Beaver Dam Hydrology — Flood Attenuation & Wetland Formation

Dam Structure

Dam crest height 0.8 m

Beaver dams present

Watershed

Bank / soil permeability 0.50

Storm intensity 1.5×

Live Readouts

Downstream discharge

0.30 m³/s

Wetland water stored

0 m³

Peak flood attenuation

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How it works

Each pond behind a dam obeys a water-balance (continuity) equation — the change in stored volume equals what comes in minus what leaves:

dh/dt = (Q_in − Q_out − Q_seep) / A

Once the pond rises above the dam crest, water spills over as a broad-crested weir; below crest it still trickles through the loose stick-and-mud structure:

Q_weir = Cw·L·(h − h_dam)^1.5   (h > h_dam)
Q_leak = k·h                    (porous dam body)

Water pushed sideways into the banks obeys a Darcy-law-style seepage term set by the permeability slider, and accumulates in an aggregate water-table reservoir that slowly releases back to the channel as baseflow:

Q_seep = K·h
dWT/dt = ΣQ_seep − k_drain·WT
Q_downstream = Q_out(last dam) + k_drain·WT

Dam crest height — taller dams hold back more water before spilling, raising storage capacity.
Beaver dams present — toggled off, inflow passes straight through with no ponding or seepage, so you can compare the hydrograph with and without the cascade.
Soil permeability — controls how fast pond water recharges the surrounding water table (the process that turns a stream reach into a wetland).
Trigger storm event — injects a flood pulse upstream; the peak-attenuation readout compares the pulse's peak inflow against the peak it produces downstream.

Real-world relevance: this is the mechanism behind "beaver dam analogue" restoration — a cascade of small dams slows and stores floodwater, elevates the local water table, and sustains stream baseflow through dry spells, which is exactly how beaver activity converts a simple channel into a wetland.

Pond water Wetland / water table Dam structure

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