U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2020–1010

Repurposing a Hindcast Simulation of the 1926 Great Miami 

Hurricane, South Florida

EVERGLADES

NATIONAL PARK

Miami

Florida Bay

A

B

C

A

B

C

Biscayne Bay

Repurposing a Hindcast Simulation of the 

1926 Great Miami Hurricane, South Florida

By M. Dennis Krohn, Eric D. Swain, Catherine A. Langtimm, and 

Jayantha Obeysekera

Open-File Report 2020–1010

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DAVID BERNHARDT, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2020

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Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

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Suggested citation:

Krohn, M.D., Swain, E.D., Langtimm, C.A., and Obeysekera, J., 2020, Repurposing a hindcast simulation of the 1926 

Great Miami Hurricane, south Florida: U.S. Geological Survey Open-File Report 2020–1010, 9 p., https://doi.org/

10.3133/ofr20201010.

Associated data for this publication:

Swain, E.D., 2020, FTLOADDS (combined SWIFT2D surface-water model and SEAWAT groundwater model) simulator 

used to repurpose a hindcast simulation of the 1926 Great Miami Hurricane using the south Florida peninsula for 

the Biscayne and Southern Everglades Coastal Transport (BISECT) model: U.S. Geological Survey data release, 

https://doi.org/10.5066/P9C681IV.

ISSN 2331-1258 (online)
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Methods...........................................................................................................................................................3

Previous Simulations ............................................................................................................................3

Comparisons of Storm Effects in Different Simulation Periods ....................................................3

Results .............................................................................................................................................................4

Discussion.......................................................................................................................................................6

Model Limitations..................................................................................................................................6

Summary..........................................................................................................................................................7

Acknowledgments.........................................................................................................................................8

References......................................................................................................................................................8

Figures

1. Map showing the study area including Everglades National Park, Ten Thousand 

Islands, and the eastern coastal area .......................................................................................2

2. Map showing the canal system and topography in the BISECT model area in 

1926 and 1996, south Florida .......................................................................................................4

3. Maps showing salinity and inundation in areas A, B, and C before and after 

the hindcast inland system and hindcast sea-level simulation; recent inland 

system and recent sea-level simulation; and hindcast inland system and recent 

sea-level simulation, south Florida ............................................................................................5

4. Graphs showing inundation and salinity before and after the simulated Great 

Miami Hurricane of 1926, south Florida ....................................................................................7

Table

1. Changes in inundation and salinity in three areas before and after the 

simulated Great Miami Hurricane of 1926, south Florida .......................................................6

Conversion Factors

International System of Units to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

Area

square meter (m2) 0.0002471 acre

square kilometer (km2) 247.1 acre
iv

Datum

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Elevation, as used in this report, refers to distance above the vertical datum.

Abbreviations

BISECT Biscayne and Southern Everglades Coastal Transport

CERP Comprehensive Everglades Restoration Plan

ET Evapotranspiration

FTLOADDS Flow and Transport in a Linked Overland/Aquifer Density-Dependent System

GMH Great Miami Hurricane

HH Hindcast hydrology and hindcast sea level

HR Hindcast hydrology and recent sea level

PSU Practical salinity units

RR Recent hydrology and recent sea level

SLR Sea-level rise

TIME Tides and Inflows in the Mangroves of the Everglades

TTI Ten Thousand Islands

USGS U.S. Geological Survey
Repurposing a Hindcast Simulation of the 1926 Great 

Miami Hurricane, South Florida

By M. Dennis Krohn,1 Eric D. Swain,1 Catherine A. Langtimm,1 and Jayantha Obeysekera2

1U.S. Geological Survey.

2Florida International University.

Abstract

Hydrodynamic model hindcasts of the surface water 

and groundwater of the Everglades and the greater Miami, 

Florida, area were used to simulate hydrology using estimated 

storm surge height, wind field, and rainfall for the Great 

Miami Hurricane (GMH), which struck on September 18, 

1926. Ranked estimates of losses from hurricanes in inflationadjusted dollars indicate that the GMH was one of the most 

damaging tropical cyclones to make landfall in the United 

States, but little hydrologic data were collected because 

many types of field stations did not exist at the time. Several 

techniques were used to estimate previously unknown critical 

storm variables for model input, demonstrating the value of 

reanalyzing historical storm events using modern hydrodynamic modeling. This representation of the 1926 GMH was 

then used to develop a hypothetical simulation of the hydrologic effects of a similar hurricane occurring in contemporary 

(1996) times. Results indicate that the 18-centimeter sea-level 

rise between 1926 and 1996 had a greater effect on salinity intrusion than climatic differences or the development of 

modern canal-based infrastructure. Moreover, the post-1926 

canal infrastructure does not seem to substantially mitigate the 

deleterious effects of sea-level rise.

Introduction

The U.S. Geological Survey (USGS) has developed 

a coupled hydrodynamic surface-water and groundwater 

simulator to improve understanding of the complex and 

interconnected hydrology in south Florida. This simulator, 

which is a combination of a pre-existing two-dimensional 

hydrodynamic surface-water code and a three-dimensional 

groundwater code, both with salinity transport (Langevin and 

others, 2005), is referred to as Flow and Transport in a Linked 

Overland/Aquifer Density-Dependent System (FTLOADDS). 

FTLOADDS provides a tool to examine the important surfacewater, groundwater, and coastal saline-water interactions 

prevalent in south Florida.

FTLOADDS has been applied to locations in Everglades 

National Park (Wang and others, 2007), Ten Thousand Islands 

(Swain and Decker, 2009), and the Biscayne Bay coastal urban 

area (Lohmann and others, 2012; fig. 1). The hydrologic conditions simulated by these models have been used in numerous 

ecologic models and analyses (Stith and others, 2011; Green 

and others, 2014; Zajac and others, 2015). The applications 

to Everglades National Park and the Biscayne Bay coastal 

area were combined to produce the Biscayne and Southern 

Everglades Coastal Transport (BISECT) model (Swain and 

others, 2019), which includes the southern tip of the Florida 

peninsula. BISECT is being used to examine the dynamics of 

sea-level rise for the Comprehensive Everglades Restoration 

Plan (CERP) water-management changes and other structural 

changes to the hydrodynamic system.

Appraisal of the effects of future climate change on 

the hydrologic system in south Florida requires projection 

of future climate and sea-level conditions. The uncertainty 

in projecting future conditions requires the examination of 

multiple scenarios and a determination of the sensitivity of 

the hydrologic system to these uncertainties (Obeysekera and 

others, 2015). An examination of past conditions and how they 

compare to recent hydrology also helps to develop an understanding of the dynamics of the system and how hydrology 

responds to sea level and management changes. In order to use 

the BISECT model to examine hydrologic factors that affect 

coastal vegetation change, a hindcast simulation was developed for conditions during the 1926–1932 period (Swain and 

others, 2015). These results can be compared to the results of 

the 1996–2004 simulation to determine the effective differences in coastal vegetation habitat factors. The hindcast simulation includes the Great Miami Hurricane of 1926 (GMH), a 

major storm that ranks as the costliest hurricane in the United 

States when normalized to inflation and wealth at the national 

level and changes in population and housing at the coastal 

county level (Pielke and others, 2008). The characteristics 

of the GMH must be largely estimated due to lack of historical data, which was also the case for much of the input to the 

1926–1932 simulation.
2 Repurposing a Hindcast Simulation of the 1926 Great Miami Hurricane, South Florida

The hindcast model allowed the long-term effects of 

the GMH to be examined by incorporating additional scenarios where the effect of the hurricane was removed from 

the simulation (Swain and others, 2015). The effect of the 

storm depends on the antecedent hydrologic conditions and 

the physical features relevant to the coastal surge. Comparing 

the same storm strike at different historical times can improve 

understanding of how changes in the system can affect the 

severity of storm damage.

The purpose of this report is to use numerical simulations of the hydrologic response to historical and hypothesized 

modern hurricane strikes to determine how historical changes 

in climate, sea level, coastal topography, and the manmade 

canal system affect the severity of inundation and salinity 

intrusion from a major storm. Determining the hypothetical 

effects of a storm at different points in time is made possible 

by using numerical hydrologic simulations. An assessment of 

those effects can determine which historical changes affect the 

hydrologic response to a particular storm.

Gulf of Mexico

EVERGLADES NATIONAL PARK

Miami

Florida Bay

Study area

FLORIDA

400000 420000 440000 460000 480000 500000 520000 540000 560000 580000

UTM easting, in meters

UTM northing, in meters

2820000

2800000

2780000

2760000

2740000

2720000

2840000

2860000

2880000

2900000

2920000

Base from NASA Goddard Media Studios Landsat 5 data

November10, 2011

Biscayne Bay

Biscayne domain

0 20 40 KILOMETERS

0 10 20 MILES

TTI domain

TIME domain

Lake Okeechobee

Florida Bay

Figure 1. Study area including Everglades National Park (Tides and Inflows of the Mangroves of the Everglades [TIME] 

model domain), Ten Thousand Islands (TTI model domain), and the eastern coastal area (Biscayne model domain). The 

Biscayne and TIME simulations were combined into the BISECT simulation.
Methods 3

Methods

A hindcast simulation was previously developed using 

the BISECT hydrologic model to assess the effects of the 

GMH. A detailed description of the BISECT model development can be found in Wang and others (2007) and Lohmann 

and others (2012). The development of the BISECT simulations including the hindcast period and the historical storm 

representation is described in Swain and others (2015). The 

repurposing of the hurricane simulation makes use of these 

simulation tools with further use of historical and recent data 

to model the effects of the GMH in its historical context. In 

both the recent and hindcast simulations, the surface features 

are roughly described on the 500-meter model grid scale, and 

the resolution of overland flow resistance, infiltration rate, 

and topography are limited to this scale. The flow in the canal 

system is not implicitly represented; instead, the water level in 

the canals is defined by user input for computation of groundwater leakage. The canal system’s effect on groundwater is 

represented along with the associated drainage of the system. 

The canal levee system, which affects overland flow, is also 

represented in the topography for the 1996–2004 simulation 

but is absent in the hindcast period. Coastal canal outflows are 

likewise defined by the user.

Previous Simulations

The GMH was represented in the hindcast 1926–1932 period

(hereinafter referred to as “hindcast simulation”) for the purposes of delineating the longer-term effects of the storm. This 

simulation period was later extended to the years 1926–1940. 

Although these later years are not essential to simulating the 

GMH, this longer simulation is used in this study. The variables of the GMH were developed from several sources; for 

example, wind field data from Hurricane Wilma in 2005 were 

used as surrogates for the unknown spatial distribution of wind 

in the GMH (Swain and others, 2015). The 2005 wind data 

were also useful to represent a Wilma-type storm strike in a 

simulation representing the recent period 1996–2004 (hereinafter referred to as “recent simulation”). These simulations 

were used to compare different parameterizations of the hurricane parameters and a Wilma-type storm replacing the GMH 

strike (Swain and others, 2015).

The primary differences between the 1926–1940 and 

1996–2004 simulations include the change in static parameters 

and the change in time-series parameters. The static parameters include the canal system (which expanded considerably 

during the intervening seven decades) and the topography. 

The only primary canals in place during the entire period 

1926–1940 were the Tamiami Canal, Miami Canal, and 

Snapper Creek Canal along with several shorter coastal canals 

further south (Renken and others, 2005; fig. 2). The expanded 

canal system also includes the coastal hydraulic structure 

discharges to Biscayne Bay, which were not operational in 

the hindcast simulation period. The unregulated outflows for 

the 1926–1940 period are represented by the mean flow rates 

for 1996–2004, the timeframe of the original BISECT model. 

The differences in topography between the 1926–1940 and 

1996–2004 simulations are predominantly along the eastern 

coast (fig. 2), and these model differences primarily reflect the 

resetting of coastal elevations in the model near modern canals 

to predevelopment values. With minimal historical data, no 

alterations were made in the western part of the study area, but 

the elevations near coastal canals were altered to match the 

adjacent model-cell elevations. This leveling process removes 

the levees and other elevation variations associated with the 

modern canals.

The time-series variables include tidal levels, surfacewater inflows, rainfall, evapotranspiration (ET), wind, and 

salinities. The tidal fluctuation is defined by the same frequency components in both the hindcast and recent simulations, but the mean tidal level is changed by the measured 

sea-level rise difference (Maul and Martin, 1993), which is 

approximately 18 centimeters (cm). The mean tidal levels 

computed for 1926 and 1932 are −0.390 meter (m) and 

−0.373 m (North American Vertical Datum of 1988 [NAVD 

88]), respectively, compared to a −0.20-m mean level for 

2004. The surface-water inflows occurring along the northern 

boundary are estimated for the hindcast simulation from a 

seasonal fit equation to Lake Okeechobee levels (Swain and 

others, 2015). Rainfall for the hindcast is obtained from two 

existing gages (Swain and others, 2015), but little specific 

information is available to define the boundary salinity, wind, 

and solar radiation (used to calculate ET). The boundary 

salinities are far enough from the shorelines to be reasonably 

defined as oceanic average values (Swain and others, 2019) 

for the recent period, which should be similar to the values for 

the hindcast period. The wind and solar radiation timeseries 

in the hindcast period is likely similar in intensity and directional variations to those of the recent period, but the ET rates 

are affected by land-cover vegetation (reflected as stomatal 

resistance in ET computations), which has certainly been 

reduced in the urban areas of this model between the hindcast 

and recent periods (Swain and others, 2019). There are no 

specific data for this area to modify stomatal resistance, and 

the long-term ET rate is less of a factor when analyzing the 

short-term effects of hurricane strikes; therefore, the stomatal 

resistance representation is left the same in the recent and 

hindcast simulations.

Comparisons of Storm Effects in Different 

Simulation Periods

The effect of climatic and anthropogenic changes on the 

impact of storm strikes is examined by simulating the GMH in 

differing time periods. The hindcast simulation is extended to 

the 1926–1940 period, and the representation of storm wind, 

rain, and tidal surge, as refined in the previously published 
4 Repurposing a Hindcast Simulation of the 1926 Great Miami Hurricane, South Florida

simulations, is applied on the simulation date September 18, 

1926. The BISECT model datasets are archived online 

(Swain, 2020).

This simulation of the historical GMH strike is compared 

with a revised recent simulation that represents the GMH 

strike on September 18, 1996. With the same storm wind, 

rain, and tidal surge height above the ambient sea level in both 

simulation periods, the comparison indicates how the changes 

to the south Florida coastal system between 1926 and 1996 

affect the impact of the same storm. These coastal system 

changes include sea-level rise, expansion of the canal system 

and inland water deliveries, topography in the built-up areas, 

and the timeseries of rainfall. The rainfall over the 1926–1940 

period averaged 157.6 centimeters per year (cm/yr), and the 

rainfall over the 1996–2004 period averaged 139.6 cm/yr. 

To determine which variables affect the hydrologic response 

of a particular storm, a third simulation was implemented 

that included all the parameters of the 1926–1940 simulation 

with the GMH, with the exception of the sea-level timeseries, 

which was set to the higher 1996–2004 values.

Coastal salinity and surface-water inundation are the most 

important characteristics of hydrologic response to storms in 

comparisons between simulation results for the three GMH 

scenarios: (1) hindcast inland system and hindcast sea level 

(HH simulation); (2) recent inland system and recent sea level 

(RR simulation); and (3) hindcast inland system and recent sea 

level (HR simulation). Three coastal areas in the southeastern 

coastal model domain were chosen for evaluation of salinity 

and inundation (fig. 3). From north to south, area A includes 

most of the coastal control structures in southern MiamiDade County in the recent period and, therefore, changes the 

most hydrologically between the hindcast and recent periods. 

Area B includes fewer control structures and has lower land 

elevations than area A. The southernmost area, C, contains the 

smallest inland portion of the three areas, includes the southernmost shoreline of Biscayne Bay, and contains parts of the 

offshore barrier islands.

Results

A comparison between the HH, RR, and HR simulations on the day before and the day after the hurricane strike 

indicates that inundation differences were minimal, even if the 

amount of storm-surge flooding was substantial. The inland 

extent of salinity increased substantially more in the RR and 

HR simulations than in the HH simulation, especially in area 

A (fig. 3). The salinity intrusion pattern was also similar in 

RR and HR, where the additional intrusion is most obvious 

C-111

EXPLANATION

Biscayne Bay

N

Miami Canal

Snapper Creek

Canal

Canals in 1926

Canals in 1996

BISECT model boundary

Elevation lowered from 

1926 to 1996 0 5 10 15 MILES

0 5 10 20 15 MILES

Tamiami CanalLevee 31N Levee 31W

Figure 2. The canal system and topography in the BISECT model area in 1926 and 1996, south Florida.
Results 5

in locations south of Florida City Canal (south part of area 

A; fig. 3). In area B, the post-hurricane salinity patterns are 

affected by the canals in the RR simulation, but HR still 

shows more salinity intrusion in the northern part of area 

B than the HH simulation. Higher sea level alone allows 

distinctly more salinity intrusion in the HR simulation than 

in the HH simulation.

Quantifying the simulated changes in the extent of 

inundation, inland salinity, and offshore salinity in response 

to these storm scenarios yields more extensive insight 

(table 1 and fig. 4). Comparisons in the three areas delineated (A, B, and C) in figure 3 indicate that, in areas A and 

B, the increase in inundation was greatest in the RR simulation, with a difference of more than 18 square kilometers 

(km2) between scenarios HR and RR in area B (table 1). 

However, as can be seen in figure 4, the RR simulation 

starts with a lower prehurricane inundation in area B than 

the other simulations. In area C, the increase in inundation 

was similar in all three simulations.

Increases in mean inland salinity in all areas due to 

the hurricane strike were 1.3 to 4.0 practical salinity units 

(PSU) higher in the RR and HR simulations than in the HH 

simulation (table 1). Comparing pre- and post-hurricane 

inland salinities (fig. 4) illustrates the similarity of the RR 

and HR responses to the hurricane in contrast to the HH 

simulation, indicating that mean sea level is a prominent 

factor when a hurricane moves salinity ashore. In general, 

small decreases in offshore salinity are indicated in all scenarios, do not demonstrate any distinctive patterns, and are 

likely related to rainfall runoff.

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

Great Miami hurricane, 1926–HH

Great Miami hurricane, 1996–RR

Great Miami hurricane, 1926, with modern sea level–HR

Before hurricane After hurricane

Florida City Canal Florida City Canal

Area of insets Biscayne Bay

MIAMI-DADE

COUNTY

Florida City 

canal

35

30

25

20

15

10

5

0

Dry

Salinity, in practical salinity units

UTM northing, in meters

UTM easting, in meters

2780000

2800000

2820000

2840000

2860000

480000 500000 520000 540000 560000 580000

Figure 3. Salinity and inundation in areas A, B, and C before 

and after the hindcast inland system and hindcast sea-level 

(HH) simulation; recent inland system and recent sea-level (RR) 

simulation; and hindcast inland system and recent sea-level (HR) 

simulation, south Florida.
6 Repurposing a Hindcast Simulation of the 1926 Great Miami Hurricane, South Florida

Discussion

The simulated changes in inundation and salinity can be 

used to draw several conclusions about the relations between 

long-term changes to the coastal hydrologic system during 

the entire 1926–1996 period and major storm impacts. The 

inundation change the day after the storm strike is not highly 

sensitive to the represented changes in the hydrologic system; however, the largest inundation increase for areas A and 

B is in the RR simulation (table 1) with its recent sea level. 

Simulation HH has less prehurricane inundation in area C 

than the RR and HR simulations (fig. 4), and therefore has 

a slightly larger inundation increase. However, the inland 

salinity data demonstrate differences between the three different simulations more clearly than the inundation data. The 

purpose of the HR simulation is to isolate the effects of mean 

sea-level changes by representing all 1926–1940 conditions 

except for the 1996–2004 sea level. The hurricane in the RR 

and HR simulations brings more salinity ashore than in the 

HH simulation, indicating that the primary factor affecting the 

difference in salinity between the three different simulations 

of the storm strike is the rise in sea level from the 1926–1940 

period to the 1996–2004 period. The simulated hydrologic 

differences between the 1926–1940 and 1996–2004 periods—

including expansion of the canal system, differences in inland 

water deliveries, topographic changes in the built-up areas, 

and differences in rainfall—have less of an effect on hurricaneinduced salinity intrusion than changes in mean sea level.

These results derived from the simulations are intuitively 

reasonable because the hydrologic differences, other than sea 

level, are not likely to strongly affect the inland intrusion of 

salinity from a short-term storm event. The results do suggest, 

however, that any mitigation efforts against increased storm 

surge effects due to sea-level rise would have to be far more 

substantial than any previous structural changes.

Model Limitations

In addition to the inherent limitations in the FTLOADDS 

code and the BISECT application of the code (Swain and others, 2019), several features of the specific storm representation 

limit the certainty of the solutions and conclusions.

1. Storm surge is approximated as a defined height above 

sea level, and the full fetch of the surge buildup is not 

well represented.

2. The flow in the canal system is not represented, and the 

water level in the canals is defined by user input. Coastal 

canal outflows are likewise user defined.

3. The surface features are roughly described on a 500-m 

grid scale, and the resistance to overland flow, infiltration rate, and small-scale topography are either estimated 

or below the resolution of the model.

Neither frictional resistance nor infiltration is changed between 

simulated 1926 and 1996 conditions, and only topography 

around canals is altered, as described previously. Although 

Table 1. Changes in inundation and salinity in three areas before and after the simulated Great Miami Hurricane of 1926, south Florida.

[km2, square kilometers; PSU, practical salinity units, HH, hindcast inland system and hindcast sea level; RR, recent inland system and recent sea level; HR, 

hindcast inland system and recent sea level]

Simulation

Area A

Inundation

change (km2)

Inland salinity change 

(PSU)

Offshore salinity change 

(PSU)

Great Miami Hurricane in 1926 (HH) 80.50 5.60 −1.09

Great Miami Hurricane in 1996 (RR) 86.00 8.23 −2.41

Great Miami Hurricane in 1926 with 1996 sea level (HR) 77.25 8.05 −0.89

Area B

Inundation

change (km2)

Inland salinity change 

(PSU)

Offshore salinity change 

(PSU)

Great Miami Hurricane in 1926 (HH) 37.50 4.01 −0.29

Great Miami Hurricane in 1996 (RR) 59.50 8.05 −1.84

Great Miami Hurricane in 1926 with 1996 sea level (HR) 41.25 7.14 0.05

Area C

Inundation

change (km2)

Inland salinity change 

(PSU)

Offshore salinity change 

(PSU)

Great Miami Hurricane in 1926 (HH) 54.75 5.95 −1.47

Great Miami Hurricane in 1996 (RR) 51.00 7.23 −0.53

Great Miami Hurricane in 1926 with 1996 sea level (HR) 51.25 7.45 −1.05
Summary 7

limited by these factors, the usefulness of the simulations is 

enhanced by the comparative nature of the results. Computing 

differences between two scenarios allows equivalent model 

errors in the scenarios to cancel each other out, which should 

indicate general trends more accurately.

The simulation results can be expanded temporally to 

examine other storm configurations at different historical 

times and better parameterize the relations between particular storms, time periods, sea-level rise, and storm effects. By 

specifying the configuration of the storm, a more quantitative 

result can be obtained, and the simulated storms can be rated 

and compared with the suite of known hurricane landfalls. In 

addition, actual and proposed water-management strategies 

can be applied to the model to better determine their relative impacts.

Sufficient information exists to approximate likelihoods of hurricane strikes of particular intensities, and this 

information can be coupled with the inundation and salinity 

simulations for a range of conditions. These efforts can produce a predictive tool to estimate future storm effects and the 

implications of anthropogenic changes.

Summary

A coupled hydrodynamic surface-water/groundwater 

model was used to simulate the hydrologic effects of the 

1926 Great Miami Hurricane (GMH) in a hindcast simulation 

for the period 1926–1940. The storm surge, wind field, and 

rainfall from the GMH storm were also hypothesized to have 

occurred in 1996, as part of a simulation of hydrologic conditions during 1996–2004 for which the canal-system layout, 

topography, water deliveries, and antecedent climatic conditions were markedly different than existed during the 1926 

0

50

100

150

200

250

0

2

4

6

8

10

12

14

0

5

10

15

20

25

30

35

40

Area A Area B Area C 

Average salinity in offshore area A Average salinity in offshore area B Average salinity in offshore area C

Average salinity in inland area A Average salinity in inland area B Average salinity in inland area C

Inundation in area A Inundation in area B Inundation in area C

EXPLANATION

Before hurricane

After hurricane

Great Miami 

hurricane

in 1929

Great Miami 

hurricane

in 1996

Great Miami 

hurricane

in 1926 with

modern sea level

Great Miami 

hurricane

in 1929

Great Miami 

hurricane

in 1996

Great Miami 

hurricane

in 1926 with

modern sea level

Great Miami 

hurricane

in 1929

Great Miami 

hurricane

in 1996

Great Miami 

hurricane

in 1926 with

modern sea level

Area, in square kilometers Salinity, in PSU Salinity, in PSU

Figure 4. Inundation and salinity before and after the simulated Great Miami Hurricane of 1926, south Florida. [HH, hindcast inland 

system and hindcast sea level; RR, recent inland system and recent sea level; HR, hindcast inland system and recent sea level; PSU, 

practical salinity units; see fig. 3 for locations of areas A, B, and C]
8 Repurposing a Hindcast Simulation of the 1926 Great Miami Hurricane, South Florida

GMH. Model results indicate that substantially more surfacewater salinity would have been brought ashore in the recent 

period than in the hindcast period.

A simulation of the effects of the hurricane strike was 

made under 1926 conditions with one difference—sea level 

was assumed to be at 1996 levels. The purpose of this simulation was to isolate the effect of sea-level change on the 

response of the hydrologic system to a powerful hurricane 

strike. The resulting pattern of surface-water salinity intrusion 

was similar to that of the 1996 simulated storm and indicates 

that sea-level rise between the hindcast and recent periods 

is the primary factor affecting salinity intrusion in the recent 

simulation. Moreover, the structural changes in the inland 

system, including canal-system design, topography, and water 

deliveries, did not substantially affect or mitigate the effects of 

sea level on the storm impacts.

Acknowledgments

The authors would like to thank the USGS Southeast 

Region for funding support that allowed us to continue our 

research to develop more insight into the hydrologic system.

References

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Lohmann, M.A., Mazzotti, F.J., and Rice, K.G., 2014, 

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crocodile populations in South Florida using a spatiallyexplicit, stage-based population model: Wetlands, v. 34, 

no. S1, suppl. 1, p. 213–224, accessed March 3, 2017, at 

https://doi.org/10.1007/s13157-012-0370-0.

Langevin, C.D., Swain, E.D., and Wolfert, M.A., 2005, 

Simulation of integrated surface-water/ground-water 

flow and salinity for a coastal wetland and adjacent estuary: Journal of Hydrology (Amsterdam), v. 314, no. 1-4, 

p. 212–234. [Also available at https://doi.org/10.1016/

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For more information about this publication, contact

Director, Caribbean-Florida Water Science Center 

U.S. Geological Survey 

4446 Pet Lane, Suite 108

Lutz, FL 33559

For additional information, visit

https://www.usgs.gov/centers/car-fl-water

Publishing support provided by Lafayette Publishing 

Service Center


Krohn and others—Repurposing a Hindcast Simulation of the 1926 Great Miami Hurricane, South Florida—OFR 2020–1010

ISSN 2331-1258 (online)

https://doi.org/10.3133/ofr20201010