Approaches to the problem

Consider in order each of the following approaches and decide which are most relevant to the problem you are trying to solve.

1. Is there an existing drain which is blocked? Many paths were properly drained in the past and can be quickly and sometimes spectacularly improved by locating the old drain, and unblocking it.
2.  Investigate the use which the path receives. Horses or wheeled traffic may be using the path illegally, breaking piped culverts and the edges of open drains, as well as destroying vegetation and soil structure.
3.  It may be easier in the long run to avoid the problem by re-routing the path. The new route must be chosen with care to ensure that it will not develop a similar problem. Re-routing rights of way may involve a diversion order.
4. Design and construct a new drainage system, as described below. Note that a camber or cross-fall to shed water off the path is the simplest form of drainage.
5.  Lay surfacing material on the path. This may be effective either in providing a strong surface which cannot be cut up and eroded when wet, or by actually lifting the level of the path above the water table. See Chapter 8 – Surfacing.
6.  Construct a boardwalk or bridge, which may avoid having to drain an ecologically interesting wet area. See Chapter 9 – Boardwalks and bridges.

Locating old drains

Paths likely to have drains are major routes between villages and settlements, and those showing other signs of construction such as walls, revetments and surfacing.

1. Visit the path in wet weather and find the point where water is running onto the path. Dig around at this point, and you may uncover a culvert opening.
2. Examine ditches alongside paths, especially after rainfall. A disturbance in the water, perhaps with muddy or rusty ochre colouring, can indicate a submerged drain. Staining on the side of the ditch may be a sign of a blocked outfall.
   
3. Look out for signs along the path such as holes in walls which no longer seem to have any function. Large stone slabs may indicate the top of an old culvert. In some areas, the outfalls of drains were traditionally marked by planting a single holly tree in the hedgerow.
   
4. Muddy patches on the path may be the result of sediment dropped by water which previously flowed through a culvert. If scraping away some mud reveals a surfaced layer, there is a good chance of finding a blocked culvert underneath.
   
5. Talk with local farmers and residents who may remember where drains used to function.
6. Look up old maps and records, as these may show drainage systems. Old 6” to the mile maps should be obtainable through the local authority or archives office. Most cultivated land has been drained in the past, and large estates usually had records of any drainage work done.
7. Aerial photographs often reveal evidence of old drainage systems which show up as dark lines. Most areas of the country have been covered, and the local authority should have copies. If not, they are obtainable from commercial aerial photography firms.

Restoring old drains

1. Try to clear piped culverts with drainage rods. Tile drains may well be broken or displaced, in which case the culvert will have to be excavated and a new pipe laid.
2. Other piped drains are more difficult to rod because of their length. Rod as far as possible, and then dig down at that point to try and locate the blockage.
   
   
3. Blocked stone culverts will have to be dismantled and rebuilt. Rocks can easily wedge inside and block the culvert again if the sides are not smooth. It may be easier to install a plastic pipe inside. Build headwalls of stone to protect and hide the ends of the pipe.
4. Dig ditches as necessary at the infall and outfall of the culvert.