Why this Catchment?

Over view

Why this Catchment?

The micro-catchment was selected in the GIS modelling step because it contains a large number of properties in Honiton that are

potentially at flood risk. The map below shows which buildings overlap with the EA’s modelled “Flood Zone 2” area, specifically areas at risk of flooding from rivers, as identified during the micro-catchment mapping process.

There are 108 buildings potentially at risk out of 1369 in the catchment, approximately 7.89% of them. The catchment’s size of 8.08km2 gives an area of 0.07km2 per building at risk.

The water framework directive (WFD) status in the wider Middle River Otter catchment is Poor

If property owners are willing to work with land owners and vice versa, then small-scale NFM measures upstream in the catchment have the potential to benefit a large number of properties and improve water quality.

Micro-catchment Over view

Topography

The micro-catchment covers the south of the urban area of the town of Honiton in the north as well as several farms, and is intersected in Honiton by the High Street and the railway line. The micro-catchment forms the watershed for the The Gissage, and its tributary the Glen Brook, that flows northwards through the catchment and Honiton where it eventually joins the main River Otter on the north side of the A30 dual carriageway just outside of the catchment outlet. The total river length present in the catchment is approximately 21.6km. Overall, the micro-catchment falls within the Honiton County Parish and is administered by Honiton Town Council.

The map on the right shows the steepness of slopes. The Gissage runs along the bottom of a valley surrounded on 3 sides by a plateau, separated by considerably steep slopes. Honiton sits in the narrowing end of the valley.

Micro-catchment Over view

Land Cover

The way the land is used has significant impacts on flood management. Land use has been mapped here using the Centre for Ecology and Hydrology’s (CEH) Land Cover Map 2019. This is a model derived from satellite imagery at 25m resolution. The land use here is primarily improved grassland, accounting for 43% of the catchment, followed by the urban area of Honiton that covers another 18%.

Patches of broadleaved woodland are spread throughout the catchment and are either adjacent to a watercourse or on top of the plateau around the catchment edges. A coniferous woodland is present on the plateau to the southeast.

Multiple fields of neutral grassland can be find on the eastern side of The Gissage, while 2 large areas of heather can be found on the plateau to the west and southwest. Aside from one large area between these 2 heather areas, arable and horticultural land is sparse and fragmented, covering only 8% of the catchment.

It should be noted that this land cover map model is not a perfect representation of land use as it simplifies UK land cover into very broad classes.

Micro-catchment Over view

Land Cover

Land use observed during the catchment walkover mostly matched the land use mapped here using the Centre for Ecology and Hydrology’s (CEH) Land Cover Map 2019 above.

The ground appeared to be wet in places and of lower agricultural value; particularly in the valley bottom.

Most slopes were pasture with the occasional small field or area given to maize or corn to support dairy farming.

Pockets of tree and woodland were interspersed throughout, some of the hedgerows now supporting corridors of mature trees. Headwater section looking South across the Gissage valley

Mid-catchment pasture with band of maize on hilltop in the Gissage valley