the sea wall, the retention polders would serve as an extra line of defence by holding seawater.

Establishment / maintenance activities and inputs: An embankment enclosing approx. 500 ha will be able to store up to 2,500,000 m³ of water. This will improve the drainage of an area of approx. 49,000 ha. The invest-ment for building this water retention area is high – but for the reasons stated it serves a necessary purpose at a cost which is lower than the alternative – increased pumped drainage installations. Maintenance costs will be lower than the drainage alternative as only the integrity of the embankment needs to be monitored regularly. Currently, agricultural land use within the polders is adapted to higher water levels and occasional flooding. Within the embanked area there will be a change from the current use of mainly crop land to extensive grazing, open water and reed stands.

Natural / human environment: Some parts within the retention polder will be used for agricultural purposes, while the wetter parts will be set aside. In these latter sections, undisturbed natural regen-eration will take place. A landscape comprising various different elements, without any extreme forms of intensive land use such as large areas of monocultures will be the result. Thus requirements for agricultural use and tourism will be addressed.

2.3 Photos de la Technologie

2.5 Pays/ région/ lieux où la Technologie a été appliquée et qui sont couverts par cette évaluation

2.6 Date de mise en œuvre de la Technologie

Si l'année précise est inconnue, indiquez la date approximative: :

• il y a entre 10-50 ans

2.7 Introduction de la Technologie

Spécifiez comment la Technologie a été introduite: :

• au cours d'expérimentations / de recherches
• par le biais de projets/ d'interventions extérieures

3.2 Type(s) actuel(s) d'utilisation des terres, là où la Technologie est appliquée

Les divers types d'utilisation des terres au sein du même unité de terrain: :

Oui

Précisez l'utilisation mixte des terres (cultures/ pâturages/ arbres):

• Agropastoralisme (y compris les systèmes culture-élevage intégrés)

Commentaires:

Major land use problems (compiler’s opinion): Flood events and droughts may substantially disrupt the contemporary land use in the future and lead to higher drainage costs and higher economic risks for agricultural production. This may reduce the ecological and economic viability of the current intensive and highly productive land use under a changing climate.

Major land use problems (land users’ perception): There is no awareness of risks due to climate change in the land users point of view.

Cut-and-carry/ zero grazing: cows for milk

Improved pasture: cattle for milk and meat

Future (final) land use (after implementation of SLM Technology): Other: Oo: Other: wastelands, deserts, glaciers, swamps, recreation areas, etc

Constraints of infrastructure network (roads, railways, pipe lines, power lines): needs to be adapted to regular flooding

Constraints of recreation (landscape is used for recreation and tourism ): change in landscape due to retention area

Constraints of nature conservation area (protected sites): wetter conditions in retention area

Number of growing seasons per year: 1
Longest growing period in days: 240Longest growing period from month to month: March to October
Livestock density: > 100 LU /km2

3.3 Est-ce que l’utilisation des terres a changé en raison de la mise en œuvre de la Technologie ?

Est-ce que l’utilisation des terres a changé en raison de la mise en œuvre de la Technologie ?

• Oui (Veuillez remplir les questions ci-après au regard de l’utilisation des terres avant la mise en œuvre de la Technologie)

Commentaires:

Mixed: Mp: Agro-pastoralism

3.4 Approvisionnement en eau

Commentaires:

Water supply: rainfed, mixed rainfed - irrigated

3.5 Groupe de GDT auquel appartient la Technologie

• gestion des eaux de surface (sources, rivières, lacs, mers)
• gestion/ protection des zones humides

• Flood prevention

3.6 Mesures de GDT constituant la Technologie

Commentaires:

Main measures: structural measures

Secondary measures: management measures

3.7 Principaux types de dégradation des terres traités par la Technologie

Commentaires:

Main type of degradation addressed: Hs: change in quantity of surface water

Secondary types of degradation addressed: Cs: salinisation / alkalinisation, Hg: change in groundwater / aquifer level, Hq: decline of groundwater quality

Main causes of degradation: change of seasonal rainfall (Climate change, higher rainfall in winter, lower in summer), Heavy / extreme rainfall (intensity/amounts) (Heavy rainfall in winter due to climate change expected), floods (Flooding due to heavy rainfall in winter)

Secondary causes of degradation: droughts (Droughts due to less rainfall in summer (climate change)), other natural causes (avalanches, volcanic eruptions, mud flows, highly susceptible natural resources, extreme topography, etc.) specify (Sea level rise)

3.8 Prévention, réduction de la dégradation ou réhabilitation des terres dégradées

Spécifiez l'objectif de la Technologie au regard de la dégradation des terres:

• prévenir la dégradation des terres
• réduire la dégradation des terres

Commentaires:

Main goals: prevention of land degradation

Secondary goals: mitigation / reduction of land degradation

4.1 Dessin technique de la Technologie

4.2 Informations générales sur le calcul des intrants et des coûts

autre/ monnaie nationale (précisez):

Euro

Indiquez le taux de change des USD en devise locale, le cas échéant (p.ex. 1 USD = 79.9 réal brésilien): 1 USD = :

0,94

4.3 Activités de mise en place/ d'établissement

	Activité	Calendrier des activités (saisonnier)
1.	Building of dams	during winter months

4.4 Coûts et intrants nécessaires à la mise en place

	Spécifiez les intrants	Unité	Quantité	Coûts par unité	Coût total par intrant	% des coût supporté par les exploitants des terres
Main d'œuvre	Labour	Dam	1,0	10000000,0	10000000,0
Equipements	Machine use	Dam	1,0	4000000,0	4000000,0
Matériaux de construction	Earth	Dam	1,0	112000,0	112000,0
Coût total de mise en place de la Technologie					14112000,0
Coût total de mise en place de la Technologie en dollars américains (USD)					15012765,96

Commentaires:

Duration of establishment phase: 3 month(s)

4.5 Activités d'entretien/ récurrentes

	Activité	Calendrier/ fréquence
1.	Control of dams	once a year
2.	Maintenance of dams	once a year
3.	Maintenance of drainage system	once a year (mean of many years)

4.6 Coûts et intrants nécessaires aux activités d'entretien/ récurrentes (par an)

	Spécifiez les intrants	Unité	Quantité	Coûts par unité	Coût total par intrant	% des coût supporté par les exploitants des terres
Main d'œuvre	Labour	Dam	1,0	500,0	500,0
Equipements	Machine use	Dam	1,0	200,0	200,0
Matériaux de construction	Earth	Dam	1,0	100,0	100,0
Autre	Maintenance per km ditch	Dam	1,0	2270,7	2270,7
Coût total d'entretien de la Technologie					3070,7
Coût total d'entretien de la Technologie en dollars américains (USD)					3266,7

Commentaires:

Machinery/ tools: digger, open truck

The main investment is based on a dam length of 13 km to build up the retention area of a size of 500 ha. The length of the drainage network for the whole watershed (retention area and the surroundings) is 1,134 km. Maintenance costs of drainage network are based on long term annual mean cost of 2,270.72 Euro per km including pumping costs.

4.7 Facteurs les plus importants affectant les coûts

Décrivez les facteurs les plus importants affectant les coûts :

The establishment costs are for the whole retention area (500 ha). The establishment period will be half a year.
Mainly the elevation in the region determines the costs as the height of the dams depend on the elevation. Typical heights are 1 m up to 2 m with a slope of 1:3.

5.1 Climat

5.2 Topographie

5.3 Sols

Si disponible, joignez une description complète du sol ou précisez les informations disponibles, par ex., type de sol, pH/ acidité du sol, capacité d'échange cationique, azote, salinité, etc.

Soil fertility is high
Soil drainage/infiltration is meidum
Soil water storage capacity is high

5.4 Disponibilité et qualité de l'eau

5.5 Biodiversité

5.6 Caractéristiques des exploitants des terres appliquant la Technologie

Indiquez toute autre caractéristique pertinente des exploitants des terres:

Land users applying the Technology are mainly common / average land users

Population density: 50-100 persons/km2

Annual population growth: < 0.5%

1% of the land users are very rich and own 1% of the land.
49% of the land users are rich and own 24% of the land.
50% of the land users are average wealthy and own 50% of the land.
and own 25% of the land.

Off-farm income specification: Many farmers do additional work in companies

5.7 Superficie moyenne des terres utilisées par les exploitants des terres appliquant la Technologie

5.8 Propriété foncière, droits d’utilisation des terres et de l'eau

Propriété foncière:

• individu, sans titre de propriété

Droits d’utilisation des terres:

• individuel

5.9 Accès aux services et aux infrastructures

6.1 Impacts sur site que la Technologie a montrés

Impacts socio-économiques

Production

Revenus et coûts

Autres impacts socio-économiques

Impacts socioculturels

Impacts écologiques

Cycle de l'eau/ ruissellement

Sols

Biodiversité: végétale, animale

Réduction des risques de catastrophe et des risques climatiques

6.2 Impacts hors site que la Technologie a montrés

6.3 Exposition et sensibilité de la Technologie aux changements progressifs et aux évènements extrêmes/catastrophes liés au climat (telles que perçues par les exploitants des terres)

Changements climatiques progressifs

Changements climatiques progressifs

	Saison	Augmentation ou diminution	Comment la Technologie fait-elle face à cela?
températures annuelles		augmente	bien

Extrêmes climatiques (catastrophes)

Catastrophes météorologiques

	Comment la Technologie fait-elle face à cela?
pluie torrentielle locale	bien
tempête de vent locale	bien

Catastrophes climatiques

	Comment la Technologie fait-elle face à cela?
sécheresse	bien

Catastrophes hydrologiques

	Comment la Technologie fait-elle face à cela?
inondation générale (rivière)	bien

Autres conséquences liées au climat

Autres conséquences liées au climat

	Comment la Technologie fait-elle face à cela?
réduction de la période de croissance	pas connu

6.4 Analyse coûts-bénéfices

Quels sont les bénéfices comparativement aux coûts de mise en place (du point de vue des exploitants des terres)?

Quels sont les bénéfices comparativement aux coûts d'entretien récurrents (du point de vue des exploitants des terres)?

Commentaires:

The benefits will be visible in an longer time frame. There will be benefits of the investments when considering sea level rise in the upcoming 100 years.

6.5 Adoption de la Technologie

Commentaires:

Comments on spontaneous adoption: The SLM Technology is not implemented by land users but needs to be implemented in spatial planning of the federal state. We expect that there is a chance for implementation.

There is a strong trend towards spontaneous adoption of the Technology

Comments on adoption trend: The SLM Technology was developed together with regional experts. It seems that the ideas developed, merge more often in their recent discussion and an implementation is likely.

6.7 Points forts/ avantages/ possibilités de la Technologie

Points forts/ avantages/ possibilités du point de vue de l'exploitant des terres
The retention area will supplement the drainage of the arable fields and pastures outside the retention area How can they be sustained / enhanced? Combine with other technical solutions for protection against flooding.

Points forts/ avantages/ possibilités du point de vue du compilateur ou d'une autre personne ressource clé
Prevention of flooding during strong rainfalls and possibility to irrigate during dry periods How can they be sustained / enhanced? The larger the retention areas are the more water can be stored
Prevention of salt water intrusion in the region How can they be sustained / enhanced? Fresh water in the retention areas prevents saline ground water from intrusion. Build polders in areas where saline ground water intrudes.
Endangered species might obtain new habitats in the retention area How can they be sustained / enhanced? Extensive land use can help to optimize the habitats for endan-gered species and increase attractiveness for tourism.
Through investments in building retention polders the very ex-pensive strengthening of the existing drainage system is no longer necessary. How can they be sustained / enhanced? By increasing the attractiveness for tourism alternative benefits for land owner can be generated.
Multi-functional land use in the catchment and in the retention area How can they be sustained / enhanced? Support farmers with land in the retention area (e.g. financially or with additional agricultural land outside the retention area). Sup-port discussions between farmers’ associations and nature con-servation agencies.

6.8 Faiblesses/ inconvénients/ risques de la Technologie et moyens de les surmonter

Faiblesses/ inconvénients/ risques du point de vue de l’exploitant des terres	Comment peuvent-ils être surmontés?
The retention polders will change the landscape and this may reduce the value of the region for tourism	Include tourist concerns within the retention area (accessibility, information, attractiveness)
Endangered species might lose habitats when building up the retention polders	Do not build a retention area where endangered species live
Loss of livelihoods	Retention areas should be planned for parts of the landscape without settlements

Faiblesses/ inconvénients/ risques du point de vue du compilateur ou d'une autre personne ressource clé	Comment peuvent-ils être surmontés?
Loss of land for agricultural production	Create retention polders where the productivity is already low. Encourage alternative land use (for example reed production) in the retention polders.
High water levels (especially with changing levels) may generate high emissions of greenhouse gases.	Ground water levels should kept stable near to the soil surface.
Retention area is probably too small if pessimistic sea level rise predictions come true.	Increase size of retention polders.

7.1 Méthodes/ sources d'information

7.2 Références des publications disponibles

Titre, auteur, année, ISBN:

http://www.comtess.uni-oldenburg.de/

7.3 Liens vers les informations pertinentes en ligne

Titre/ description:

http://www.comtess.uni-oldenburg.de/