HydroBASINS lev08 watershed · #2080021820
Bassin de la Sée
A watershed (drainage basin) is not a body of water — it is the land area where rainfall converges towards a single river that eventually reaches the sea (or an endorheic basin). Boundaries follow ridgelines.
Crosses 2 administrative regions : Calvados, Manche
Sub-basin area
468,7km²
Upstream area
468,8km²
Discharge
12,47m³/s
Mean elev.
144m
Administrative coverage
2 dept-equivalent regions (GADM L2)
- 463.4 km²98.6% of basin
- 6.7 km²1.4% of basin
73 communes (GADM L5)Available for FRA, RWA
- Sourdeval34.63 km²93% commune
- Brécey21.57 km²100% commune
- Tirepied19.26 km²100% commune
- Reffuveille15.55 km²65% commune
- Saint-Laurent-de-Cuves14.81 km²100% commune
- Coulouvray-Boisbenâtre13.45 km²76% commune
- Saint-Michel-de-Montjoie12.65 km²87% commune
- Saint-Martin-le-Bouillant12.45 km²99% commune
- Lolif12.30 km²100% commune
- La Chaise-Baudouin12.19 km²100% commune
- Le Grand-Celland11.67 km²91% commune
- Chérencé-le-Roussel11.62 km²100% commune
- Le Mesnil-Tôve11.09 km²98% commune
- Vengeons10.46 km²65% commune
- Les Cresnays9.73 km²100% commune
- Cuves9.49 km²100% commune
- Beauficel9.41 km²100% commune
- Perriers-en-Beauficel9.17 km²100% commune
- Le Luot9.11 km²100% commune
- Saint-Jean-de-la-Haize8.89 km²100% commune
- Plomb8.19 km²100% commune
- Saint-Senier-sous-Avranches8.09 km²92% commune
- Le Mesnil-Gilbert7.88 km²100% commune
- Subligny7.72 km²100% commune
- Saint-Pois7.51 km²100% commune
- Bacilly7.10 km²44% commune
- Marcey-les-Grèves6.96 km²100% commune
- Le Mesnil-Adelée6.82 km²100% commune
- Le Petit-Celland6.81 km²98% commune
- Ponts6.53 km²100% commune
- Sainte-Pience6.48 km²78% commune
- Braffais5.93 km²100% commune
- Vernix5.89 km²100% commune
- Les Loges-sur-Brécey5.64 km²100% commune
- Saint-Georges-de-Livoye5.63 km²100% commune
- Saint-Clément-Rancoudray4.86 km²15% commune
- Le Val-Saint-Père4.81 km²32% commune
- Saint-Barthélemy4.74 km²72% commune
- Avranches4.37 km²97% commune
- Chérencé-le-Héron4.32 km²45% commune
- Juvigny-le-Tertre4.08 km²53% commune
- Bellefontaine3.92 km²53% commune
- Les Chambres3.91 km²91% commune
- La Gohannière3.90 km²100% commune
- Chaulieu3.78 km²35% commune
- Chavoy3.71 km²100% commune
- La Godefroy3.63 km²100% commune
- Notre-Dame-de-Livoye3.61 km²100% commune
- Saint-Nicolas-des-Bois3.57 km²100% commune
- Champ-du-Boult3.57 km²25% commune
- Saint-Jean-du-Corail-des-Bois3.55 km²99% commune
- Lingeard3.51 km²100% commune
- La Chapelle-Cécelin3.41 km²67% commune
- Brouains3.41 km²100% commune
- Saint-Ovin3.34 km²26% commune
- Le Gast3.10 km²24% commune
- Vains2.95 km²24% commune
- La Mouche2.37 km²57% commune
- Gathemo2.29 km²23% commune
- Saint-Brice2.26 km²100% commune
- La Trinité2.08 km²23% commune
- Montviron1.94 km²30% commune
- Le Tanu0.72 km²7% commune
- Le Fresne-Poret0.60 km²6% commune
- Saint-Martin-des-Champs0.37 km²5% commune
- Sainte-Cécile0.21 km²2% commune
- La Lucerne-d'Outremer0.15 km²1% commune
- Le Mesnil-Rainfray0.10 km²1% commune
- Bourguenolles0.10 km²1% commune
- La Chapelle-Urée0.09 km²2% commune
- Boisyvon0.03 km²1% commune
- Ger0.02 km²0% commune
- Champcervon0.00 km²0% commune
7 intersecting protected areas
Vallée de la Sée
IUCN Not ReportedSpecial Areas of Conservation (Habitats Directive)
14.23 km² overlap
Baie du Mont Saint-Michel
IUCN Not ReportedWetland of International Importance (Ramsar Site)
4.52 km² overlap
Baie du Mont Saint-Michel
IUCN Not ReportedSpecial Protection Area (Birds Directive)
2.99 km² overlap
Baie du Mont Saint-Michel
IUCN Not ReportedSpecial Areas of Conservation (Habitats Directive)
1.99 km² overlap
Pres de l\'hopital
IUCN IVLand acquired by Conservatoire du Littoral (national seaside and lakeside conservancy)
0.15 km² overlap
Normandie-Maine
IUCN VRegional Nature Park
0.02 km² overlap
La Sienne Et Ses Affluents
IUCN IVBiotope Protection Order
0.01 km² overlap
Computed live · GADM 4.1 × HydroBASINS lev08 × WDPA · cached after first hit.
Species present
2 709 distinct species · 278 764 observations
Source: GBIF Occurrence snapshot 2026-05-01.
Ecological tissue
Sample of 35 species (selected proportionally per kingdom among those with at least one documented interaction here) to keep the graph readable. Hover for details, click to explore the full ecosystem of a species.
ℹ️ The territory contains many more species than displayed and all their documented interactions: the graph is intentionally the structural skeleton (top-N species by composite local score, edges filtered by Serrano 2009 disparity filter α=0.2).
Indicateurs du tissu écologique
Tissu écologique de Bassin de la Sée : 11 espèces reliées par 169 interactions GloBI sur 6 types (connectance 13.8%, filtre Serrano α=0.2). 39 bulles taxonomiques (cascade genre/famille GloBI, ≥3 espèces).
Comparaison sur la connectance du réseau local complet vs distribution nationale (toutes les communes françaises).
Hydroclimate (BasinATLAS lev08)
Mean T°
10,6°C
Annual rain
780mm
Moisture idx (CMI)
0,05
Runoff
751mm/an
PET
742mm
AET
557mm
Mean slope
3,5°
Water table
197cm
Forest
0%
Crops
9%
Urban
2%
Protected
0%
HydroATLAS BasinATLAS v10 (Linke et al. 2019) · HydroBASINS lev08 (Lehner & Grill 2013)