County soil summary
Soil types in Miami-Dade County, Florida
The most widespread soils are Biscayne, Krome and Perrine; the most common drainage class is very poorly drained (36% of the land), and typical topsoil pH is 7.9.
About 627,000 acres of Miami-Dade County lie in multi-county soil survey areas (FL615, FL622, FL623) that the soil survey does not split by county. Those acres, often public forest or desert land, are counted in the Florida totals but not in the figures below.
- Well or moderately well drained
- 11% of land · state 24%
- Typical topsoil pH
- 7.9 moderately alkaline · state 5.3
- Septic fields very limited
- 61% of land · state 87%
- Subject to flooding
- 18% of land, any frequency · state 16%
Most common soils in Miami-Dade County
Share of mapped land
A county is a patchwork of many soils. These 8 cover 73% of the mapped land; 42 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Urban landLand type, not a soil series | 25.6% | — | — |
| Biscayne | 9.8% | Very poorly drained | 7.9 |
| Waters of the Atlantic OceanLand type, not a soil series | 8.3% | — | — |
| Krome | 7.1% | Moderately well drained | 8.0 |
| Perrine | 5.9% | Very poorly drained | 8.0 |
| Shark Valley | 5.8% | Very poorly drained | Not reported |
| Rock outcropLand type, not a soil series | 5.5% | — | — |
| UdorthentsGeneral soil group, not a named series | 5.0% | — | — |
What this means
What the soils in Miami-Dade County mean for gardens, lawns and septic systems
For your garden
Typical topsoil in Miami-Dade County is moderately alkaline: pH 7.9 (most land between 6.5 and 8.0). Acid-loving plants such as blueberries and azaleas struggle without amended beds, and some trees and shrubs show iron chlorosis (yellow leaves with green veins).
Loamy topsoil (loam, silt loam and similar) covers 37% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is marly silt loam (19% of the land).
50% of the land is somewhat poorly to very poorly drained, so soil stays soggy for long spells after rain and in wet seasons. Raised beds, plants that tolerate wet feet, and not working the soil while wet all help.
For your lawn and yard
On 54% of the land, rain soaks in slowly (hydrologic groups C and D, including dual groups that are D until drained). Expect runoff and puddles after heavy rain: core-aerate compacted lawns and keep ground sloping away from foundations.
A seasonal high water table comes within 18 inches of the surface on 43% of the land, often in spring. Basements, sump pumps and lawns in low spots feel it first.
For a septic system
For conventional septic absorption fields, NRCS rates 61% of the land in Miami-Dade County very limited, 0% somewhat limited and 0% not limited (39% not rated, such as urban land, pits or water).
Statewide, 87% of the land is very limited, so Miami-Dade County is less restrictive than typical.
Where the soil is very limited (slow permeability, a high water table, flooding, shallow bedrock or steep slopes), alternative systems such as mound or sand-filter designs are common and cost more.
Flooding is mapped on 18% of the land (<1% occasional, 17% frequent).
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Drainage
How long the soil stays wet
The most common drainage class is very poorly drained (36%). 11% of the land is moderately well drained or better, compared with 24% across Florida.
Show as a table
| Category | Miami-Dade County | Florida |
|---|---|---|
| Excessively drained | 0.0% | 8.3% |
| Somewhat excessively drained | 0.0% | 1.3% |
| Well drained | 2.2% | 7.7% |
| Moderately well drained | 8.7% | 6.3% |
| Somewhat poorly drained | 7.5% | 8.1% |
| Poorly drained | 6.8% | 35.3% |
| Very poorly drained | 35.5% | 26.0% |
| Not rated | 39.3% | 7.1% |
Septic absorption fields
NRCS rating for conventional drain fields
The rating looks at the soil from 24 to 60 inches deep: permeability, depth to a seasonal water table or bedrock, flooding and slope. “Very limited” means at least one feature is unfavorable enough that a conventional field is hard to make work.
Show as a table
| Category | Miami-Dade County | Florida |
|---|---|---|
| Not limited | 0.0% | 0.1% |
| Somewhat limited | 0.0% | 5.3% |
| Very limited | 60.6% | 87.4% |
| Not rated | 39.4% | 7.2% |
Rain, runoff and water table
Hydrologic soil group, flooding, seasonal water table
Hydrologic soil group
How fast rain soaks in when the soil is already wet. Group A soaks in fastest, D slowest.
Show as a table
| Category | Miami-Dade County | Florida |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 5.6% | 22.1% |
| B: moderate infiltration | 0.7% | 3.6% |
| C: slow infiltration | 0.0% | 1.8% |
| D: very slow infiltration (clayey, shallow or wet) | 12.9% | 2.5% |
| A/D: D as is, A if drained | 19.6% | 39.8% |
| B/D: D as is, B if drained | 4.4% | 13.3% |
| C/D: D as is, C if drained | 17.4% | 10.0% |
| Not rated | 39.4% | 6.9% |
Flooding
Show as a table
| Category | Miami-Dade County | Florida |
|---|---|---|
| No flooding | 48.7% | 78.5% |
| Rare or very rare | 0.4% | 1.2% |
| Occasional | 0.1% | 2.0% |
| Frequent or very frequent | 17.2% | 13.1% |
| Not reported | 33.7% | 5.2% |
Seasonal high water table
Show as a table
| Category | Miami-Dade County | Florida |
|---|---|---|
| Within 18 inches at some time of year | 42.5% | 62.3% |
| 18 inches to 3.3 feet | 7.5% | 8.8% |
| Deeper than 3.3 feet or none reported | 16.3% | 24.4% |
| Not reported | 33.7% | 4.5% |
Topsoil pH and texture
First mineral layer of each soil
Typical topsoil pH is 7.9 (moderately alkaline); 80% of rated land falls between 6.5 and 8.0. Median topsoil organic matter is 4%.
Show as a table
| Category | Miami-Dade County | Florida |
|---|---|---|
| Strongly acidic (below 5.5) | 1.8% | 53.6% |
| Moderately to slightly acidic (5.5–6.4) | 2.0% | 19.0% |
| Near neutral (6.5–7.3) | 2.5% | 4.6% |
| Alkaline (7.4 and up) | 37.2% | 3.6% |
| Not reported | 56.5% | 19.2% |
Texture
Show as a table
| Category | Miami-Dade County | Florida |
|---|---|---|
| Sandy | 5.8% | 74.9% |
| Loamy (loam, silt loam and similar) | 36.7% | 5.1% |
| Clayey (40%+ clay) | 0.0% | 0.7% |
| Organic (muck or peat) | 17.9% | 12.4% |
| Not reported (rock, urban land, etc.) | 39.5% | 6.9% |
Sources & data dates
- Source
- USDA NRCS Soil Survey Geographic Database (SSURGO), queried through Soil Data Access. Public domain.
- Data date
- SSURGO as published on November 3, 2026 (most recent survey area update October 26, 2026). NRCS refreshes SSURGO each October.
- Scope
- Miami-Dade County, Florida (FIPS 12086): 665,100 acres of mapped land, 38,200 acres of open water excluded. State comparisons pool all mapped land in Florida.
- Method
- Shares are by mapped land area: each map unit’s acres in the county times each soil component’s percentage. Open water is excluded. Topsoil values use the first mineral horizon of each component. Full methodology.