Technologies

Peak flow control structures (leaky woody dams) [Hungary]

Creation: 03/29/2022 4:12 p.m.
Update: 04/24/2023 9:27 a.m.
Compiler: Brigitta Szabó
Editors: Piroska Kassai, Zoltan Toth, Klara Kerpely
Reviewers: William Critchley, Rima Mekdaschi Studer

Lefolyás-szabályozó létesítmények (szivárgó rönkgátak)

technologies_6201 - Hungary

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Completeness: 94%

1. General information

1.2 Contact details of resource persons and institutions involved in the assessment and documentation of the Technology

Key resource person(s)

co-compiler:

Klara Kerpely

Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)

OPtimal strategies to retAIN and re-use water and nutrients in small agricultural catchments across different soil-climatic regions in Europe (OPTAIN)

Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)

Municipalities as integrators and coordinators in adaptation to climate change (LIFE-MICACC)

Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)

Institute for Soil Sciences, Centre for Agricultural Research (ATK TAKI) - Hungary

Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)

World Wide Fund for Nature Hungary Foundation (WWF Hungary) - Hungary

1.3 Conditions regarding the use of data documented through WOCAT

The compiler and key resource person(s) accept the conditions regarding the use of data documented through WOCAT:

Yes

1.4 Declaration on sustainability of the described Technology

Is the Technology described here problematic with regard to land degradation, so that it cannot be declared a sustainable land management technology?

2. Description of the SLM Technology

2.1 Short description of the Technology

Definition of the Technology:

Peak flow control structures are designed to reduce flow velocities and quantities running down from catchment areas. Leaky dams are peak flow control structures that are made of wood and allow low flows to pass through, but hold back high flows, thus providing temporary storage and enhanced infiltration of flood water.

2.2 Detailed description of the Technology

Description:

Peak flow control structures are designed to reduce flow velocities and quantities of water running down from catchment areas. Leaky dams are peak flow control structures that are made from wood and allow low flows to pass through, but hold back high flows, thus providing temporary storage and enhanced infiltartion of flood water. The structures are elevated 30 cm above streambed level to allow baseflow (and fish) to pass through. The technology is usually applied in hilly areas covered by forest. Woody check dams are made from whole tree trunks sourced locally, placed across the watercourse and secured into place with stakes and wire on both sides of the bank. The purpose is to control sediment and to slow flow velocities and quantities of water running down from catchment areas, in order to reduce flood peaks. The impact of the technology is to retain sediment and water in the upstream part of the catchment to reduce the size of flood peaks, this way avoiding flash floods downstream. The cost of installation and ongoing maintenance is low. However, leaky dams need to be cleared of debris and sediment occasionally so that water can still flow through the gaps. This reduces the likelihood of water flowing over the top of the barrier. The approximate lifetime of a leaky woody dam is about ten years, depending on the tree species used.

2.3 Photos of the Technology

Media Gallery

2.4 Videos of the Technology

Comments, short description:

https://youtu.be/1TnzpVUoDUc
6-min video on the application of leaky woody dams and other water retention measures in Püspökszilágy village.

Location:

Püspökszilágy

Name of videographer:

Filmever Studio

2.5 Country/ region/ locations where the Technology has been applied and which are covered by this assessment

Country:

Hungary

Region/ State/ Province:

Pest County

Further specification of location:

Püspökszilágy

Specify the spread of the Technology:

applied at specific points/ concentrated on a small area

Is/are the technology site(s) located in a permanently protected area?

2.6 Date of implementation

Indicate year of implementation:

2020

2.7 Introduction of the Technology

Specify how the Technology was introduced:

during experiments/ research
through projects/ external interventions

3. Classification of the SLM Technology

3.1 Main purpose(s) of the Technology

reduce, prevent, restore land degradation
protect a watershed/ downstream areas – in combination with other Technologies
reduce risk of disasters
adapt to climate change/ extremes and its impacts

3.2 Current land use type(s) where the Technology is applied

Land use mixed within the same land unit:

Forest/ woodlands

(Semi-)natural forests/ woodlands

(Semi-)natural forests/ woodlands: Specify management type:

Dead wood/ prunings removal

Type of (semi-)natural forest:

temperate continental forest natural vegetation

Are the trees specified above deciduous or evergreen?

deciduous

Products and services:

Nature conservation/ protection
Recreation/ tourism
Protection against natural hazards

Waterways, waterbodies, wetlands

Drainage lines, waterways

gullies

3.3 Has land use changed due to the implementation of the Technology?

Has land use changed due to the implementation of the Technology?

No (Continue with question 3.4)

3.4 Water supply

Water supply for the land on which the Technology is applied:

rainfed

3.5 SLM group to which the Technology belongs

cross-slope measure
surface water management (spring, river, lakes, sea)
ecosystem-based disaster risk reduction

3.6 SLM measures comprising the Technology

structural measures

S5: Dams, pans, ponds
S6: Walls, barriers, palisades, fences

3.7 Main types of land degradation addressed by the Technology

soil erosion by water

Wt: loss of topsoil/ surface erosion
Wg: gully erosion/ gullying
Wo: offsite degradation effects

3.8 Prevention, reduction, or restoration of land degradation

Specify the goal of the Technology with regard to land degradation:

prevent land degradation
reduce land degradation

4. Technical specifications, implementation activities, inputs, and costs

4.1 Technical drawing of the Technology

Technical specifications (related to technical drawing):

There are a few key rules to follow when installing any leaky dams:
1. They must be installed, as a minimum, in a sequence of 3.
2. The distance between each dam should be 7 times channel width.
3. The width of the dam should be 1.5 times channel width.
4. The structure should be set 300mm above base flow level.
5. Logs should be no more than 400mm in diameter.
6. Where possible, materials should be sourced locally.
7. Structures should be installed 90° to the flow.
Other recommendations for design:
- Use to obstruct flows within watercourses or along runoff pathways, gullies, valleys.
- Use in small watercourses less than 3 m wide.
- Height of a barrier should not exceed 1 m.

Author:

source: https://www.ydrt.org.uk/wp-content/uploads/2021/04/NFM-Leaky-Dams-guide.pdf and https://www.ciria.org/ItemDetail?iProductCode=C802F&Category=FREEPUBS&WebsiteKey=a054c7b1-c241-4dd4-9ec1-38afd4a55683

4.2 General information regarding the calculation of inputs and costs

Specify how costs and inputs were calculated:

per Technology unit

Specify unit:

a single structure at multiple points in a watershed

Specify currency used for cost calculations:

4.3 Establishment activities

	Activity	Timing (season)
1.	Installing	Possible in any season. (Logging preferably out of vegetation season.)

4.4 Costs and inputs needed for establishment

	Specify input	Unit	Quantity	Costs per Unit	Total costs per input	% of costs borne by land users
Labour	Installing (team work)	person-days	4.0	50.0	200.0	100.0
Equipment	Machinery for installing (e.g. chainsaw, posthole digger, small excavator) rental cost	1	1.0	200.0	200.0	100.0
Plant material	No explicit cost, locally sourced wood can be used
Construction material	Fastening device kit (e.g. metal wire, poles, clamps)	1	1.0	200.0	200.0	100.0
Total costs for establishment of the Technology					600.0
Total costs for establishment of the Technology in USD					600.0

4.5 Maintenance/ recurrent activities

	Activity	Timing/ frequency
1.	Checking conditions of the structure	yearly or after extreme rain events
2.	Cleaning of debris and sediment	if silting up starts
3.	Fixing or replacing logs	if moved by flood

4.6 Costs and inputs needed for maintenance/ recurrent activities (per year)

	Specify input	Unit	Quantity	Costs per Unit	Total costs per input	% of costs borne by land users
Labour	Checking status and cleaning of debris and sediment	person-days	1.0	50.0	50.0	100.0
Labour	Fixing or replacing logs, if necessary	person-days	1.0	50.0	50.0	100.0
Equipment	Machinery rental, if necessary	1	1.0	100.0	100.0
Total costs for maintenance of the Technology					200.0
Total costs for maintenance of the Technology in USD					200.0

Comments:

Permit required on permanent watercourses. Average lifetime of a dam is about 10 years

4.7 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

Width of the water course.
Availability of locally sourced wood logs.
Availablility of equipment.
Labour costs.
Procurement rules applicable to project owner.

5. Natural and human environment

5.1 Climate

Annual rainfall

< 250 mm
251-500 mm
501-750 mm
751-1,000 mm
1,001-1,500 mm
1,501-2,000 mm
2,001-3,000 mm
3,001-4,000 mm
> 4,000 mm

Specify average annual rainfall (if known), in mm:

550.00

Specifications/ comments on rainfall:

Dry periods are becoming longer and heavy rainevents more frequent due to climate change.

Indicate the name of the reference meteorological station considered:

Püspökszilágy

Agro-climatic zone

sub-humid

Temperate climate, four seasons, mean annual temperature: 10 degrees C

5.2 Topography

Slopes on average:

flat (0-2%)
gentle (3-5%)
moderate (6-10%)
rolling (11-15%)
hilly (16-30%)
steep (31-60%)
very steep (>60%)

Landforms:

plateau/plains
ridges
mountain slopes
hill slopes
footslopes
valley floors

Altitudinal zone:

0-100 m a.s.l.
101-500 m a.s.l.
501-1,000 m a.s.l.
1,001-1,500 m a.s.l.
1,501-2,000 m a.s.l.
2,001-2,500 m a.s.l.
2,501-3,000 m a.s.l.
3,001-4,000 m a.s.l.
> 4,000 m a.s.l.

Indicate if the Technology is specifically applied in:

concave situations

5.3 Soils

Soil depth on average:

very shallow (0-20 cm)
shallow (21-50 cm)
moderately deep (51-80 cm)
deep (81-120 cm)
very deep (> 120 cm)

Soil texture (topsoil):

medium (loamy, silty)

Soil texture (> 20 cm below surface):

medium (loamy, silty)

Topsoil organic matter:

high (>3%)

5.4 Water availability and quality

Ground water table:

< 5 m

Availability of surface water:

medium

Water quality (untreated):

poor drinking water (treatment required)

Water quality refers to:

surface water

Is water salinity a problem?

Is flooding of the area occurring?

Yes

5.5 Biodiversity

Species diversity:

medium

Habitat diversity:

medium

5.6 Characteristics of land users applying the Technology

Sedentary or nomadic:

Sedentary

Market orientation of production system:

commercial/ market

Relative level of wealth:

average

Individuals or groups:

groups/ community

Level of mechanization:

mechanized/ motorized

Gender:

women
men

Indicate other relevant characteristics of the land users:

The technology is applied by the municipality (local government).

5.7 Average area of land used by land users applying the Technology

< 0.5 ha
0.5-1 ha
1-2 ha
2-5 ha
5-15 ha
15-50 ha
50-100 ha
100-500 ha
500-1,000 ha
1,000-10,000 ha
> 10,000 ha

Comments:

The technology is applied by the municipality (local government).

5.8 Land ownership, land use rights, and water use rights

Land ownership:

communal/ village

Land use rights:

communal (organized)

Water use rights:

communal (organized)

Are land use rights based on a traditional legal system?

Yes

5.9 Access to services and infrastructure

health:

poor
moderate
good

education:

poor
moderate
good

technical assistance:

poor
moderate
good

employment (e.g. off-farm):

poor
moderate
good

markets:

poor
moderate
good

energy:

poor
moderate
good

roads and transport:

poor
moderate
good

drinking water and sanitation:

poor
moderate
good

financial services:

poor
moderate
good

6. Impacts and concluding statements

6.1 On-site impacts the Technology has shown

Ecological impacts

Water cycle/ runoff

harvesting/ collection of water

reduced

improved

Comments/ specify:

The main purpose of this measure is slowing the movement of water during high flow events, but temporally it collect water as well providing watering place for wild animals.

surface runoff

increased

decreased

Comments/ specify:

This measure usually takes place in forests (in the upper zone of the watershed), but it has a positive effect on the lower area (agricultural fields) of the watershed by preventing surface runoff and reducing flood events

Climate and disaster risk reduction

flood impacts

increased

decreased

Comments/ specify:

One of the main positive effect of this measure is decreasing flash flood events and its impact both on inhabited area. Since the installation no inundation has happened. However, it may be the result of a combination of different measures.

6.2 Off-site impacts the Technology has shown

reliable and stable stream flows in dry season

reduced

increased

downstream flooding

increased

reduced

Comments/ specify:

damage on neighbours' fields

increased

reduced

Comments/ specify:

The measure is a very effective solution to avoid flood damage.

damage on public/ private infrastructure

increased

reduced

Comments/ specify:

The measure is a very effective solution to avoid flood damage.

6.3 Exposure and sensitivity of the Technology to gradual climate change and climate-related extremes/ disasters (as perceived by land users)

Climate-related extremes (disasters)

Climatological disasters

	How does the Technology cope with it?
forest fire	not well

Hydrological disasters

	How does the Technology cope with it?
landslide	not well

6.4 Cost-benefit analysis

How do the benefits compare with the establishment costs (from land users’ perspective)?

Short-term returns:

positive

Long-term returns:

positive

How do the benefits compare with the maintenance/ recurrent costs (from land users' perspective)?

Short-term returns:

positive

Long-term returns:

positive

6.5 Adoption of the Technology

single cases/ experimental

If available, quantify (no. of households and/ or area covered):

The presented measure (in Püspökszilágy) is one of the study sites of the LIFE-MICACC project

Of all those who have adopted the Technology, how many did so spontaneously, i.e. without receiving any material incentives/ payments?

0-10%

Comments:

The installation costs of the measure was financed by a LIFE grant from the European Union with national co-financing.

6.6 Adaptation

Has the Technology been modified recently to adapt to changing conditions?

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the land user’s view
Slow release of water into surrounding area (agricultural fileds)
Efficient temporary storage of water
Prevention of soil erosion

Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
Prevention of flooding: protection of the infrastructure of the surrouanding settlements
Positive effect on biodiversity: rooting habitat, place of nesting birds, areas of growth for microbes, algae and fungi available water for wildlife
Stabilisation of river banks

6.8 Weaknesses/ disadvantages/ risks of the Technology and ways of overcoming them

Weaknesses/ disadvantages/ risks in the land user’s view	How can they be overcome?
No negative effects are known

Weaknesses/ disadvantages/ risks in the compiler’s or other key resource person’s view	How can they be overcome?
The lifetime of a dam is limited (~10 years)

7. References and links

Links and modules

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