River morphology: A deficit of suspended bed-material load in flowing water will most likely cause the river to become of which type?

Introduction / Context:
Alluvial rivers adjust their bed and planform to the balance between sediment supply and transport capacity. When sediment supply is insufficient relative to transport capacity, the bed tends to lower (degrade).

Given Data / Assumptions:

• Sediment deficit relative to carrying capacity.
• Unarmored or weakly armored alluvial bed.
• Hydraulic conditions otherwise unchanged.

Concept / Approach:
With limited incoming bed material, the flow entrains material from the bed to satisfy transport capacity, producing net erosion. Conversely, sediment surplus leads to aggradation. Planform (e.g., meandering) is influenced by many factors, but sediment balance strongly dictates bed level trends.

Step-by-Step Solution:
Identify imbalance: transport capacity > sediment supply.Flow scours the bed to make up the deficit.Outcome: bed level lowers → degrading reach.

Verification / Alternative check:
Field evidence after sediment-trapping dams shows downstream degradation due to sediment-starved flows; grade-control structures are used to limit incision.

Why Other Options Are Wrong:

• Aggrading type: Requires sediment surplus, opposite condition.
• Meandering type: Describes planform, not necessarily bed level trend caused purely by deficit.
• Sub-critical type: Refers to flow regime (Froude number), not sediment balance.

Common Pitfalls:
Confusing planform descriptors with bed level trends; ignoring that both suspended and bed loads contribute to morphodynamics.

Final Answer:
Degrading type (bed level lowering)