Roads and trails on the ridges

Roads and trails on the ridges

Transport infrastructure as part of the watershed

A road or trail along a mountain ridge affects more than just the movement of people and vehicles. It also alters the natural distribution of water, wind, snow, soil, and vegetation between adjacent slopes.

Even a narrow gauge can become an artificial channel, which:

intercepts water;

directs it along the ridge;

transfers runoff from one basin to another;

accelerates erosion;

destroys saddles;

creates the beginning of a ravine;

disrupts the supply of springs;

becomes a path for the spread of fire;

facilitates the penetration of invasive species.

The main principle:

The ridge road should not become a new watershed, dam or canal.

Its purpose is to provide access without disrupting the natural functioning of the mountain system.

1. The particular danger of ridge roads

On a normal slope, water moves predominantly downwards.

On the crest, the situation is more complex: water can be distributed between several catchment areas at once.

If a road changes the surface elevation, creates an embankment or a cut, it may:

hold water on one side;

collect it in a road ditch;

run along the ridge for hundreds of meters;

dump the entire flow into one point;

redirect water to another slope.

As a result, a small road spillway may receive water from an area that would never naturally drain into that location.

2. Main types of ridge routes

2.1. The trail along the watershed line

Such a trail is usually relatively safe given its narrowness and the absence of deep ruts.

Main risks:

soil compaction;

destruction of moss and soil crust;

rutting;

acceleration of flow during a downpour;

widening the route to bypass dirty areas.

For walking routes, a ridge line is often preferable to a steep slope traverse, but only if good load management is in place.

2.2. The road is slightly below the ridge

This type of road intercepts slope runoff.

It can act as a long horizontal ditch and collect water from the upper area.

Risks:

saturation of road cuttings;

collapse of the upper slope;

embankment erosion;

concentrated water release;

formation of a landslide below the road.

2.3. Road through the saddle

A saddle is often a natural transition zone between basins.

The road embankment here may:

block the natural flow;

create a temporary reservoir;

cause overflow through the canvas;

break through during a downpour;

sharply transfer water to the adjacent slope.

Saddles require separate hydrological calculations.

2.4. Serpentine approach to the ridge

The serpentine road repeatedly crosses the slope drainage.

Every turn can become:

water accumulation zone;

breakthrough point;

place of landslide;

the beginning of the erosion channel.

Internal ditches are especially dangerous if they continuously conduct water to the lower bend.

2.5. Technological road

Used for:

reforestation;

construction;

monitoring;

sensor maintenance;

fire safety works.

The main problem with temporary roads is that after the work is completed they are often left without repair.

Such roads must be designed with a plan for subsequent closure, decompaction and return to natural flow.

3. Watershed influence

Each road divides the surface into new micro-catchments.

It can perform one of four undesirable functions:

Barrier

The embankment prevents the natural movement of water.

Interceptor

The internal ditch collects water from the upper slope.

Channel

Ruts and ditches carry water along the road.

Concentrated release

All collected water is discharged through one pipe or a break in the embankment.

The most dangerous combination is all four functions in one road system.

4. Basic design principles

4.1 Minimal intervention

The road should be as narrow as its function allows.

Should be reduced:

width of the canvas;

depth of excavation;

embankment height;

volume of removed soil;

number of intersections of natural channels;

compaction area.

4.2. Maintaining the natural distribution of water

Water should cross the road in approximately the same places and directions where it passed before construction.

It is impossible to collect many small streams into one large release without special calculations.

4.3. Frequent scattering

It is better to organize many small issues than one large one.

This allows:

reduce the volume of each stream;

reduce speed;

maintain distributed moisture;

avoid the formation of a ravine;

reduce damage to the lower slope.

4.4. Self-unloading

The canvas should shed water at short intervals.

The road should not retain water in the ruts or carry it over long distances.

4.5. Safe Failure

Even if a pipe becomes clogged or a ditch collapses, the water must have a safe path.

It is necessary to determine in advance:

where the overflow will occur;

will it wash away the embankment?

will the water flow towards the building?

will the flow hit an unstable slope;

Is the lower section capable of accepting water?

5. Cross-section of the road

5.1. External slope

The canvas is slightly tilted outward to allow water to quickly flow away from the road onto the slope.

Advantages:

lack of a long internal ditch;

uniform dispersion;

less water accumulation;

reducing the risk of flow concentration.

An external slope isn't suitable for all types of slopes. On very steep or unstable slopes, uncontrolled water discharge can cause erosion.

5.2. Internal slope

The water is directed towards the internal ditch.

This profile requires:

frequent water discharges;

stable ditch;

protection against clogging;

regular maintenance;

safe drop points.

A long internal ditch without frequent outlets is extremely dangerous.

5.3. Convex profile

The center of the road is slightly higher than the edges.

Water is discharged in both directions.

This option can be used on the very line of a wide ridge if both slopes are stable and uniform water distribution is acceptable.

6. Drainage elements

Cross drainage systems

Small cross elements drain water from the canvas.

Their task is not to slow down the flow, but to remove it from the road as soon as possible.

Spillway shafts

Low diagonal shafts direct water outward.

They are suitable for:

forest roads;

temporary routes;

low speed roads;

closed technological routes.

Open trays

They are used where the pipe can often become clogged.

Advantages:

visible state;

easy cleaning;

the ability to pass stones and branches.

Culverts

Pipes require care.

Main risks:

clogging;

insufficient diameter;

erosion of the entrance;

outlet erosion;

undermining of the embankment;

overflow across the road.

On dangerous temporary riverbeds, a bridge or a wide open crossing is preferable.

Flow diffusers

At the outlet, the water should not hit unprotected ground.

Used:

rock fill;

stepped tray;

plant filter;

wide grass strip;

small distribution bowl;

several divergent issues.

7. Crossing riverbeds

Any permanent or temporary channel is considered as an independent object.

Before crossing, it is necessary to determine:

catchment area;

peak consumption;

sediment volume;

size of stones to be carried;

probability of tree jam;

traces of old floods;

width of natural spill;

possibility of mudflow.

The main principle:

The road must cross the riverbed, and not force the riverbed to obey the road.

8. Bridges, pipes and fords

Bridge

Preferred where:

there is a permanent watercourse;

large deposits are possible;

there is a risk of tree jam;

the riverbed is actively changing;

severe floods are expected.

The bridge must leave enough space not only for water, but also for rocks, branches and debris.

Tube

Acceptable in a small stable catchment area.

You can't rely solely on normal water flow. Clogging and extreme scenarios must be taken into account.

Fortified ford

Can be used on small seasonal flows with low traffic intensity.

He must:

repeat the natural shape of the riverbed;

do not create a threshold;

withstand erosion;

allow water to pass over the road;

be closed to traffic during flooding.

9. Roads in conditions of abnormal rainfall

For each site, at least four scenarios are considered:

downpour on dry soil;

downpour on wet soil;

repeated downpour on saturated ground;

heavy rain with wind, tree falls and landslides.

During an extreme event the following may occur:

overflow of ditches;

clogging of pipes;

overflow through the canvas;

destruction of the embankment;

formation of a new channel;

mudflow;

blocking the escape route.

Critical roads must have alternative routes or safe waiting areas.

10. Influence of wind

On the ridges, the wind acts directly on the road infrastructure.

He can:

blow out fine soil;

cover the road with snow;

carry sand and dust;

cut down trees;

destroy light fences;

reduce visibility;

increase icing;

carry water to one side of the road.

Therefore, road drainage cannot be assessed solely by vertical rainfall. Slanting rainfall can create uneven loads on slopes and ditches.

11. Snow and icing

The ridge road can become a snow collector.

It gets carried away especially quickly:

deep recesses;

areas behind dense bushes;

saddles;

leeward sides of embankments;

areas behind solid fences.

The snow scheme must take into account:

winter wind directions;

snow cornice zones;

accumulation sites;

spring melting;

rain on snow;

refreezing of water.

Melt water should not flow uncontrollably under the road structure.

12. Slopes and embankments

Upper slope of the excavation

Risks:

shower;

underwash;

saturation;

falling rocks;

soil layer creep.

Necessary:

reduce the height of the slope;

preserve natural vegetation;

arrange for safe interception of water above;

secure individual sections;

Remove unstable stones regularly.

Lower slope of the embankment

Risks:

point water discharge;

erosion of the base;

embankment slip;

formation of a ravine;

weak slope overload.

Embankment must not be placed over organic, saturated or landslide-prone soils without inspection.

13. Working with excavated soil

The soil left after construction cannot simply be dumped down the slope.

Dumps can:

block small channels;

overload the slope;

to be destroyed by rain;

turn into a mudflow;

defoliate.

Extracted material:

used in stable sections of embankment;

is exported;

is located on specially prepared sites;

stabilizes;

becomes green;

protected from runoff.

14. Paths

A walking path can also become a canal.

Particularly dangerous are:

straight climbs along the slope line;

deep ruts;

areas of constant mud bypass;

unmanaged bicycle routes;

horse trails;

contractions between turns.

It's better when the trail:

has a slight transverse slope;

changes direction smoothly;

regularly discharges water;

does not pass through wet pockets;

reinforced in the most heavily loaded areas;

has clear boundaries.

15. Stairs and steps

Steps are useful on short steep sections but can concentrate water.

They must:

skip the side drain;

have a stable foundation;

do not create a long trench;

be secured;

do not direct water straight down.

On natural routes, rare wide steps with scattered areas between them are preferable.

16. Bicycle and horse riding routes

They create a higher load than a typical walking trail.

It is necessary to take into account:

width;

braking areas;

surface destruction;

rut depth;

season of use;

soil moisture;

obstacle avoidance.

Routes should be temporarily closed:

after heavy rains;

during snowmelt;

when the soil is completely saturated;

after the fire;

at the onset of erosive damage.

17. Restriction of movement

On vulnerable ridges the following are used:

seasonal closure;

prohibition of heavy machinery;

Speed ​​Limit;

One Way;

access control system;

traffic ban after heavy rains;

physical blocking of unauthorized exits;

tourist routing.

Restricting access is part of the recovery process, not an administrative formality.

18. Temporary construction roads

A temporary road must have a full life cycle:

design;

minimal construction;

usage;

regular maintenance;

closing;

dismantling drainage if it interferes with nature;

relief restoration;

decompression;

return of vegetation;

post-rainfall monitoring.

Simply leaving an abandoned road means leaving a permanent erosion object.

19. Closing old roads

Unused roads need to be not only closed to traffic.

Conducted:

restoration of natural water flows;

creation of transverse ruptures;

removal of dangerous pipes;

web decompression;

slope stabilization;

partial return of excavated soil;

laying wood and stone;

sowing of local grasses;

planting shrubs;

monitoring.

On steep sections, completely loosening the roadbed can be dangerous. Work is performed in sections.

20. Fire function of roads

The ridge road can serve:

fire-resistant access;

observation line;

evacuation route;

place of equipment turnaround;

partial fire break.

But she can also:

facilitate access for arsonists;

spread sparks;

promote the introduction of invasive grasses;

direct the fire with the wind along the ridge.

Therefore, the fire safety role is assessed together with the environmental damage.

21. Ecological transitions

Roads should not completely cut off ecological corridors.

The following is provided:

areas without fences;

passages for small animals;

safe crossings;

preservation of shrub connections;

limiting night lighting;

reduction in speed;

seasonal restrictions during the breeding season.

22. Road monitoring

After construction the following are controlled:

canvas condition;

rut depth;

ditch work;

condition of pipes;

overflow points;

release blur;

slope movement;

the appearance of cracks;

vegetation condition;

snow accumulation;

tree debris;

spread of invasive species.

Mandatory inspections are carried out:

before the rainy season;

after every extreme rain;

after a strong wind;

then the snow melts;

after the fire;

after an earthquake or landslide.

23. Digital road passport

Each route is included in the Mountain Digital Twin.

The passport contains:

appointment;

category;

width;

type of coating;

longitudinal and transverse slope;

intersected watersheds;

water drainage points;

pipes and bridges;

risk zones;

slopes;

seasonal restrictions;

repair history;

photographs;

examination results;

emergency plan;

responsible operator.

24. Indicators of correct operation

A road is considered hydrologically stable if:

long streams are not formed on the canvas;

water is dispersed regularly and safely;

the releases do not create gullies;

pipes do not become clogged during normal events;

overflow does not destroy the embankment;

there is no transfer of water between pools;

the lower slopes do not receive concentrated runoff;

landslide activity does not increase;

the vegetation nearby is being restored;

The road remains functional after heavy rain.

25. What not to do

On the ridges it is forbidden to:

to build a long road without a hydrological model;

to dig a ditch along the road for a long distance;

dump the entire flow into one point;

use small pipes on mudflow channels;

fill natural depressions;

build high embankments in saddles without overflow;

store soil on the lower slope;

leaving temporary roads without restoration;

allow continuous movement on saturated soil;

direct road water to landslide areas;

consider the road as an object separate from the watershed.

26. Design sequence

Step 1. Determining the need

It is checked whether the road is really needed and whether it can be replaced by a path, a cable car system, a drone, or periodic access.

Step 2. Watershed mapping

Natural water directions and risk zones are determined.

Stage 3. Selecting a route

Preference is given to a route with minimal crossing of riverbeds and unstable slopes.

Stage 4. Hydrological calculation

Normal and extreme flows are determined.

Step 5. Designing a Safe Overflow

The system's behavior in the event of clogging and destruction is tested.

Stage 6. Construction on a small front

Only the area that can be quickly stabilized is opened.

Stage 7. Restoration of damaged surfaces

Soil, vegetation and erosion protection are immediately restored.

Stage 8. Observation

The road's performance is tested after real rains and winds.

The final principle

The road on the ridge is more than just a route. It's an artificial feature of the watershed.

She must:

maintain the natural distribution of water;

do not collect runoff over long distances;

have frequent secure releases;

withstand abnormal downpours;

do not disturb the supply of springs;

do not create landslides and ravines;

take into account snow, wind and fire;

be restored after use is complete.

A good ridge road barely changes the water's path. A poor road turns light precipitation into a concentrated, destructive torrent.