It began to get colder again around 115,000 years ago, marking the beginning of the Devensian glaciation. During this time, ice flowed along the Lincolnshire coast and through the entrance to the Wash and into the Fens. For 100,000 years the Wolds stood above the ice and experienced severe tundra conditions with snow and meltwaters seasonally cutting valleys into rocks that were permanently frozen beneath the surface. Most of the deep, dry valleys and the steep sided open ended gorges, including the River Lud at Hubbards Hills were formed at this time.

Hubbards Hills, Louth’s 40m deep, steep sided chalk valley was originally cut by torrents of glacial meltwater during the last ice age about 40,000 years ago. The ice had dammed up the Hallington Valley to create a lake which spilled over into the Welton Valley as a waterfall. As this was cut back, so Hubbards Hills was formed. Such was the volume of water that this process took two to three hundred years.

Today the river continues to play an important part in the landscape. Chalk streams are one of the most important habitats in Lincolnshire. Springs occur either at the edge of the chalk, where it meets the clay or where the water rises through the chalk along structural weaknesses and at certain times of the year these springs can easily be seen in the meadow near the stepping stones.

Typical chalk streams are shallow and narrow with a gravel bed. The clear mineral rich water is relatively warm and ice free in winter and cool and oxygen rich in the summer, attracting a wide diversity of plants and animals.