Area of drainage basin of this river is more than 450 km2. Babolrud is formed from joining of several streams. This river passes from Babol city and it is arrived to Babolsar city.
Babolrud has a river valley pattern in mountainous region, but it is a meandering stream in Caspian beach plain. Index of meander for this river is very high. Gradient for Babolrud is 1.5-2/1000 in Babol city area and it is 0.5/1000 in Babolsar city. Length of Babolrud is about 40 km in beach plain. Local base level (LBL) of Babolrud is about -24 m from the sea level in place of joining to the Caspian Sea (Babolsar).
Babolrud has 2 groups of river terraces:
- H1 (River terraces with down surface level): (height: 1-2.5 m) & (width: 0-150 m)
H1 is as Boundary of active (yearly) flood plain in parts of river and it is as alternative flood plain in many sections (diacritic of active- alternative flood plain from 20-year flood plain).
Materials of H1: fine-grained & unconsolidated alluvial materials
- H2 (River terraces with high surface level): (height: 4-6 m) vegetation on surface of terrace is compact.
Materials of H2: Aeolian deposits (Loess)
Human interference in natural environment of Babolrud:
- Land use of active & alternative flood plains as agronomy lands
- Construction of building in surface of terraces
- Accumulate of structural rubbishes in natural area of river
Characteristic of flood plain for Babolrud:
- Width of flood plain for Babolrud (in Babol city area): 250 m
- Width of active and alternative flood plain: about 200 m
History of flood in Babolrud: Floodwater of Babolrud is observed mainly immersion (Flood risk of Babolrud: 3).
The oldest floods happened in 1355. Also floodwaters of 1375, 1379 & 1384 are from mainly floodwaters of Babolrud.
Vulnerable area in Babolrud lies between 1.8 km of southern Babol city and 800 m of northern Babol.
Protection plans - Engineering structures:
- Construction of concreting walls with height: 4 m in concave parts of bights of river
- Construction of a levee dam in 30 km from south of Babol in order to protection of agronomy lands
Babolrud in Babolsar: Babolsar River cuts Babol- Babolsar coastal road in km: 15. End of Babolrud is a laminar & low gradient stream and it passes from Babolsar city. Gradient for Babolsar River is 15/1000 in Caspian beach plain. Maximum width of Babolsar River is about 50 m.
H1 in around of Babolsar River is development place of Padi soils now. Materials of terraces: Silt, mud & clay
Babolsar city has been affected by floodwater of 1340. Construction of dam in river path (Sular) was effect in mitigation of damages for this flood.