Igor Potočnik
University of Ljubljana Biotechnical Faculty Slovenia
University of Zagreb - Faculty of Forestry – 05 May 2015

1. INTRODUCTION
2. CAUSES OF DEGRADATION OF FOREST ROADS
3. DAMAGES OF THE UPPER ROAD LAYER
4. HOW TO ENSURE MAINTENANCE OF FOREST
ROADS
5. MAINTENANCE OF STRUCTURES
ON THE FOREST ROADS
6. BMP AND WMP
7. THE LEVEL OF FUNDING NECESSARY FOR
MAINTAINING FOREST ROADS
8. SUMMARY AND QUESTIONS

1 INTRODUCTION
– Forest roads are necessary for normal forest management and the multi-purpose use of forests,
– They should be regularly maintained to fulfill their role,
– Problem of maintenance, management and planning the forest road network,
– Less expensive and quicker construction of forest roads = higher total costs for construction and maintenance,
– From an economical point of view a forest road is an object of investment,
– Maintenance of forest roads: normal service and profitability.

– Maintenance of forest roads =
+ maintenance of carriageway
+ maintenance of drainage systems
+ maintenance of structures
+ maintenance of embankments.
– The purpose of maintenance is to ensure the regular functioning of the forest road as a whole.

Why is maintenance of forest roads necessary?

How to achieve transportability of forest roads?
Usage
Construction
Transportability of forest roads
Economy
Maintenance

Basic problems: wide extension, inexpensive construction, economic efficiency, limited financial sources

Basic problems: traffic load
Extreme case
Forest road

2 CAUSES OF DEGRADATION OF FOREST ROADS
The main groups of causes of forest road degradation:
– consequence of (improper) planning and construction of forest roads,
– consequence of improper use of forest roads,
– consequence of natural forces.

2.1 Planning and construction of forest roads
FACTORS:
– Natural Conditions: general information on the area being opened up, the economic and environmental situation, etc.
– State of Forests: forest stocks, state of health, biological composition, ownership and the dispersion of forest properties, etc.
– Existing Traffic Communications : how well the forests are opened up with public traffic lines (train, public roads), and main links (primary and secondary) through forests.

Improper planning and construction

Improper planning and construction

Dynamic equilibrium of planned forest road network
INTEGRAL
TRAFIC
SYSTEM
SOCIAL
DEMANDS

Planning process of forest road network
Desired (optimum) situation
F ee dba ck
Realisaton
Selection of variant
Assessment of variants
Variants
Informational support
Prospective plan
Idea, need
F ee dba ck
Initial stage

Three ways of integrating the forest road network into the environment:
– appropriate planning of route,
– designing embankments,
– and biotechnical renovation measures of intervention into the forest.
ESSENTIAL : to treat the forest road network in three dimensions while taking into account forest's time component.
If these principles are considered =
Achieving the least possible disturbance to the forest ecosystem

2.2 Improper use of forest roads
– Is reflected as structural damage of the upper road layer and reconstruction of this is one of the most expensive measures of maintenance.
– Improper use of the forest road comprises:
– transport of overloaded trucks,
– use of a low surfaced forest road after heavy rain or snow melting,
– transport of caterpillar and chain-wheeled tractors,
– logging operations,
– driving over the speed-limit,
– etc.

Improper use of forest roads

Improper use of forest roads – cont.
Improper use

2.3 Impact of natural forces
Water, snow, ice, natural disasters and vegetation
– Water : rainwater trickling, freezing, erosion, draining
– Snow : problem at melting temperature, surface with low bearing capacity, erosion, slush - similar to the impact of rainwater, damage: ground subsiding, site sliding, potholes etc.
– Vegetation : might be an obstacle to proper drainage. Roots in the upper road layer loosen the road structure and allow water to soften the road structure and carriageway.
– Insufficient cleaning of culverts may result in vegetation and roots, contributing to incomplete drainage.

Impact of natural forces

Improper draining, process of degradation

Incomplete drainage due to vegetation

3 DAMAGES OF THE UPPER ROAD LAYER
– Pot-holes: forest roads with longitudinal inclination of between 0 and 3 %.
– Erosion ditches: with no regard to the longitudinal inclination. The role of built-in open top culverts: very effective against erosion on steep terrain with intensive rainfall.
– Damaged carriageway due to water runoff and traffic: as with erosion ditches.

Land sliding (appearance: 8.2%)

Debris accumulation (appearance: 17,0%)

Cart-ruts (appearance: 18.4%)

Pot-holes (appearance: 19.0%)

Damaged embankments (appearance: 20.4%)

Rolling carriageway (appearance: 29.3%)

Erosion (appearance: 34.0%)

Erosion ditches (appearance: 70.1%)

Damaged carriageway (appearance: 84.4%)

Vegetation growing-in (appearance: 84,4%)

Drainage system damages
100%
80%
60%
40%
20%
0%
95,9
1,4
2,7
Cross-ditch
Not damaged
43,5
39,5
17,0
Side-ditch
Damaged
69,4
12,9
17,7
Pipe culvert
Not built

Cross-ditch
Side-ditch
Pipe culvert

Damaged side-ditch

Damaged cross-ditch

Pipe culvert - water inflow

Pipe culvert - water outflow

Pipe culvert – damaged water outflow

Bridge damages

Bridge damages

Bridge damages

4 HOW TO ENSURE MAINTENANCE OF FOREST ROADS
• Three aspects:
– Aspect of time (annually, periodical)
– Aspect of economy (regular, investing)
– Technical aspect (repairing of carriageway, full reconstruction of the upper road layer)
• Use of appropriate technology
• Financial issue (!)

Forest road on soil with low bearing capacity
Geotextile

5 MAINTENANCE OF STRUCTURES ON THE FOREST
ROADS
Landslides: common types of damage to forest roads shown as instability of the road surface due to water softening the base soil and causing it to slide.

Possible actions:
– stone stacks,
– retaining walls,
– reinforced concrete crib revetments,
– stabilization by means of piles,
– timber crib revetments

Timber crib revetments
+
– timber available in the vicinity of the construction site,
– lighter machinery used in construction,
– no extensive preparations required,
– greening of surrounding areas quick and easy,
– the structure is flexible and adapts well to changing ground conditions.
-
– timber gradually decays and loses its bearing qualities;
– the structure is not durable;
– the repair is usually costly;
– suitable for forest roads with low traffic loads;
– not a good solution for forest roads with heavy traffic.

6 BMP AND WMP (Best Management Practice and Worst
Management Practice

7 THE LEVEL OF FUNDING NECESSARY FOR
MAINTAINING FOREST ROADS
7.1 Working method
– Case study of a local community (292 km),
– Random sampling of forest road sections (100 m, 5% sampling),
– Estimation of necessary quantities of material and work to provide their full shape and function,
– Extrapolation sample – forest road network

7.2 Results
– 1% of necessary expense for settlement of the lower road layer,
– 37% of necessary expense for reconstruction of the carriageway and
– 62% of necessary expense for reconstruction of the drainage system.
– 2 – 4 % of construction cost of a forest road is necessary for its maintenance on the annual basis,

WHAT TO DO?
District foresters should play the most important role in planning, controlling and the undertaking of maintenance of forest roads.
We shall set the random sample of forest road sections for permanent monitoring of forest road condition and several influential factors.
Non- forestry use of forest roads – higher standards new financial sources

THANK YOU FOR YOUR ATTENTION

Q and A